Program Explanation Manual

Version 1.00 [ANDTR101]

March 2014

Renesas MCU Car Rally Secretariat

MCU Car Kit, Ver. 5.1

Program Explanation Manual

– kit12_rx62t Version

(Version for RX62T)

All trademarks and registered trademarks are the property of their respective owners.

Important Notice (Revision 1.2)

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Renesas MCU Car Rally Secretariat assumes no responsibility for any loss or damage that may arise due to

errors this manual may contain.

Other

The information contained in this manual is current as of the date of publication. The Renesas MCU Car Rally

Secretariat reserves the right to make changes to the information or specifications contained in this manual

without prior notice. Make sure to check the latest version of this manual before starting fabrication.

Contact Information

MCU Car Rally Secretariat, Renesas Solutions Corp.

MN Building, 2-1 Karuko-saka, Ageba-cho, Shinjuku-ku, Tokyo, 162-0824, Japan

Tel. (03) 3266-8510

E-mail: official@mcr.gr.jp

I

Contents

1. Overview of MCU Car Rally Kit Ver. 5.1 ................................................................................ 1

1.1. Exterior View of MCU Car Rally Kit Ver. 5.1 ........................................................................................... 1

1.2. Power Supply Configuration of Standard Kit ............................................................................................ 2

1.3. Power Supply Configuration with Boosted Drive Voltage ......................................................................... 3

2. Sensor Board Ver. 5 .................................................................................................................. 5

2.1. Specifications ............................................................................................................................................. 5

2.2. Circuit Diagram ......................................................................................................................................... 6

2.3. Dimensions ................................................................................................................................................ 7

2.4. Sensor Mounting Positions ........................................................................................................................ 7

2.5. Exterior View ............................................................................................................................................. 8

2.6. Relationship between the Sensor Board Ver.5 CN1 and the RMC-RX62T Board ..................................... 9

2.7. Method of Distinguishing Between White and Black Portions of the Course ......................................... 10

2.8. Method of Determining Whether Start Bar Is Open or Closed ................................................................ 10

2.9. Output signals of U8 and U9 ................................................................................................................... 11

2.10. Operating Principle of Circuit .................................................................................................................. 12

2.11. Sensor Adjustment Procedure .................................................................................................................. 13

3. Motor Drive Board Ver. 5 ....................................................................................................... 16

3.1. Specifications ........................................................................................................................................... 16

3.2. Circuit Diagram ....................................................................................................................................... 17

3.3. Dimensions .............................................................................................................................................. 18

3.4. External Appearance ................................................................................................................................ 19

3.5. Relationship between the Motor Drive Board Ver. 5 CN2 and the RMC-RX62T Board ......................... 21

3.6. Motor Control .......................................................................................................................................... 22

3.6.1. Role of the Motor Drive Board ................................................................................................... 22

3.6.2. Operating Principle of Speed Control ......................................................................................... 22

3.6.3. Operating Principle of Forward and Reverse .............................................................................. 23

3.6.4. Brake and free ............................................................................................................................. 24

3.6.5. H-bridge circuit ........................................................................................................................... 25

3.6.6. Using FETs as the Switches in an H-Bridge Circuit .................................................................... 25

3.6.7. P-Channel and N-Channel Short FETs Prevention Circuit .......................................................... 29

3.6.8. Free Circuit .................................................................................................................................. 32

3.6.9. Actual Circuit .............................................................................................................................. 33

3.6.10. Operation of Left Motor .............................................................................................................. 35

3.6.11. Operation of Right Motor ............................................................................................................ 35

3.7. Servo Control ........................................................................................................................................... 36

3.7.1. Operating Principle ..................................................................................................................... 36

3.7.2. Circuit .......................................................................................................................................... 37

3.8. LED Control ............................................................................................................................................ 37

3.9. Pushbutton Control .................................................................................................................................. 38

4. Sample Programs .................................................................................................................... 39

4.1. Program Development Environment ....................................................................................................... 39

4.2. Installing the Sample Programs ............................................................................................................... 39

4.3. Opening the kit12_rx62t Workspace ........................................................................................................ 41

4.4. Project ...................................................................................................................................................... 42

II

5. Program Explanation – kit12_rx62t.c ..................................................................................... 43

5.1. Program Code Listing .............................................................................................................................. 43

5.2. Differences between programs for kit07_rx62t.c and kit12_rx62t.c ........................................................ 53

5.3. On-Chip Peripheral Functions of RX62T MCU Used by the Program .................................................... 53

5.4. Program Explanation ............................................................................................................................... 54

5.4.1. Start ............................................................................................................................................. 54

5.4.2. Including External Files .............................................................................................................. 54

5.4.3. Symbol Definitions ..................................................................................................................... 54

5.4.4. Prototype Declarations ................................................................................................................ 56

5.4.5. Global Variable Declarations ....................................................................................................... 57

5.4.6. init Function(Clock Choice) ....................................................................................................... 58

5.4.7. init Function (Port I/O Settings) ................................................................................................. 58

5.4.8. init Function (Compare Match Timer Settings) .......................................................................... 61

5.4.9. init Function (Multi-Function Timer Pulse Unit 3 Settings) ....................................................... 62

5.4.10. Excep_CMT0_CMI0 Function (Interrupt Every 1 ms) ............................................................. 63

5.4.11. timer Function (Pause) ............................................................................................................... 64

5.4.12. sensor_inp Function (Read State of Sensors) ............................................................................. 65

5.4.13. check_crossline Function (Crossline Detection) ........................................................................ 72

5.4.14. check_rightline function (Right Half Line Detection) ............................................................... 74

5.4.15. check_leftline function (Left Half Line Detection) .................................................................... 75

5.4.16. dipsw_get Function (Reading DIP Switches) ............................................................................. 76

5.4.17. buttonsw_get Function (Reading the Pushbutton State in MCU board) .................................... 77

5.4.18. pushsw_get Function (Reading the Pushbutton State) ............................................................... 78

5.4.19. startbar_get Function (Reading the Start Bar Detection Sensor) .............................................. 79

5.4.20. led_out_m Function (LED Control in MCU board) ................................................................... 80

5.4.21. led_out Function (LED Control) ................................................................................................ 81

5.4.22. motor Function (Motor Speed Control) ..................................................................................... 82

5.4.23. handle Function (Servo Steering Operation) .............................................................................. 88

5.4.24. Start ............................................................................................................................................. 90

5.4.25. Patterns ........................................................................................................................................ 91

5.4.26. Writing a Program ....................................................................................................................... 91

5.4.27. Pattern Descriptions .................................................................................................................... 93

5.4.28. Initial while and switch when Using Patterns ............................................................................. 94

5.4.29. Pattern 0: Wait For Button Input ................................................................................................. 95

5.4.30. Pattern 1: Check if Start Bar Is Open .......................................................................................... 97

5.4.31. Pattern 11: Normal Trace............................................................................................................. 99

5.4.32. Pattern 12: Check End of Large Turn to Right .......................................................................... 110

5.4.33. Pattern 13: Check End of Large Turn to Left ............................................................................ 114

5.4.34. Crank Overview ........................................................................................................................ 119

5.4.35. Pattern 21: Processing at 1st Crossline Detection ..................................................................... 120

5.4.36. Pattern 23: Trace, Crank Detection After Crossline .................................................................. 122

5.4.37. Patterns 31 and 32: Clearing from Left Crank .......................................................................... 125

5.4.38. Patterns 41 and 42: Right Crank Clearing Processing ............................................................... 129

5.4.39. Right Lane Change Outline ....................................................................................................... 133

5.4.40. Pattern 51: Processing at 1st Right Half Line Detection ........................................................... 134

5.4.41. Pattern 53: Trace after Right Half Line ..................................................................................... 137

5.4.42. Pattern 54: Right Lane Change End Check ............................................................................... 139

5.4.43. Left Lane Change Outline ......................................................................................................... 141

5.4.44. Processing at 1st Left Half Line Detection ................................................................................ 142

5.4.45. Pattern 63: Trace after Left Half Line ....................................................................................... 145

III

5.4.46. Pattern 64: Left Lane Change End Check ................................................................................. 147

6. Adjusting the Servo Center and Maximum Turn Angle ....................................................... 149

6.1. Outline ................................................................................................................................................... 149

6.2. Install the communication program Tera Term ...................................................................................... 150

6.3. Adjusting the Servo Center .................................................................................................................... 154

6.4. Determining the Maximum Turning Angle of the Servo ....................................................................... 162

6.5. Overwriting the kit12_62t.c Program Code ........................................................................................... 168

7. Hints on Modifying the Program .......................................................................................... 170

7.1. Outline ................................................................................................................................................... 170

7.2. Examples of the MCU Car Going Off the Track ................................................................................... 171

7.2.1. Crossline Not Detected Correctly .............................................................................................. 171

7.2.2. Crank Not Detected Correctly ................................................................................................... 172

7.2.3. Half Line Not Detected Correctly ............................................................................................. 174

7.2.4.

After Clearing from Crank, MCU Car Mistakes Outer White Line for Center Line and Goes off Track

.. 175

7.2.5. End of Lane Change Not Detected Correctly ............................................................................ 178

7.3. Conclusion ............................................................................................................................................. 179

8. Calculating the Left-Right Motor Speed Differential ........................................................... 180

8.1. Calculation Method ................................................................................................................................ 180

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

1

1. Overview of MCU Car Rally Kit Ver. 5.1

1.1. Exterior View of MCU Car Rally Kit Ver. 5.1

Left rear wheel

Sensor board Ver. 5

Flat cable B

Motor drive board Ver. 5

Right motor

Left motor

Control battery box

Drive battery box

Servo

Right rear wheel

Right front wheel

Left front wheel

RMC-RX62T MCU board

Drive power supply switch

Control power supply switch

Flat cable A

The MCU Car Rally Kit Ver. 5.1, comprises a control system consisting of the RMC-RX62T board (a MCU board

with an RX62T MCU mounted on it), the sensor board Ver. 5, and the motor drive board Ver. 5, and a drive system

consisting of the right motor, the left motor, and the servo.

Right motor

Left motor

Sensor board Ver. 5

8-bit

RMC-RX62T

MCU board

Motor drive board

Ver.5

8-bit

Servo

Port 4

Port 7

(bit 0 to 6)

Port 0

(bit 0)

SW

LED2

LED3

Flat

cable

A

8 sensors for monitoring the course

1 sensor for monitoring the start bar

CN2

CN3

Flat

cable

B

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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RMC-RX62T

MCU board

The MCU board reads the state of the sensors via port 4, calculates the PWM output values for

the right and left motors and the turn angle for the servo, and outputs this data to the motor

drive board connected to port 7. The manner in which output values for the motors and servo

are decided, based on the state of the sensors, is determined by the software program.

Sensor board

Ver. 5

8 sensors which detect state of the course are here. They output “0” if bottom of the sensor is

white, and output “1” if it is black.

※The program inverts the signal, and it judges white is “1” and black is “0”.

There is one sensor which detects if there is the start bar or not. It outputs “0” if the start bar is

present, and output “1” if it is absent.

※The rightmost course state detection sensor and start bar detection sensor have an OR

relationship connected to bit 0. The rightmost sensor is initially not responding because only

the middle of the board should be able to detect the start line, leaving the board able to judge

the state of the start bar. After the start, the board does not to look for the start bar and therefore

can instead detect the track using the rightmost sensor on the board’s underside.

Motor drive

board Ver. 5

The motor drive board converts low-power signals from the MCU board into high-power

signals that operate the motors. The motor power supply is also used to drive the servo.

A pushbutton is connected to the motor drive board, and the software program is written such

that pressing this button starts the MCU car. There are also two LEDs mounted on the motor

drive board for debugging.

Batteries

 Control (MCU) power supply: Four size AA rechargeable batteries (1.2 V × 4 = 4.8 V) are

used.

 Drive (motor and servo) power supply: Four size AA rechargeable batteries or four size AA

alkaline batteries (1.5 V × 4 = 6.0 V) are used.

Note: Ensure that the voltage of the control system is 4.0 V to 5.5 V.

1.2. Power Supply Configuration of Standard Kit

The standard kit uses separate power supplies for the control and drive blocks. This ensures that the MCU will not

be reset due to low power no matter how much current the motors and servo consume.

The power supply configuration of the standard kit is shown below.

Right motor

Left motor

5 V

Control power

supply of MCU,

sensor, and motor

drive boards

4 AA batteries

Drive power

supply for right

and left motors

and servo

4 AA batteries

5 V

Sensor board

Ver. 5

Motor drive

board Ver. 5

7

6

5

2

1

0

3

0

RMC-RX62T

MCU board

P9

Servo

5 V

P4

PB

micro

SD

P7

and

P0

4

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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The flow of current from the power supplies is shown below.

1.3. Power Supply Configuration with Boosted Drive Voltage

It is possible to increase the speed of the motors by boosting the drive voltage (increasing the number of batteries).

Using six batteries as the motor power supply increases the voltage to 7.2 V, and using eight batteries increases it

to 9.6 V. Note, however, that the maximum number of batteries allowed is eight. This means it is necessary for the

control and drive blocks to use a common power supply. Applying a voltage of 9.6 V to the motors will not wreck

them (though it is not really desirable, since their rated voltage is 6 V), but the MCU has a guaranteed

operating voltage range of 4.0 V to 5.5 V and applying a voltage exceeding 5.5 V will cause it to stop

operating. (The absolute maximum voltage rating is 6.5 V. Applying a voltage in excess of 6.5 V will destroy

the MCU.) In like manner, the voltage applied to the servo must not exceed 6 V. It is therefore necessary to

install a three-pin regulator to bring the MCU and servo voltage down to the rated level. Note that when a

common power supply is used, the MCU will be reset if the voltage drops below 4.0 V due to large current

consumption by the motors, etc. It is necessary to be careful regarding MCU resets when using a common power

supply.

When the LM350 add-on set is installed and a power supply voltage of 6 V or greater is used, the LM2940-5

generates a 5 V voltage for the control block, including the MCU, and the LM350 generates a 6 V voltage for the

servo.

Right motor

Left motor

9.6 V

Sensor board

Ver.5

RMC-RX62T

MCU board

Motor drive board

Ver.5

P9

P7

and

P0

7

6

5

2

1

0

4

0

5 V control power supply and 6 V

servo power supply generated by

3-pin regulator

LM350 add-on set

+

5.0 V

9.6 V

Common power supply

8 batteries

Servo

6 V

P4

PB

3

RMC-RX62T

MCU board

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

4

The flow of current from the power supplies is shown below.

Note: The springs in the battery box of the kit are weak, and this can cause the battery terminals to become

disconnected from the battery box contacts when the MCU car accelerates or decelerates. This can reset the

MCU (due to a disconnection of several tens of milliseconds). This problem can be prevented by using a

battery box that holds the batteries firmly in place.

RMC-RX62T

MCU board

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

5

2. Sensor Board Ver. 5

2.1. Specifications

The specifications of the sensor board Ver. 5 are shown below.

Name

Sensor Board Ver. 5

Abbreviation

Sensor Board 5

Contained in kit

MCU car kit Ver. 5.1

Date released for sale

Jun 2013 (Still available as of September 2013.)

Number of boards

1

Number of sensors for monitoring course

8

Number of sensors for monitoring start bar

1

Signal inverter circuit

None (inversion performed by software program)

Connections to MCU board

RX62T: Port4

Voltage

DC5.0 V ±10%

Weight (actual measured weight of completed board)

Approx. 18 g

Resist (board colour)

Black

Board dimensions

W 140 × D 38 × T 1.2 mm

Dimensions (actual measured dimensions)

Max. W 140 × D 38 × H 14 mm

Note: The weight will vary depending on factors such as the length of the lead wires and the amount of solder

used.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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2.2. Circuit Diagram

The 9th pin of CN1 doubles as below.

・Detect the color of the course at

rightmost

・Detect the start bar

It used for whether there is a start bar

before start, and used for detection of

the color of the course after start. It is

unknown which sensor reacts by this

circuit.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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2.3. Dimensions

The sensor board has a total of 22 mounting holes, 11 on the right and 11 on the left. These holes are used to

secure the sensor board in place.

2.4. Sensor Mounting Positions

Eight sensors are used to detect the black and white portions of the course. These are mounted on the board in the

positions indicated below.

Note: Sensor mounting positions on sensor board Ver.5 for reference

Infrared LED

Modulation-type photosensor

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

8

2.5. Exterior View

Front of board

VR 1,2,3,4,5,6,7,8,9

Volume for setting

sensor sensitivity

LED 1,3,5,7,9,11,13,15,17

LED for confirming of

sensor sensitivity

CN1

Connector for sensor

signal outputs

Back of board

U 1,2,3,4,5,6,7,8

Modulation type photsensor (for course)

LED 2,4,6,8,10,12,14,16

Infrared LED (for course)

U9

Modulation type photosensor (for start bar)

LED18

Infrared LED (for start bar)

1

2

9

10

CN2

Connector for output of sensor

signal of detect start bar.

(It needs pattern cut for use)

Polyester pile tape

T

he following shows the connection of connectors and the content of signals:

Parts number

Item

Description

CN1

Connector

(connect to

MCU board)

Item reference

CN2

Connector

(option)

The signal of rightmost of the course state detection sensor doubles as the

signal of the start bar detection sensor. It can let CN2 become independent

and output the signal of the start bar detection sensor.

In addition, it needs to implement the parts (R9, R10, LED17) to let the start

bar detection sensor become independent.

For more details, refer to Sensor Board Ver.5 Assembly Manual.

LED2,4,6,8,

10,12,14,16

Infrared LED

The TLN119 element is used. It emits infrared light. Since the light emitted

is in the infrared range, it is not visible to humans. There are eight infrared

LEDs for course detection.

LED18

Infrared LED

The TLN119 element is used. There is an infrared LED for start bar

detection..

U1,2,3,4,

5,6,7,8

Modulation type

photosensor

The S7136 element (for course) from Hamamatsu Photonics K.K. is used.

Light emitted by the infrared LED is picked up by this element. When

infrared light is detected, the current portion of the course is determined to

be white. When no infrared light is detected, the current portion of the course

is determined to be black. There are eight modulation type photosensors.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

9

U9

Modulation type

photosensor

The S6846 element (for start bar) from Hamamatsu Photonics K.K. is used.

Light emitted by the infrared LED is picked up by this element. When

infrared light is detected, it is determined that there is a start bar present.

When no infrared light is detected, it determined that there is no start bar

present.

VR1,2,3,4,

5,6,7,8

Volume for

adjusting sensor

sensitivity

(for course)

The amounts of light output from infrared LEDs are adjusted in these

volumes. Some portions of the MCU car course are grey. By adjusting the

sensitivity with the volume, it is possible to make the grey areas be detected

as white or as black. The standard software program assumes that grey areas

will be detected as white.

VR9

Volume for

adjusting sensor

sensitivity

(for start bar)

The amount of light output from LED18 is adjusted using these volumes. If

there is a start bar, it becomes white. If there is not a start bar, there will be

no reflection. Adjust this volume to react (for turn lights LED15) when there

is a start bar.

LED1,3,5,7,

9,11,13,15

LED for

confirming sensor

sensitivity

The LED lights when white is detected and is dark when black is detected.

The LED is used for confirmation when adjusting the sensitivity with the

variable resistor.

－

Polyester pile tape

Polyester pile tape is mounted on the solder side of the sensor board and is

made a constant height so as to not rub the course and the sensor directly and

also to allow the sensor to react appropriately.

2.6. Relationship between the Sensor Board Ver.5 CN1 and the RMC-RX62T Board

The Sensor Board Ver. 5 connector CN1 and the RMC-RX62T board connector CN2 (port 4) must be connected

with a 10-pin flat cable. The following table lists the signals carried by this cable.

RMC-RX62T

Board CN2

Signal

Direction

Motor Driver

Board Ver.5 CN1

Description

Pin 1 (+5V)

－

Pin 1

It provides +5V±10%（4.5～5.5V） to the circuits of the Sensor

Board Ver.5.

Pin 2 (P47)

←

Pin 2

Inputs a signal from U1 (The first sensor from left）

"0"：White (LED1 on) "1"：Black (LED1 off)

Pin 3(P46)

←

Pin 3

Inputs a signal from U2（The second sensor from left）

"0"：White (LED3 on) "1"：Black (LED3 off)

Pin 4(P45)

←

Pin 4

Inputs a signal from U3 (The third sensor from left）

"0"：White (LED5 on) "1"：Black (LED5 off)

Pin 5(P44)

←

Pin 5

Inputs a signal from U4 (The fourth sensor from left）

"0"：White (LED7 on) "1"：Black (LED7 off)

Pin 6(P43)

←

Pin 6

Inputs a signal from U5 (The fourth sensor from right）

"0"：White (LED9 on) "1"：Black (LED9 off)

Pin 7(P42)

←

Pin 7

Inputs a signal from U6（The third sensor from right）

"0"：White (LED11 on) "1"：Black (LED11 off)

Pin 8(P41)

←

Pin 8

Inputs a signal from U7(The second sensor from right)

"0"：White (LED13 on) "1"：Black (LED13 off)

Pin 9 (P40)

←

Pin 9

Inputs a signal from U8（The first sensor from right） and a signal

from U9（Sensor which detect start bar）.

"0"：White (LED15 on) "1"：Black (LED15 off)

or

"0"：There is start bar (LED15 on) "1"：none (LED15 off).

Because the car initially sits on the middle of the course, U8 (The

first sensor from right) detects black at the start. The data from U9

(start bar) is then checked. After the start the start bar will not be

present and the activity of U8(course) is used.

Pin10 (GND)

－

Pin 10

GND

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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2.7. Method of Distinguishing Between White and Black Portions of the Course

The sensor board is equipped with eight pairs of elements, each pair comprising one element that shines infrared

light onto the course and one element that detects reflected infrared light. The system makes use of the fact that

white areas reflect light and black areas absorb it. The emitter element is used to shine infrared light onto the

course. When this infrared light is reflected back and detected by the receiver element, the current portion of the

course is determined to be white. When no infrared light is detected, the current portion of the course is

determined to be black.

The amount of infrared light emitted can be adjusted by using a variable resistor. Some portions of the MCU car

course are grey. By adjusting the sensitivity with the variable resistor, it is possible to make the grey areas be

detected as white or as black. The standard software program assumes that grey areas will be detected as

white.

2.8. Method of Determining Whether Start Bar Is Open or Closed

Initially, the white start bar is closed. An infrared LED and S6846 (modulation type photo sensor) are mounted on

the board facing forward. The following is determined based on the sensor state.

●Start bar closed

Light is reflected

↓

Start bar is there

Light receiving element

Light emitting element

On

Sensitivity setting

●Start bar open

No light is reflected

↓

No start bar there

Off

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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2.9. Output signals of U8 and U9

Output of sensor is open collector output, and connects NPN type transistor (type 2SC ). Pin 9 of CN1 doubles as

output of the sensor which detects the rightmost course sensor (U8) and the sensor which detects the start bar, as in

the circuit below.

The behaviour of 2 sensors and output signals are as shown below.

Sensor which

detect the course

Sensor which

detect the start bar

Circuit

Output

Mind

Black

absent

open

(High impedance)

In fact, it outputs 5V

after being pulled up.

Black

present

0V

The start bar

detection sensor is

judged to be present if

it is 0V before start.

White

absent

0V

The course state

detection judges the

surface to be white if

it is 0V

after start.

White

present

0V

Never both states – OR

system.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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2.10. Operating Principle of Circuit

1. U1 is a photo sensor. It combines a light receiver and an infrared LED oscillator circuit.

2. Pin 1 of U1 is connected to an infrared LED (LED2). The infrared light emitted by LED2 is received by U1.

VR1 is used to adjust the brightness of the infrared LED.

3. The signal indicating whether or not infrared light is being received is output on pin 3 of U1. This pin is

connected to an LED (LED1), providing a visual confirmation of whether the signal value is 0 or 1.

4. When light from the infrared LED reaches U1 (course white), 0 is output. The anode of the LED is positive

and the cathode is negative, causing the LED to light.

5. When no light from the infrared LED reaches U1 (course black), 1 is output. (See below for details.) The

anode of the LED is positive and the cathode is also positive, so the LED is dark.

6. It is stated above that 1 is output when no light reaches U1, but in fact pin 3 of U1 is an open collector output.

“Open collector output” means a value of 0 = 0 V and any other value is open, a state in which the pin is not

connected to anything. In the digital world, there are no values other than 0 and 1. Therefore, a resistor (RA1)

is used to pull up the signal, resulting in a value of 1 when the photosensor is open.

Note: Operating Principle of Modulation  Type Photosensor (S7136) for Reference

(from the Product Data Sheet)

(a) Oscillator and Timing Signal Generator Circuit

The reference oscillator output is obtained by charging and discharging the built-in

capacitor with a constant current. The oscillator output is input to the timing signal

generator circuit, which produces the LED drive pulses and the timing pulses used

for digital signal processing.

(b) LED Drive Circuit

This circuit uses the LED drive pulses produced by the timing signal generator circuit

to drive a light emitting diode. The drive duty ratio is 1/16.

(c) Photodiode and Preamp Circuit

The photodiode is of the on-chip type. The photoelectric current from the photodiode

is converted into a voltage by the preamp circuit. An independent AC amplifier circuit

is used as the preamp circuit. In addition to expanding the dynamic range through

increased tolerance for DC and low-frequency ambient light, it boosts the signal

detection sensitivity.

(d) C-Coupling, Buffer Amplifier, and Reference Voltage Circuit

A C-coupling is used to further remove the effects of low-frequency ambient light and

to eliminate the DC offset from the preamp. The signal is boosted to the comparator

level by the buffer amplifier, and the comparator-level signal is generated by the

reference voltage circuit.

(e) Comparator Circuit

The comparator circuit has an added hysteresis function to prevent chattering

caused by tiny fluctuations in the input light.

(f) Signal Processing Circuit

The signal processing circuit comprises a gate circuit and a digital integrating circuit.

The gate circuit prevents malfunctions due to non-synchronous ambient light by

distinguishing the input signal during synchronous detection. Since the gate circuit

cannot eliminate synchronous ambient light, the digital integrating circuit does so at

a later stage.

(g) Output Circuit

This circuit buffers the output from the signal processing circuit and outputs it

externally.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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2.11. Sensor Adjustment Procedure

1

※View from side

As shown in the photo, place the

MCU car such that the edge of

the sensor board is parallel with

the grey line at the centre of the

track. Place the MCU car on a

surface that is the same level as

the track, just as if it was

running on the course.

2

※View from side

If you try to adjust the sensors by

holding the MCU car in your

hand as shown here, the results

will not be satisfactory because

of the unevenness of the gap

between the sensors and the

track surface. Make sure to

place the MCU car on a

surface that is the same level as

the track

3

Turn all nine of the variable

resistors all the way

counter clockwise.

NO!

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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4

Align the horizontal line on the

board with the line where the

white and grey stripes on the

track meet. Look straight down

from above when doing the

alignment.

5

Turn each of the eight variable

resistors clockwise until the

corresponding LED lights. Turn

each variable resistor slowly

and stop turning the moment

the LED lights. Next, adjust the

variable resistors so that the

sensors also react to the grey

stripe. The MCU car kit

should be adjusted so the

sensors react to both the white

and grey stripes.

6

Move the sensors back slightly.

The LEDs should all go dark.

7

Once again, slowly move the

sensors in parallel toward the

grey stripe. If one of the LEDs

lights before the others, lower its

sensitivity (turn the variable

resistor counter clockwise). If an

LED does not light, increase its

sensitivity (turn the variable

resistor clockwise). Repeat the

adjustments several times until

all the LEDs light at about the

same time.

VR9 is for start bar. We do not adjust it now

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

15

8

Next, we will adjust the sensor

that detects the start bar.

Stand a vertical white panel or

sheet of paper several

centimetres away from the front

of the sensor board. This white

panel or sheet of paper will be a

substitute for the start bar.

Confirm that under the

rightmost sensor which detects

the course is black and LED15

is off at that time.

9

Slowly turn VR9, indicated by

the circle ○, clockwise until

LED15 lights and then stop

turning it.

Adjust that under LED 15 is

black because it doubles as the

rightmost of the course state

sensor .

If the LED goes dark when the

white panel or sheet of paper is

removed, the adjustment is

complete.

Approx. 1cm

LED of bit 0 ON

VR9

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

16

3. Motor Drive Board Ver. 5

3.1. Specifications

The table below lists the specifications of the motor driver board Ver. 5.

Motor Drive Board Ver. 5

Abbreviation

Drive board 5

Number of components

Components with leads: 66

The component lead pitches are 2.54 mm or greater

Connection to the RMC-RX62T board

Connection using port 7 and bit 0 of port 1

Motors controlled

Two motors (the left and right motors)

Servos controlled

One motor

LEDs turned on/off under program control

Two motors

Pushbutton switches

One switch

Control system voltage

(voltage that can be applied to CN2)

DC5.0 V 10 %

Drive system voltage

(voltage that can be applied to CN1)

4.5 to 5.5 V or 7 to 15 V

Note, however, that if 7 V or higher is used the voltages applied to

the microcontroller board and servo board must be limited to 5 V

and 6 V respectively with the LM350 Add-On Set.

Servo and motor control period

Motor: 16 ms, Servo: 16 ms

Individual setting of these values is not possible.

Motor free-running control

Supported by the addition of the Free-Running Add-On Set.

Note: There are two motor stop modes: Brake and Free.

See the sections on the Free-Running Add-On Set

for details.

Board dimensions

80 × 65 × 1.6 mm (W × D × T)

Dimensions when completed (actual

dimensions)

80 × 65 × 20 mm (W × D × H)

Weight

About 33 g

Note: The weight varies with the length of the lead wires

and the amount of solder used.

Standard software

RX62T microcontroller: kit12_rx62t.c

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.2. Circuit Diagram

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.3. Dimensions

The motor drive board has six mounting holes. These holes are used to secure the motor drive board to the rest of

the MCU car rally kit.

8 0

6 5

3 0

7 0

φ3.5-6

1 0 5

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.4. External Appearance

The photo below shows the external appearance of the motor drive board Ver. 5.

1

2

9

10

1(-)

CN2

Motor driver board control connector

CN3

Motor free-running

control connector

2(+)

3(-)

2(+)

1(PWM)

CN1

Power supply

connection

1

2

CN4

Servo

connector

CN5

Left motor connector

JP1

PWM signal

selection

LED3

ON/OFF

Controllable

programmatically

SW1

Push

switch

1

2

CN6

Right motor connector

JP2

Servo power

supply selection

LED2

ON/OFF

Controllable

programmatically

LED1

Always on when

power is applied

Note: Two-pin connectors CN1, CN5, and CN6 have been changed from IL connectors manufactured by

Japan Aviation Electronics Industry, Ltd., to XH connectors manufactured by J.S.T. Mfg. Co., Ltd.

This means that the female connectors must be changed as well.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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The following table lists the connector connections and the contents carried by these signals.

Part No.

Connects To

Pins

Description

CN1

Power supply input

1

GND

2

The + power supply connection (4.5 to 5.5 V or 7 to 15 V)

Note: However, that if 7 V or higher is used, the LM350

Add-On Set must be installed.

CN2

Connects to MCU

board

1 to 10

See next page.

CN3

Connected to the

microcontroller board

1

+5 V

2

Left motor stop state selection. 1: Free, 0: Brake

3

Right motor stop state selection. 1: Free, 0: Brake

4

GND

CN4

Servo

1

Servo PWM signal output

2

Servo power supply (6 V output)

3

GND

CN5

Left motor

1, 2

Left motor output

CN6

Right motor

1, 2

Right motor output

JP1

PWM signal selection

of left motor

1～6

This jumper switches PWM output terminal and direction selection

terminal.

●RMC-RX62T board and RY_R8C38 Board

Short (done on the solder side)

・Between pin 1-3 short

・Between pin 2-4 short

・Between pin 3-5 no connection

・Between pin 4-6 no connection

※It has been short-circuited on the solder side.

No need to do in anything in particular.

●RY3048FoneBoard

Cut (solder side)

・Between pin 1-3 pattern cut (solder side)

・Between pin 2-4 pattern cut (solder side)

・Between pin 3-5 short

・Between pin 4-6 short

JP2

Servo power supply

switching

1 to 3

This jumper switches the source for power supply to the servo

power supply pin (pin 2 on CN2).

 If the supply voltage provided to CN1 is under 6 V

Short pins 1 and 2 together. Connect the CN1 power supply

directly to pin 2 on CN2.

 If the supply voltage provided to CN1 is over 6 V

Since this would exceed the voltage that can be applied to the

servo, the components from the LM350 Add-On Set must be

installed and pins 2 and 3 shorted together. A 6 V level will be

supplied to pin 2 on CN2 through the LM350 3-terminal

regulator.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.5. Relationship between the Motor Drive Board Ver. 5 CN2 and the RMC-RX62T

Board

The motor drive board Ver. 5 connector CN2 and the RMC-RX62T board connector CN3 (port 7 and bit 0 of port 1)

must be connected with a 10-pin flat cable. The following table lists the signals carried by this cable.

RMC-RX62T

Board CN3

Signal

Direction

Motor Drive Board

Ver. 5 CN2

Description

Pin 1 (+5 V)



Pin 1

This is the +5 V level provided to the control system circuits,

including the Motor Drive Board Ver. 5 and logic ICs.

Regardless of whether or not the LM350 Add-On Set is used,

this is always a 5 V source.

 If the control system and drive system power supplies are

separate (the LM350 Add-On Set is not used)

Here, a 5 V level is supplied to the Motor Drive Board Ver.

5 from the RMC-RX62T board.

 If the control system and drive system share a power supply

(the LM350 Add-On Set is used)

The Motor Drive Board Ver. 5 control system circuits and

the RMC-RX62T board are supplied from the Motor Driver

Board Ver. 5 LM2940-5 (a 5 V output 3-terminal

regulator).

Pin 2 (P1_0)



Pin 2

Connected to LED 2.

0: LED on, 1: LED off

Pin 3 (P7_6)



Pin 3

Connected to LED 3.

0: LED on, 1: LED off

Pin 4 (P7_5)



Pin 6

Controls the right motor direction of rotation.

0: Forward, 1: Reverse

Pin 5 (P7_4)



Pin 8

Controls the left motor direction of rotation.

0: Forward, 1: Reverse

Pin 6 (P7_3)



Pin 5

Outputs a PWM signal to the right motor.

Pin 7 (P7_2)



Pin 7

Outputs a PWM signal to the left motor.

Pin 8 (P7_1)



Pin 4

Outputs a PWM signal to the servo.

Pin 9 (P7_0)



Pin 9

Detects the state of the pushbutton switch.

0: Pressed, 1: Released

Pin 10 (GND)



Pin 10

GND

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.6. Motor Control

3.6.1. Role of the Motor Drive Board

The motor drive board operates the motors according to instructions received from the MCU. The signals from the

MCU meaning “run motor” or “stop motor” are very weak, so the motors will not operate if they are connected

directly to the signal lines. The motor drive board converts the weak signals into signals with a large current level

of several hundred to several thousand milliamperes (mA) in order to operate the motors.

MCU board

M

Signal is too weak to operate motor.





MCU board

M

Converted to large current to drive motor!

○

Motor drive

board

3.6.2. Operating Principle of Speed Control

To make a motor run, it is enough to apply a current. To make it stop, cease supplying the current. But how do you

regulate the speed to, say, 10% or 20% of the maximum? How do you make fine adjustments to the speed at which

the motor operates?

A variable resistor can be used to reduce the voltage. But since a large current flows to the motor, a very large

resistance would be required. In addition, the voltage not applied to the motor would be converted to heat by the

resistor.

A better way to control the speed of the motor is to switch the power on and off repeatedly at high speed,

producing an effect that is equivalent to applying an intermediate voltage. The signal on and off states are

controlled by using a fixed cycle and altering the ratio of on and off. This control method is called “pulse width

modulation,” abbreviated as PWM control. The proportion of the pulse width for which the signal is on is called

the duty cycle. If the on-width is 50% of the cycle, the duty cycle is 50%. This can also be simplified to “PWM

50%” or just “motor 50%.”

Pulse width

On width

Off width

Duty cycle = on-width / pulse width (on-width + off-width). For example, if the pulse duration is 100 ms and the

on-width is 60 ms, duty cycle = 60 ms / 100 ms = 0.6 = 60%. If the signal is on for the entire pulse duration, the

duty cycle is 100%. If it is off for the entire pulse duration, the duty cycle is 0%.

“PWM” sounds complicated, but a simple arrangement like that shown below, in which you control the speed by

repeatedly connecting and disconnecting a motor and a battery with a wire, can also be considered an example of

PWM. The longer you keep the wire connected, the faster the motor runs. The longer the periods it is disconnected,

the slower it gets. A person can repeat this connect, disconnect operation at intervals of a couple of seconds, but

the MCU can accomplish it at intervals of a few milliseconds.

Battery

OFF

Motor

ON

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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Let’s assume a waveform consisting of output at 0 V and 5 V. The longer the on-duration is during each cycle, the

higher the average voltage value, as shown in the figure below. If output is at 5 V for the entire cycle, the average

voltage value is 5 V, as you would expect. This is the maximum voltage. What if the signal is on 50% of the time?

This works out to an average of 5 V × 0.5 = 2.5 V, so the result is the same as changing the voltage.

In this way, if we reduce the on-duration of each cycle to 90%, 80%, and so on down to 0%, the result is

equivalent to gradually lowering the voltage until we finally reach 0 V.

By connecting this signal output to a motor, we can change the motor’s speed a little bit at a time, making precise

speed control possible. If we connect the signal output to an LED, we can change the brightness of the LED. A

MCU is capable of performing this operation in microsecond or millisecond increments. Control on this order

enables extremely smooth motor control.

25%

50%

75%

100%

0%

Duty cycle

1 cycle

1.25 V

2.5 V

3.75 V

5 V

0 V

＝

Converted voltage

equivalent

0 V

5 V

0 V

5 V

0 V

5 V

0 V

5 V

0 V

5 V

Why would we want to use pulse width control rather than voltage control to regulate the speed of a motor? MCUs

are very good at handling digital values expressed as zeroes and ones. They are less good at dealing with analogue

values such as voltages. This is why we use a system of changing the width of the zeroes and ones to simulate

controlling the voltage. The system is called PWM control.

3.6.3. Operating Principle of Forward and Reverse

The motor drive board, Ver. 5, can control the forward, reverse, and brake operation of the motors. The voltages

applied to the motor terminals for forward and reverse control are shown in the table below.

Forward

Reverse

Voltages

applied to

motor

terminals

M

1

2

Pin 1 is connected to GND (0 V) and pin 2 to a

positive voltage.

M

1

2

Pin 1 is connected to GND (0 V) and pin 2 to a

positive voltage.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.6.4. Brake and free

Stopping and slowing the car with the normal circuit of the Motor drive board Ver.5 is done by breaking. With the

free addition set added, there are two methods of halting the car, break and free.

The difference of brake and free is as shown below.

Brake

Free

Voltages

applied to

motor

terminals

Ｍ

1

2

Brake

GND

Connect both terminals to GND. As a result,

both terminals are short-circuited.

Ｍ

1

2

Free

No

connection

GND

Make one side connectionless.

Falling of

speed

(image)

Speed

Time

Forward

Brake

Time

Forward

Speed

Free

As for the free, the slowdown of the stop is slower than brakes. Use the free for the cases that want to cut down

speed slowly.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.6.5. H-bridge circuit

How does this actually work? Four switches are arranged with the motor in the centre, forming an H-pattern, as

shown in the figure below. Forward, reverse, brake, and free control is accomplished by turning these four

switches on and off in specific combinations. The name “H-bridge circuit” refers to the circuit’s H-pattern.

10 V

M

Forward

10 V

M

Reverse

10 V

M

Brake

10 V

M

Free

3.6.6. Using FETs as the Switches in an H-Bridge Circuit

Field-effect transistors (FETs) are used as the switches. A P-channel FET (2SJ type) is used on the positive side of

the power supply and an N-channel FET (2SK type) on the negative side.

A P-channel FET allows current to flow between drain and source (D-S) when the gate voltage (VG) is less than

the source voltage (VS).

An N-channel FET allows current to flow between drain and source (D-S) when the gate voltage (VG) is greater

than the source voltage (VS).

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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Forward, reverse, and brake operations are performed by changing the voltages applied to the gates of the four

FETs.

Reverse

10V

0V

Forward

0V

10V

Brake

10V

Free

10V

0V

10V

One point to keep in mind is that the two FETs on the right side or the two FETs on the left side must never both

be on at the same time. Having both on at the same time connects the 10 V and GND pins with no load at all,

which is the same as shorting them. This could cause the FETs or the trace patterns to burn out, which would be

dangerous.

A look at the four gate voltages reveals that the same voltage is applied to the P-channel and N-channel FETs on

the right side and to the P-channel and N-channel FETs on the left side. Therefore, we tried using the circuit

shown below.

When we actually input a PWM waveform to the circuit, the FETs became very hot. Why might this be?

We might assume that in on-off switching of the channel between drain and source when signals are input to the

gates of the FETs, the P-channel and N-channel FETs would respond instantly as in the Ideal Waveforms figure at

A

B

Operation

0 V

Brake

0 V

10 V

Reverse

10 V

0 V

Forward

10 V

Brake

Note: When a power supply voltage of

10 V is input to the G (gate) pin,

that voltage is either applied

unchanged to the motor or a

voltage of 0 V is applied. Note that

the voltage applied to the motor

differs depending on whether the

value of the control signal is 0 or 1.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

27

left, resulting in smooth switching between brake and forward operation. In fact, however, the FETs do not operate

instantly and there is a time delay. This delay is greater when the FET switches from on to off than when it

switches from off to on. Therefore, there is a short duration during which both FETs are in the on state, as shown

in the Actual Waveforms figure at right. This state is equivalent to a short circuit.

Motor

Brake

Forward

Brake

Gate

P-ch FET

operation

Nch FET

operation

ON

OFF

ON

OFF

Ideal Waveforms

Motor

Brake

Forward

Brake

Gate

P-ch FET

operation

NchFET

operation

ON

OFF

ON

OFF

Actual Waveforms

200 ns

87 ns

120 ns

225 ns

Short circuit

The delay between the on signal and the start of the response is called the “turn-on delay,” the duration from the

start of the on response to the actual on state is the “rise time,” the delay between the off signal and the start of the

response is the “turn-off delay,” and the duration from the start of the off response to the actual off state is the “fall

time.”

Thus, the actual duration from off to on is the turn-on delay plus the rise time, and the actual duration from on to

off is the turn-off delay plus the fall time. These are the delays shown in the figure at right above.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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The electrical characteristics of the FETs used on the motor drive board, 2SJ530 and 2SK2869 from Renesas

Electronics, are shown below.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.6.7. P-Channel and N-Channel Short FETs Prevention Circuit

As a solution, instead of turning the P-channel and N-channel FETs on side A on and off at the same time as in the

previous circuit diagram, we will introduce a short time shift to prevent the formation of a short circuit.

Motor

Forward

Brake

Forward

X

(PchIN)

Y

(NchIN)

PchFET

operation

NchFET

operation

ON

OFF

ON

OFF

Both sides do not turn on at the same time

OFF

10 V

0 V

10 V

0 V

The delay is generated by an integrating circuit. There are many technical books available with information on

integrating circuits, and we refer you to them if you wish to learn more. A diagram of the integrating circuit is

shown below.

The delay time is calculated as follows:

The time constant T = CR [s].

In the present case, the figures are 9.1 kΩ and 4700 pF, so the calculation is as follows:

T = 9.1 × 103 × 4,700 × 10-12 = 42.77 [μs].

The 74HC series treats an input voltage

of 3.5 V or more as 1. By measuring

actual waveforms, we determined that

the time required to reach 3.5 V is

approximately 50 μs.

Though the maximum shift is 225 ns in

the Actual Waveforms figure above, we

decided to generate a delay of 50 μs

with the integrating circuit. This is to

accommodate delay from voltage

conversion digital transistors other than

FETs, as well as delay from

capacitance components in the FET

gates.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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A circuit diagram combining an integrating circuit and the FETs is shown below.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

31

(1) Changing from Brake to Forward Operation

1. At point A, a 0 signal corresponds to brake and a 1 signal to forward. The output changes from 0 (brake) to

1 (forward) at point A.

2. At point B, the integrating circuit outputs a waveform with a 50 μs delay.

3. An A-and-B waveform is output from point C.

4. An A-or-B waveform is output from point D.

5. A signal that has been voltage converted by the digital transistor is output from point E. The 0 V-5 V signal

from point C has been converted to a 10 V-0 V signal.

6. In like manner, a 10 V-0 V signal converted from the 0 V-5 V signal from point D is output from point F.

7. When the signal at point A changes from 0 to 1, the gate voltage of FET2 changes from 10 V to 0 V and

FET2 turns off. However, it does not enter the off state immediately due to the delay. Both FET1 and FET2

are off at the point, and the motor is in the free state.

8. The gate voltage of FET1 changes from 10 V to 0 V 50 μs after the signal at point A changes, and FET1

turns on. A voltage of 10 V is applied to the motor, causing it to run in the forward direction.

(2) Changing from Forward to Brake Operation

1. When the signal at point A changes from 1 (forward) to 0 (brake), the gate voltage of FET1 changes from 0

V to VBAT and FET1 turns off. However, it does not enter the off state immediately due to the delay. Both

FET1 and FET2 are off at this point, and the motor is in the free state.

2. The gate voltage of FET2 changes from 0 V to 10 V 50 μs after the signal at point A changes, and FET2

turns on. A voltage of 0 V is applied to both terminals of the motor, causing it to perform brake operation.

In this way, a short circuit is prevented when switching between operations by turning both FETs off for a

short time and putting the motor into the free state.

Note: In this example the voltage applied to the gates is 10 V. In actual practice, the voltage matches the power

supply voltage (VBAT).

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.6.8. Free Circuit

The free circuit described here is not for the purpose of preventing shorting of the P-channel and N-channel FETs.

Rather, it is used to put the motors into the free or brake state when stopped.

By installing the free add-on set on the motor drive board, Ver. 5, it is possible to select between free and brake

states when the motors are stopped. The state when the value of point G is 1 is shown below.

Motor

Free

Forward

Free

A

B

C

= A and B

A

D

= G or B = 1

1 (5 V)

0

E

(PchIN)

作

F

(NchIN)

FET1

operation

FET2

operation

ON

OFF

ON

OFF

10 V

0 V

10 V

0 V

Free

Output

voltage

10 V

Free

50 s

1 (5 V)

0

1 (5 V)

0

1 (5 V)

0

50 s

Integrating

circuit

Voltage

conversion

FET

Motor

Always OFF

Always 1

When the value of point G is 1, the value of point D is always 1 regardless of the states of points A or B. This

means that FET2 is always off and the motor changes repeatedly between the forward and free states.

When the value of point G is 0, the motor changes repeatedly between the forward and brake states, as above.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.6.9. Actual Circuit

The actual circuit configuration adds a forward/reverse switching circuit to the integrating circuit, FET circuit, and

free circuit described above. The circuit configuration for the left motor is shown below. The following three pins

are used.

 P72: Pin for applying PWM signal

 P74: Forward/reverse switching pin

 P51: Brake/free switching pin

(1) Circuit Diagram

(2) Direction: Forward, Stop: Signal Levels and Motor Operation in Brake State

A

B

C

FET1

gate

FET2

gate

FET3

gate

FET4

gate

Pin 2 of

CN5

Pin 1 of

CN5

Motor

Operation

0

10 V

(OFF)

10 V

(ON)

10 V

(OFF)

10 V

(ON)

0 V

Brake

0

1

10 V

(OFF)

0 V

(OFF)

10 V

(OFF)

10 V

(ON)

Free

(Open)

0 V

Free

1

0 V

(ON)

0 V

(OFF)

10 V

(OFF)

10 V

(ON)

10 V

0 V

Forward

0

1

10 V

(OFF)

0 V

(OFF)

10 V

(OFF)

10 V

(ON)

Free

(Open)

0 V

Free

0

10 V

(OFF)

10 V

(ON)

10 V

(OFF)

10 V

(ON)

0 V

Brake

Note: A, B, C： 0 = 0 V, 1 = 5 V

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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(3) Direction: Reverse, Stop: Signal Levels and Motor Operation in Brake State

A

B

C

FET1

gate

FET2

gate

FET3

gate

FET4

gate

Pin 2 of

CN5

Pin 1 of

CN5

Motor

Operation

0

1

10 V

(OFF)

10 V

(ON)

10 V

(OFF)

10 V

(ON)

0 V

Brake

0

1

10 V

(OFF)

10 V

(ON)

10 V

(OFF)

0 V

(OFF)

0 V

Free

(Open)

Free

1

10 V

(OFF)

10 V

(ON)

0 V

(ON)

0 V

(OFF)

0 V

10 V

Reverse

0

1

10 V

(OFF)

10 V

(ON)

10 V

(OFF)

0 V

(OFF)

0 V

Free

(Open)

Free

0

10 V

(OFF)

10 V

(ON)

10 V

(OFF)

10 V

(ON)

0 V

Brake

(4) Direction: Forward, Stop: Signal Levels and Motor Operation in Free State

A

B

C

FET1

gate

FET2

gate

FET3

gate

FET4

gate

Pin 2 of

CN5

Pin 1 of

CN5

Motor

Operation

0

1

0

10 V

(OFF)

0 V

(OFF)

10 V

(OFF)

10 V

(ON)

Free

(Open)

0 V

Free

0

1

10 V

(OFF)

0 V

(OFF)

10 V

(OFF)

10 V

(ON)

Free

(Open)

0 V

Free

1

0 V

(ON)

0 V

(OFF)

10 V

(OFF)

10 V

(ON)

10 V

0 V

Forward

0

1

10 V

(OFF)

0 V

(OFF)

10 V

(OFF)

10 V

(ON)

Free

(Open)

0 V

Free

0

1

10 V

(OFF)

0 V

(OFF)

10 V

(OFF)

10 V

(ON)

Free

(Open)

0 V

Free

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.6.10. Operation of Left Motor

The left motor is controlled by three pins: P74, P72, and P51. If the free add-on set is not installed, the value of

P5_1 is always 0.

Left Motor

Direction

P74

Left Motor PWM

P72

Left Motor Stop

Operation

P51

Motor Operation

0

PWM

0

PWM = 1: forward, PWM = 0: brake

0

PWM

1

PWM = 1: forward, PWM = 0: free

1

PWM

0

PWM = 1: reverse, PWM = 0: brake

1

PWM

1

PWM = 1: reverse, PWM = 0: free

To operate the left motor in the forward and brake states, set P74 to 0 and P51 to 0 and input a PWM waveform on

P72. The left motor will run forward according to the PWM ratio. For example, when the PWM ratio is 0% the

motor will be stopped, when PWM ratio is 50% the motor will run forward at 50% voltage, and when the PWM

ratio is 100% the motor will run forward at 100% voltage. In this case the motor is in the brake state when

stopped.

3.6.11. Operation of Right Motor

The right motor is controlled by three pins: P75, P73, and P50. If the free add-on set is not installed, the value of

P50 is always 0.

Right Motor

Direction

P75

Right Motor

PWM

P73

Right Motor Stop

Operation

P50

Motor Operation

0

PWM

0

PWM = 1: forward, PWM = 0: brake

0

PWM

1

PWM = 1: forward, PWM = 0: free

1

PWM

0

PWM = 1: reverse, PWM = 0: brake

1

PWM

1

PWM = 1: reverse, PWM = 0: free

To operate the right motor in the forward and free states, set P75 to 0 and P50 to 1 and input a PWM waveform on

P73. The right motor will run forward according to the PWM ratio. For example, when the PWM ratio is 0% the

motor will be stopped, when PWM ratio is 50% the motor will run forward at 50% voltage, and when the PWM

ratio is 100% the motor will run forward at 100% voltage. In this case the motor is in the free state when stopped.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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3.7. Servo Control

3.7.1. Operating Principle

Pulses with a cycle of 16 ms are applied to the servo, and the servo angle is determined by the pulse on-width.

There is some variation among servo manufacturers and individual devices in the correspondence between the

servo turn angle and the pulse on-width, but generally speaking the correspondence is roughly a shown below.

 The cycle is 16 ms.

 The Centre position corresponds to a pulse on-width of 1.5 ms, and a change of ±0.8 ms produces a change in

the servo angle of ±90 degrees.

The PWM signals for servo control are generated in the reset-synchronized PWM mode of the RX62T MCU.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

37

3.7.2. Circuit

1. The PWM signal is output on bit 1 of port 7. The on-width is changed by changing the value of MTU3.TGRD

in the software.

2. A transistor with an internal resistor between the port and pin 1 of the servo acts as a buffer. If bit 1 of port 7

and pin 1 of the servo were connected directly, the MCU port could be destroyed if, for example, the power

supply were accidentally connected to pin 1 or if noise were introduced. This would be fatal. In contrast, the

transistor with internal resistor can be replaced easily if it is destroyed.

3. Pin 2 connects to the servo’s power supply. If the motor drive power supply uses four or fewer batteries, short

JP2 and the pin above it for a direct connection to the power supply. A motor drive power supply voltage

higher than that produced by four batteries exceeds the rating of the servo, so it is necessary in this case to use

the LM350 3-pin regulator, which has a 3 A current flow, to fix the voltage at 6 V. In this case, short JP2 and

the pin below it.

3.8. LED Control

Three LEDs are mounted on the motor drive board. Of these, two can be turned on and off by the MCU.

The cathode of each LED is connected directly to a port of the MCU. The current limiting resistance is 1 kΩ.

A current of 20 mA can be input to the EBR3338S with a forward voltage of 1.7 V. The current limiting resistance

is calculated as follows:

Resistance = (power supply voltage – voltage applied to LED) / current to be input to the LED

= (5 – 1.7) / 0.02

= 165 Ω

In practice, a 1 kΩ resistor is connected to reduce battery current consumption and limit the current flowing

through the port. The current is calculated as follows:

Current = (power supply voltage – voltage applied to LED) / resistance

= (5 – 1.7) / 1,000 = 3.3 [mA]

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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When 0 is output to P10, the voltage on the

LED cathode side becomes 0 V, current flows,

and the LED lights.

When 1 is output to P10, the voltage on the LED cathode

side becomes 5 V, the potential difference between the two

terminals of the LED is 0 V, and the LED does not light.

3.9. Pushbutton Control

One pushbutton is mounted on the motor drive board.

The pushbutton is pulled up by a

10 kΩ resistor and is connected to

bit 0 of port 7.

When the pushbutton is not

depressed, 1 is input to P70 via the

pull-up resistor.

When the pushbutton is depressed,

0 is input to P70 via the ground

(GND).

0 V

5 V

Lit!

Dark

No current

flow!

"0"

ON

"1"

OFF

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

39

4. Sample Programs

4.1. Program Development Environment

The Renesas integrated development environment is used for program development. For instructions on installing

and using the Renesas integrated development environment, see Renesas Integrated Development Environment

Operation Manual (Version for RX62T).

4.2. Installing the Sample Programs

Note: Continue with step 3, if you have CD-R for this seminar.

1

Get the Sample Program

(workspace_rx62t_100_eng.exe) from the

Renesas site.

Renesas Electronics

http:¥www.renesas.com/company_info/carr

ally/

Click Download

2

Download workspace_rx62t_100_eng.exe

3

Run workspace_rx62t_100_eng.exe.

Please execute

"workspace_rx62t_100_eng.exe " in the

following folder, if you have CD-R for this

seminar.

"CD-R drive:¥ 04-Programs"

4

The installed file is in "C:¥WorkSpace".

Click OK.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

40

5

Installation has been completed.

Click This program installed correctly.

6

Open The "C:¥Workspace" folder

There is the operation test program at the

folder "kit12_rx62t".

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

41

4.3. Opening the kit12_rx62t Workspace

1

Launch the Renesas integrated development

environment.

2

Select Browse to another project

workspace.

3

Select kit12_rx62t.hws from the

C:¥Workspace¥kit12_rx62t folder.

4

The kit12_rx62t workspace opens.

kit12_rx62t

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

42

4.4. Project

One project is registered in the kit12_rx62t workspace.

Project

Contents

kit12_rx62t

This is the MCU car running program. The explanation of this program starts in the

next section of this manual.

kit12test_rx62t

This is a program for testing the components of the completed MCU car, such as

the motor drive board and sensor board, to see if they operate correctly.

For details, please refer to "Operation Test Manual MCU Car Kit, Ver.5.1 (RX62T

Version)".

sioservo1_62t

This is the program for adjusting the servo centre.

For details, please refer to "6. Adjusting the Servo Centre and Maximum Turn

Angle".

sioservo2_62t

This is the program for determining the maximum turning angle of the servo.

For details, please refer to "6. Adjusting the Servo Centre and Maximum Turn

Angle".

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5. Program Explanation – kit12_rx62t.c

5.1. Program Code Listing

A code listing of the program that controls the MCU car by using the RX62T MCU appears below.

1 : /***********************************************************************/

2 : /* Supported Microcontroller:RX62T */

3 : /* File: kit12_rx62t.c */

4 : /* File Contents: MCU Car Trace Basic Program(RX62T version) */

5 : /* Version number: Ver.1.00 */

6 : /* Date: 2013.09.01 */

7 : /* Copyright: Renesas Micom Car Rally Secretariat */

8 : /***********************************************************************/

9 : /*

10 : This program supports the following boards:

11 : * RMC-RX62T board

12 : * Sensor board Ver. 5

13 : * Motor drive board Ver. 5

14 : */

15 :

16 : /*======================================*/

17 : /* Include */

18 : /*======================================*/

19 : #include "iodefine.h"

20 :

21 : /*======================================*/

22 : /* Symbol definitions */

23 : /*======================================*/

24 :

25 : /* Constant settings */

26 : #define PWM_CYCLE 24575 /* Motor PWM period (16ms) */

27 : #define SERVO_CENTER 2300 /* Servo center value */

28 : #define HANDLE_STEP 13 /* 1 degree value */

29 :

30 : /* Masked value settings X:masked (disabled) O:not masked (enabled) */

31 : #define MASK2_2 0x66 /* X O O X X O O X */

32 : #define MASK2_0 0x60 /* X O O X X X X X */

33 : #define MASK0_2 0x06 /* X X X X X O O X */

34 : #define MASK3_3 0xe7 /* O O O X X O O O */

35 : #define MASK0_3 0x07 /* X X X X X O O O */

36 : #define MASK3_0 0xe0 /* O O O X X X X X */

37 : #define MASK4_0 0xf0 /* O O O O X X X X */

38 : #define MASK0_4 0x0f /* X X X X O O O O */

39 : #define MASK4_4 0xff /* O O O O O O O O */

40 :

41 : /*======================================*/

42 : /* Prototype declarations */

43 : /*======================================*/

44 : void init(void);

45 : void timer( unsigned long timer_set );

46 : unsigned char sensor_inp( unsigned char mask );

47 : unsigned char startbar_get( void );

48 : int check_crossline( void );

49 : int check_rightline( void );

50 : int check_leftline( void );

51 : unsigned char dipsw_get( void );

52 : unsigned char buttonsw_get( void );

53 : unsigned char pushsw_get( void );

54 : void led_out_m( unsigned char led );

55 : void led_out( unsigned char led );

56 : void motor( int accele_l, int accele_r );

57 : void handle( int angle );

58 :

59 : /*======================================*/

60 : /* Global variable declarations */

61 : /*======================================*/

62 : unsigned long cnt0;

63 : unsigned long cnt1;

64 : int pattern;

65 :

66 : /***********************************************************************/

67 : /* Main program */

68 : /***********************************************************************/

69 : void main(void)

70 : {

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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71 : /* Initialize MCU functions */

72 : init();

73 :

74 : /* Initialize micom car state */

75 : handle( 0 );

76 : motor( 0, 0 );

77 :

78 : while( 1 ) {

79 : switch( pattern ) {

80 :

81 : /****************************************************************

82 : Pattern-related

83 : 0: wait for switch input

84 : 1: check if start bar is open

85 : 11: normal trace

86 : 12: check end of large turn to right

87 : 13: check end of large turn to left

88 : 21: processing at 1st cross line

89 : 22: read but ignore 2nd time

90 : 23: trace, crank detection after cross line

91 : 31: left crank clearing processing ? wait until stable

92 : 32: left crank clearing processing ? check end of turn

93 : 41: right crank clearing processing ? wait until stable

94 : 42: right crank clearing processing ? check end of turn

95 : 51: processing at 1st right half line detection

96 : 52: read but ignore 2nd line

97 : 53: trace after right half line detection

98 : 54: right lane change end check

99 : 61: processing at 1st left half line detection

100 : 62: read but ignore 2nd line

101 : 63: trace after left half line detection

102 : 64: left lane change end check

103 : ****************************************************************/

104 :

105 : case 0:

106 : /* Wait for switch input */

107 : if( pushsw_get() ) {

108 : pattern = 1;

109 : cnt1 = 0;

110 : break;

111 : }

112 : if( cnt1 < 100 ) { /* LED flashing processing */

113 : led_out( 0x1 );

114 : } else if( cnt1 < 200 ) {

115 : led_out( 0x2 );

116 : } else {

117 : cnt1 = 0;

118 : }

119 : break;

120 :

121 : case 1:

122 : /* Check if start bar is open */

123 : if( !startbar_get() ) {

124 : /* Start!! */

125 : led_out( 0x0 );

126 : pattern = 11;

127 : cnt1 = 0;

128 : break;

129 : }

130 : if( cnt1 < 50 ) { /* LED flashing processing */

131 : led_out( 0x1 );

132 : } else if( cnt1 < 100 ) {

133 : led_out( 0x2 );

134 : } else {

135 : cnt1 = 0;

136 : }

137 : break;

138 :

139 : case 11:

140 : /* Normal trace */

141 : if( check_crossline() ) { /* Cross line check */

142 : pattern = 21;

143 : break;

144 : }

145 : if( check_rightline() ) { /* Right half line detection check */

146 : pattern = 51;

147 : break;

148 : }

149 : if( check_leftline() ) { /* Left half line detection check */

150 : pattern = 61;

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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151 : break;

152 : }

153 : switch( sensor_inp(MASK3_3) ) {

154 : case 0x00:

155 : /* Center -> straight */

156 : handle( 0 );

157 : motor( 100 ,100 );

158 : break;

159 :

160 : case 0x04:

161 : /* Slight amount left of center -> slight turn to right */

162 : handle( 5 );

163 : motor( 100 ,100 );

164 : break;

165 :

166 : case 0x06:

167 : /* Small amount left of center -> small turn to right */

168 : handle( 10 );

169 : motor( 80 ,67 );

170 : break;

171 :

172 : case 0x07:

173 : /* Medium amount left of center -> medium turn to right */

174 : handle( 15 );

175 : motor( 50 ,38 );

176 : break;

177 :

178 : case 0x03:

179 : /* Large amount left of center -> large turn to right */

180 : handle( 25 );

181 : motor( 30 ,19 );

182 : pattern = 12;

183 : break;

184 :

185 : case 0x20:

186 : /* Slight amount right of center -> slight turn to left */

187 : handle( -5 );

188 : motor( 100 ,100 );

189 : break;

190 :

191 : case 0x60:

192 : /* Small amount right of center -> small turn to left */

193 : handle( -10 );

194 : motor( 67 ,80 );

195 : break;

196 :

197 : case 0xe0:

198 : /* Medium amount right of center -> medium turn to left */

199 : handle( -15 );

200 : motor( 38 ,50 );

201 : break;

202 :

203 : case 0xc0:

204 : /* Large amount right of center -> large turn to left */

205 : handle( -25 );

206 : motor( 19 ,30 );

207 : pattern = 13;

208 : break;

209 :

210 : default:

211 : break;

212 : }

213 : break;

214 :

215 : case 12:

216 : /* Check end of large turn to right */

217 : if( check_crossline() ) { /* Cross line check during large turn */

218 : pattern = 21;

219 : break;

220 : }

221 : if( check_rightline() ) { /* Right half line detection check */

222 : pattern = 51;

223 : break;

224 : }

225 : if( check_leftline() ) { /* Left half line detection check */

226 : pattern = 61;

227 : break;

228 : }

229 : if( sensor_inp(MASK3_3) == 0x06 ) {

230 : pattern = 11;

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

46

231 : }

232 : break;

233 :

234 : case 13:

235 : /* Check end of large turn to left */

236 : if( check_crossline() ) { /* Cross line check during large turn */

237 : pattern = 21;

238 : break;

239 : }

240 : if( check_rightline() ) { /* Right half line detection check */

241 : pattern = 51;

242 : break;

243 : }

244 : if( check_leftline() ) { /* Left half line detection check */

245 : pattern = 61;

246 : break;

247 : }

248 : if( sensor_inp(MASK3_3) == 0x60 ) {

249 : pattern = 11;

250 : }

251 : break;

252 :

253 : case 21:

254 : /* Processing at 1st cross line */

255 : led_out( 0x3 );

256 : handle( 0 );

257 : motor( 0 ,0 );

258 : pattern = 22;

259 : cnt1 = 0;

260 : break;

261 :

262 : case 22:

263 : /* Read but ignore 2nd line */

264 : if( cnt1 > 100 ){

265 : pattern = 23;

266 : cnt1 = 0;

267 : }

268 : break;

269 :

270 : case 23:

271 : /* Trace, crank detection after cross line */

272 : if( sensor_inp(MASK4_4)==0xf8 ) {

273 : /* Left crank determined -> to left crank clearing processing */

274 : led_out( 0x1 );

275 : handle( -38 );

276 : motor( 10 ,50 );

277 : pattern = 31;

278 : cnt1 = 0;

279 : break;

280 : }

281 : if( sensor_inp(MASK4_4)==0x1f ) {

282 : /* Right crank determined -> to right crank clearing processing */

283 : led_out( 0x2 );

284 : handle( 38 );

285 : motor( 50 ,10 );

286 : pattern = 41;

287 : cnt1 = 0;

288 : break;

289 : }

290 : switch( sensor_inp(MASK3_3) ) {

291 : case 0x00:

292 : /* Center -> straight */

293 : handle( 0 );

294 : motor( 40 ,40 );

295 : break;

296 : case 0x04:

297 : case 0x06:

298 : case 0x07:

299 : case 0x03:

300 : /* Left of center -> turn to right */

301 : handle( 8 );

302 : motor( 40 ,35 );

303 : break;

304 : case 0x20:

305 : case 0x60:

306 : case 0xe0:

307 : case 0xc0:

308 : /* Right of center -> turn to left */

309 : handle( -8 );

310 : motor( 35 ,40 );

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

47

311 : break;

312 : }

313 : break;

314 :

315 : case 31:

316 : /* Left crank clearing processing ? wait until stable */

317 : if( cnt1 > 200 ) {

318 : pattern = 32;

319 : cnt1 = 0;

320 : }

321 : break;

322 :

323 : case 32:

324 : /* Left crank clearing processing ? check end of turn */

325 : if( sensor_inp(MASK3_3) == 0x60 ) {

326 : led_out( 0x0 );

327 : pattern = 11;

328 : cnt1 = 0;

329 : }

330 : break;

331 :

332 : case 41:

333 : /* Right crank clearing processing ? wait until stable */

334 : if( cnt1 > 200 ) {

335 : pattern = 42;

336 : cnt1 = 0;

337 : }

338 : break;

339 :

340 : case 42:

341 : /* Right crank clearing processing ? check end of turn */

342 : if( sensor_inp(MASK3_3) == 0x06 ) {

343 : led_out( 0x0 );

344 : pattern = 11;

345 : cnt1 = 0;

346 : }

347 : break;

348 :

349 : case 51:

350 : /* Processing at 1st right half line detection */

351 : led_out( 0x2 );

352 : handle( 0 );

353 : motor( 0 ,0 );

354 : pattern = 52;

355 : cnt1 = 0;

356 : break;

357 :

358 : case 52:

359 : /* Read but ignore 2nd time */

360 : if( cnt1 > 100 ){

361 : pattern = 53;

362 : cnt1 = 0;

363 : }

364 : break;

365 :

366 : case 53:

367 : /* Trace, lane change after right half line detection */

368 : if( sensor_inp(MASK4_4) == 0x00 ) {

369 : handle( 15 );

370 : motor( 40 ,31 );

371 : pattern = 54;

372 : cnt1 = 0;

373 : break;

374 : }

375 : switch( sensor_inp(MASK3_3) ) {

376 : case 0x00:

377 : /* Center -> straight */

378 : handle( 0 );

379 : motor( 40 ,40 );

380 : break;

381 : case 0x04:

382 : case 0x06:

383 : case 0x07:

384 : case 0x03:

385 : /* Left of center -> turn to right */

386 : handle( 8 );

387 : motor( 40 ,35 );

388 : break;

389 : case 0x20:

390 : case 0x60:

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

48

391 : case 0xe0:

392 : case 0xc0:

393 : /* Right of center -> turn to left */

394 : handle( -8 );

395 : motor( 35 ,40 );

396 : break;

397 : default:

398 : break;

399 : }

400 : break;

401 :

402 : case 54:

403 : /* Right lane change end check */

404 : if( sensor_inp( MASK4_4 ) == 0x3c ) {

405 : led_out( 0x0 );

406 : pattern = 11;

407 : cnt1 = 0;

408 : }

409 : break;

410 :

411 : case 61:

412 : /* Processing at 1st left half line detection */

413 : led_out( 0x1 );

414 : handle( 0 );

415 : motor( 0 ,0 );

416 : pattern = 62;

417 : cnt1 = 0;

418 : break;

419 :

420 : case 62:

421 : /* Read but ignore 2nd time */

422 : if( cnt1 > 100 ){

423 : pattern = 63;

424 : cnt1 = 0;

425 : }

426 : break;

427 :

428 : case 63:

429 : /* Trace, lane change after left half line detection */

430 : if( sensor_inp(MASK4_4) == 0x00 ) {

431 : handle( -15 );

432 : motor( 31 ,40 );

433 : pattern = 64;

434 : cnt1 = 0;

435 : break;

436 : }

437 : switch( sensor_inp(MASK3_3) ) {

438 : case 0x00:

439 : /* Center -> straight */

440 : handle( 0 );

441 : motor( 40 ,40 );

442 : break;

443 : case 0x04:

444 : case 0x06:

445 : case 0x07:

446 : case 0x03:

447 : /* Left of center -> turn to right */

448 : handle( 8 );

449 : motor( 40 ,35 );

450 : break;

451 : case 0x20:

452 : case 0x60:

453 : case 0xe0:

454 : case 0xc0:

455 : /* Right of center -> turn to left */

456 : handle( -8 );

457 : motor( 35 ,40 );

458 : break;

459 : default:

460 : break;

461 : }

462 : break;

463 :

464 : case 64:

465 : /* Left lane change end check */

466 : if( sensor_inp( MASK4_4 ) == 0x3c ) {

467 : led_out( 0x0 );

468 : pattern = 11;

469 : cnt1 = 0;

470 : }

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471 : break;

472 :

473 : default:

474 : /* If neither, return to standby state */

475 : pattern = 0;

476 : break;

477 : }

478 : }

479 : }

480 :

481 : /***********************************************************************/

482 : /* RX62T Initialization */

483 : /***********************************************************************/

484 : void init(void)

485 : {

486 : // System Clock

487 : SYSTEM.SCKCR.BIT.ICK = 0; //12.288*8=98.304MHz

488 : SYSTEM.SCKCR.BIT.PCK = 1; //12.288*4=49.152MHz

489 :

490 : // Port I/O Settings

491 : PORT1.DDR.BYTE = 0x03; //P10:LED2 in motor drive board

492 :

493 : PORT2.DR.BYTE = 0x08;

494 : PORT2.DDR.BYTE = 0x1b; //P24:SDCARD_CLK(o)

495 : //P23:SDCARD_DI(o)

496 : //P22:SDCARD_DO(i)

497 : //CN:P21-P20

498 : PORT3.DR.BYTE = 0x01;

499 : PORT3.DDR.BYTE = 0x0f; //CN:P33-P31

500 : //P30:SDCARD_CS(o)

501 : //PORT4:input //sensor input

502 : //PORT5:input

503 : //PORT6:input

504 :

505 : PORT7.DDR.BYTE = 0x7e; //P76:LED3 in motor drive board

506 : //P75:forward reverse signal(right motor)

507 : //P74:forward reverse signal(left motor)

508 : //P73:PWM(right motor)

509 : //P72:PWM(left motor)

510 : //P71:PWM(servo motor)

511 : //P70:Push-button in motor drive board

512 : PORT8.DDR.BYTE = 0x07; //CN:P82-P80

513 : PORT9.DDR.BYTE = 0x7f; //CN:P96-P90

514 : PORTA.DR.BYTE = 0x0f; //CN:PA5-PA4

515 : //PA3:LED3(o)

516 : //PA2:LED2(o)

517 : //PA1:LED1(o)

518 : //PA0:LED0(o)

519 : PORTA.DDR.BYTE = 0x3f; //CN:PA5-PA0

520 : PORTB.DDR.BYTE = 0xff; //CN:PB7-PB0

521 : PORTD.DDR.BYTE = 0x0f; //PD7:TRST#(i)

522 : //PD5:TDI(i)

523 : //PD4:TCK(i)

524 : //PD3:TDO(o)

525 : //CN:PD2-PD0

526 : PORTE.DDR.BYTE = 0x1b; //PE5:SW(i)

527 : //CN:PE4-PE0

528 :

529 : // Compare match timer

530 : MSTP_CMT0 = 0; //CMT Release module stop state

531 : MSTP_CMT2 = 0; //CMT Release module stop state

532 :

533 : ICU.IPR[0x04].BYTE = 0x0f; //CMT0_CMI0 Priority of interrupts

534 : ICU.IER[0x03].BIT.IEN4 = 1; //CMT0_CMI0 Permission for interrupt

535 : CMT.CMSTR0.WORD = 0x0000; //CMT0,CMT1 Stop counting

536 : CMT0.CMCR.WORD = 0x00C3; //PCLK/512

537 : CMT0.CMCNT = 0;

538 : CMT0.CMCOR = 96; //1ms/(1/(49.152MHz/512))

539 : CMT.CMSTR0.WORD = 0x0003; //CMT0,CMT1 Start counting

540 :

541 : // MTU3_3 MTU3_4 PWM mode synchronized by RESET

542 : MSTP_MTU = 0; //Release module stop state

543 : MTU.TSTRA.BYTE = 0x00; //MTU Stop counting

544 :

545 : MTU3.TCR.BYTE = 0x23; //ILCK/64(651.04ns)

546 : MTU3.TCNT = MTU4.TCNT = 0; //MTU3,MTU4TCNT clear

547 : MTU3.TGRA = MTU3.TGRC = PWM_CYCLE; //cycle(16ms)

548 : MTU3.TGRB = MTU3.TGRD = SERVO_CENTER; //PWM(servo motor)

549 : MTU4.TGRA = MTU4.TGRC = 0; //PWM(left motor)

550 : MTU4.TGRB = MTU4.TGRD = 0; //PWM(right motor)

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551 : MTU.TOCR1A.BYTE = 0x40; //Selection of output level

552 : MTU3.TMDR.BYTE = 0x38; //TGRC,TGRD buffer function

553 : //PWM mode synchronized by RESET

554 : MTU4.TMDR.BYTE = 0x00; //Set 0 to exclude MTU3 effects

555 : MTU.TOERA.BYTE = 0xc7; //MTU3TGRB,MTU4TGRA,MTU4TGRB permission for output

556 :

557 : MTU.TSTRA.BYTE = 0x40; //MTU0,MTU3 count function

558 : }

559 :

560 : /***********************************************************************/

561 : /* Interrupt */

562 : /***********************************************************************/

563 : #pragma interrupt Excep_CMT0_CMI0(vect=28)

564 : void Excep_CMT0_CMI0(void)

565 : {

566 : cnt0++;

567 : cnt1++;

568 : }

569 :

570 : /***********************************************************************/

571 : /* Timer unit */

572 : /* Arguments: timer value, 1 = 1 ms */

573 : /***********************************************************************/

574 : void timer( unsigned long timer_set )

575 : {

576 : cnt0 = 0;

577 : while( cnt0 < timer_set );

578 : }

579 :

580 : /***********************************************************************/

581 : /* Sensor state detection */

582 : /* Arguments: masked values */

583 : /* Return values: sensor value */

584 : /***********************************************************************/

585 : unsigned char sensor_inp( unsigned char mask )

586 : {

587 : unsigned char sensor;

588 :

589 : sensor = ~PORT4.PORT.BYTE;

590 :

591 : sensor &= mask;

592 :

593 : return sensor;

594 : }

595 :

596 : /***********************************************************************/

597 : /* Read start bar detection sensor */

598 : /* Return values: Sensor value, ON (bar present):1, */

599 : /* OFF (no bar present):0 */

600 : /***********************************************************************/

601 : unsigned char startbar_get( void )

602 : {

603 : unsigned char b;

604 :

605 : b = ~PORT4.PORT.BIT.B0 & 0x01; /* Read start bar signal */

606 :

607 : return b;

608 : }

609 :

610 : /***********************************************************************/

611 : /* Cross line detection processing */

612 : /* Return values: 0: no cross line, 1: cross line */

613 : /***********************************************************************/

614 : int check_crossline( void )

615 : {

616 : unsigned char b;

617 : int ret;

618 :

619 : ret = 0;

620 : b = sensor_inp(MASK3_3);

621 : if( b==0xe7 ) {

622 : ret = 1;

623 : }

624 : return ret;

625 : }

626 :

627 : /***********************************************************************/

628 : /* Right half line detection processing */

629 : /* Return values: 0: not detected, 1: detected */

630 : /***********************************************************************/

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631 : int check_rightline( void )

632 : {

633 : unsigned char b;

634 : int ret;

635 :

636 : ret = 0;

637 : b = sensor_inp(MASK4_4);

638 : if( b==0x1f ) {

639 : ret = 1;

640 : }

641 : return ret;

642 : }

643 :

644 : /***********************************************************************/

645 : /* Left half line detection processing */

646 : /* Return values: 0: not detected, 1: detected */

647 : /***********************************************************************/

648 : int check_leftline( void )

649 : {

650 : unsigned char b;

651 : int ret;

652 :

653 : ret = 0;

654 : b = sensor_inp(MASK4_4);

655 : if( b==0xf8 ) {

656 : ret = 1;

657 : }

658 : return ret;

659 : }

660 :

661 : /***********************************************************************/

662 : /* DIP switch value read */

663 : /* Return values: Switch value, 0 to 15 */

664 : /***********************************************************************/

665 : unsigned char dipsw_get( void )

666 : {

667 : unsigned char sw,d0,d1,d2,d3;

668 :

669 : d0 = ( PORT6.PORT.BIT.B3 & 0x01 ); /* P63~P60 read */

670 : d1 = ( PORT6.PORT.BIT.B2 & 0x01 ) << 1;

671 : d2 = ( PORT6.PORT.BIT.B1 & 0x01 ) << 2;

672 : d3 = ( PORT6.PORT.BIT.B0 & 0x01 ) << 3;

673 : sw = d0 | d1 | d2 | d3;

674 :

675 : return sw;

676 : }

677 :

678 : /***********************************************************************/

679 : /* Push-button in MCU board value read */

680 : /* Return values: Switch value, ON: 1, OFF: 0 */

681 : /***********************************************************************/

682 : unsigned char buttonsw_get( void )

683 : {

684 : unsigned char sw;

685 :

686 : sw = ~PORTE.PORT.BIT.B5 & 0x01; /* Read ports with switches */

687 :

688 : return sw;

689 : }

690 :

691 : /***********************************************************************/

692 : /* Push-button in motor drive board value read */

693 : /* Return values: Switch value, ON: 1, OFF: 0 */

694 : /***********************************************************************/

695 : unsigned char pushsw_get( void )

696 : {

697 : unsigned char sw;

698 :

699 : sw = ~PORT7.PORT.BIT.B0 & 0x01; /* Read ports with switches */

700 :

701 : return sw;

702 : }

703 :

704 : /***********************************************************************/

705 : /* LED control in MCU board */

706 : /* Arguments: Switch value, LED0: bit 0, LED1: bit 1. 0: dark, 1: lit */

707 : /* */

708 : /***********************************************************************/

709 : void led_out_m( unsigned char led )

710 : {

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711 : led = ~led;

712 : PORTA.DR.BYTE = led & 0x0f;

713 : }

714 :

715 : /***********************************************************************/

716 : /* LED control in motor drive board */

717 : /* Arguments: Switch value, LED0: bit 0, LED1: bit 1. 0: dark, 1: lit */

718 : /* Example: 0x3 -> LED1: ON, LED0: ON, 0x2 -> LED1: ON, LED0: OFF */

719 : /***********************************************************************/

720 : void led_out( unsigned char led )

721 : {

722 : led = ~led;

723 : PORT7.DR.BIT.B6 = led & 0x01;

724 : PORT1.DR.BIT.B0 = ( led >> 1 ) & 0x01;

725 : }

726 :

727 : /***********************************************************************/

728 : /* Motor speed control */

729 : /* Arguments: Left motor: -100 to 100, Right motor: -100 to 100 */

730 : /* Here, 0 is stopped, 100 is forward, and -100 is reverse. */

731 : /* Return value: None */

732 : /***********************************************************************/

733 : void motor( int accele_l, int accele_r )

734 : {

735 : int sw_data;

736 :

737 : sw_data = dipsw_get() + 5;

738 : accele_l = accele_l * sw_data / 20;

739 : accele_r = accele_r * sw_data / 20;

740 :

741 : /* Left Motor Control */

742 : if( accele_l >= 0 ) {

743 : PORT7.DR.BYTE &= 0xef;

744 : MTU4.TGRC = (long)( PWM_CYCLE - 1 ) * accele_l / 100;

745 : } else {

746 : PORT7.DR.BYTE |= 0x10;

747 : MTU4.TGRC = (long)( PWM_CYCLE - 1 ) * ( -accele_l ) / 100;

748 : }

749 :

750 : /* Right Motor Control */

751 : if( accele_r >= 0 ) {

752 : PORT7.DR.BYTE &= 0xdf;

753 : MTU4.TGRD = (long)( PWM_CYCLE - 1 ) * accele_r / 100;

754 : } else {

755 : PORT7.DR.BYTE |= 0x20;

756 : MTU4.TGRD = (long)( PWM_CYCLE - 1 ) * ( -accele_r ) / 100;

757 : }

758 : }

759 :

760 : /***********************************************************************/

761 : /* Servo steering operation */

762 : /* Arguments: servo operation angle: -90 to 90 */

763 : /* -90: 90-degree turn to left, 0: straight, */

764 : /* 90: 90-degree turn to right */

765 : /***********************************************************************/

766 : void handle( int angle )

767 : {

768 : /* When the servo move from left to right in reverse, replace "-" with "+". */

769 : MTU3.TGRD = SERVO_CENTER - angle * HANDLE_STEP;

770 : }

771 :

772 : /***********************************************************************/

773 : /* end of file */

774 : /***********************************************************************/

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5.2. Differences between programs for kit07_rx62t.c and kit12_rx62t.c

The points of difference between kit07_rx62t.c and kit12_rx62t.c, are listed in the table below.

kit07_rx62t.c

(for use Sensor Board Ver.4)

kit12_rx62t.c

(for use Sensor Board Ver.5)

sensor_inp

function

unsigned char sensor_inp(

unsigned char mask )

{

unsigned char sensor;

sensor = ~PORT4.PORT.BYTE;

sensor &= 0xef;

if( sensor & 0x08 ) sensor |= 0x10;

sensor &= mask;

return sensor;

}

unsigned char sensor_inp(

unsigned char mask )

{

unsigned char sensor;

sensor = ~PORT4.PORT.BYTE;

// delete this line

sensor &= mask;

return sensor;

}

startbar_get

function

unsigned char startbar_get( void )

{

unsigned char b;

b = ~PORT4.PORT.BIT.B4 & 0x01;

return b;

}

unsigned char startbar_get( void )

{

unsigned char b;

b = ~ PORT4.PORT.BIT.B0 & 0x01;

return b;

}

5.3. On-Chip Peripheral Functions of RX62T MCU Used by the Program

The on-chip peripheral modules used for control on the RMC-RX62T board (RX62T MCU) included in the

MCU Car Rally Kit, Ver. 5.1, are listed below.

Items

On-Chip Peripheral Module of RMC-RX62T used to Control MCU Car

Generating interrupts at

1 ms intervals 1ms

CMT

Control of left motor,

right motor, and servo

Reset-synchronized PWM mode using MTU3

Rotary encoder*

(pulse count)

MTU0

Note: * These are not covered in Program Explanation Manual (this manual).

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5.4. Program Explanation

5.4.1. Start

1 : /***********************************************************************/

2 : /* Supported Microcontroller:RX62T */

3 : /* File: kit12_rx62t.c */

4 : /* File Contents: MCU Car Trace Basic Program(RX62T version) */

5 : /* Version number: Ver.1.00 */

6 : /* Date: 2013.09.01 */

7 : /* Copyright: Renesas Micom Car Rally Secretariat */

8 : /***********************************************************************/

First comes the comments section. The beginning of a comment is designated by /* and the end of a comment by

*/. All characters from the beginning to the end of a comment are ignored by the compiler. Comment lines are

used to include notes about the program.

5.4.2. Including External Files

16 : /*======================================*/

17 : /* Include */

18 : /*======================================*/

19 : #include "iodefine.h"

The #include statement is used to include (call) an external file.

File Name

Description

iodefine.h

This file defines registers used to control the on-chip peripheral functions of RX62T.

5.4.3. Symbol Definitions

21 : /*======================================*/

22 : /* Symbol definitions */

23 : /*======================================*/

24 :

25 : /* Constant settings */

26 : #define PWM_CYCLE 24575 /* Motor PWM period (16ms) */

27 : #define SERVO_CENTER 2300 /* Servo center value */

28 : #define HANDLE_STEP 13 /* 1 degree value */

29 :

30 : /* Masked value settings X:masked (disabled) O:not masked (enabled) */

31 : #define MASK2_2 0x66 /* X O O X X O O X */

32 : #define MASK2_0 0x60 /* X O O X X X X X */

33 : #define MASK0_2 0x06 /* X X X X X O O X */

34 : #define MASK3_3 0xe7 /* O O O X X O O O */

35 : #define MASK0_3 0x07 /* X X X X X O O O */

36 : #define MASK3_0 0xe0 /* O O O X X X X X */

37 : #define MASK4_0 0xf0 /* O O O O X X X X */

38 : #define MASK0_4 0x0f /* X X X X O O O O */

39 : #define MASK4_4 0xff /* O O O O O O O O */

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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PWM_CYCLE

PWM_CYCLE sets the PWM cycle for the signals applied to the right motor, left motor,

and servo. Here it is set to a PWM cycle of 16 ms. The value is calculated as follows:

PWM_CYCLE = desired PWM cycle / MTU3_3 timer general register C (MTU3.TGRC) count

source – 1

=16 ms / 651.04 ns – 1

= (16  10–3) / (651.04  10–9) – 1

= 24576 – 1 = 24575

For a detailed explanation, see the discussion of reset-synchronized PWM mode.

SERVO_CENTER

SERVO_CENTER sets the value at which the servo angle is 0 degrees (pointing straight

ahead). A standard servo will point forward when a 1.5 [ms] pulse width is applied.

Therefore, the pulse on width is set at 1.5 ms. The SERVO_CENTER setting value is

calculated as follows:

SERVO_CENTER = pulse on width / MTU3_3 timer general register C (MTU3.TGRC)

count source select bit setting – 1

= 1.5 ms /651.04 ns – 1

= (1.5 × 10-3) / (651.04 × 10–9) – 1

= 2304

Calculated servo centre is 2304.

In this sample program, 2300 is used for servo centre.

However, the actual servo centre value is slightly different for

every MCU car because of factors such as variation among

individual servos and the way the grooves in the holes in the

servo horn match up. This is analogous to the way that

everyone’s fingerprints are different. For this reason, this value

needs to be changed for each MCU car to adjust the servo

angle such that the car runs in a straight line when the

software specifies a turning angle of 0 degrees.

▲Servo horn

HANDLE_STEP

HANDLE_STEP sets a value equivalent to 1 degree of servo movement. A 0.7 ms PWM on

width causes the servo to turn 90 degrees to the left, and a 2.3 ms on width causes it to turn

90 degrees to the right. If we divide the difference between these two by 180, we can obtain

the value equivalent to 1 degree.

 On width of 90 degrees left

MTU3.TGRD + PWM waveform on width / MTU3_3 timer counter count source – 1

= (0.7 × 10–3) / (651.04 × 10–9) – 1

= 1075 – 1 = 1074

 On width of 90 degrees right

MTU3.TGRD + PWM waveform on width / MTU3_3 timer counter count source – 1

= (2.3 × 10–3) / (651.04 × 10–9) – 1

= 3532 – 1 = 3531

 Value equivalent to 1 degree

(Right – left) / 180 = (3531 – 1074) / 180 = 13.65  13

Therefore, the value of HANDLE_STEP is defined as 13. Change this value to adjust the

value equivalent to 1 degree of servo movement.

MASK2_2

MASK2_0

MASK0_2

MASK3_3

MASK0_3

MASK3_0

MASK4_0

MASK0_4

MASK4_4

The sensor_inp function defines common mask values used when masking sensor values.

These values are defined in the format MASK + A + _ (underscore) + B.

 A: Of the four sensors on the left, A sensors are valid (unmasked).

 B: Of the four sensors on the right, B sensors are valid (unmasked).

 The other sensors are masked.

For details, see 6.4.12, sensor_inp Function.

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5.4.4. Prototype Declarations

41 : /*======================================*/

42 : /* Prototype declarations */

43 : /*======================================*/

44 : void init(void);

45 : void timer( unsigned long timer_set );

46 : unsigned char sensor_inp( unsigned char mask );

47 : unsigned char startbar_get( void );

48 : int check_crossline( void );

49 : int check_rightline( void );

50 : int check_leftline( void );

51 : unsigned char dipsw_get( void );

52 : unsigned char buttonsw_get( void );

53 : unsigned char pushsw_get( void );

54 : void led_out_m( unsigned char led );

55 : void led_out( unsigned char led );

56 : void motor( int accele_l, int accele_r );

57 : void handle( int angle );

58 :

Prototype declarations must be made before functions are used to allow checking of the types and quantity of

arguments of the user-created functions. A semicolon (;) is appended after a function to indicate a function

prototype.

An example prototype declaration is shown below.

void motor( int accele_l, int accele_r ); /* Prototype declarations */

void main( void )

{

int a, b;

a = 50;

b = 100;

motor( a, b );  Check to confirm that the first and second arguments are of type int as specified in

the prototype declaration. If either argument is not type int, the compiler will

return an error.

}

/* Motor control function */

void motor( int accele_l, int accele_r )

{

Program

}

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5.4.5. Global Variable Declarations

59 : /*======================================*/

60 : /* Global variable declarations */

61 : /*======================================*/

62 : unsigned long cnt0;

63 : unsigned long cnt1;

64 : int pattern;

65 :

Global variables are defined separately from functions and may be referenced by any function. By means of

comparison, the usual type of variable, which is defined within a function, is called a local variable and may be

referenced only within that function.

An example prototype declaration is shown below.

void a( void ); /* Prototype declarations */

int timer; /* Global variable */

void main( void )

{

int i;

timer = 0;

i = 10;

printf(“%/n”,timer );  0 is displayed.

a();

printf(“%/n”,timer );  timer is a global variable,

so the value 20 set by function a is displayed.

printf(“%/n”,i );  Function a also uses variable i, but since it is a local variable,

} the value of variable i within function a is irrelevant.

The value of 10 set by this function is displayed.

void a( void )

{

int i;

i = 20;

timer = i;

}

The program kit12_rx62t.c contains three global variable declarations.

Variable name

Type

Usage

cnt0

unsigned long

This function increments the count value by 1 at 1 ms intervals.

Used by the timer function to count at 1 ms intervals.

The details are described in the section covering the timer function.

cnt1

unsigned long

This function increments the count value by 1 at 1 ms intervals.

This variable can be used freely by the program to measure duration. For

example, it can be used to “do ○○ if 300 ms has elapsed and do □□

otherwise.” The details are described in the section covering the main

function.

pattern

int

This is the pattern number. The details are described in the section

covering the main function.

Under the ANSI C standard (the C language standard), un-initialised data must have an initial value of

0x00. Therefore, these variables all have a value of 0.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.6. init Function(Clock Choice)

The init function initialises the on-chip peripheral functions of the RX62T MCU. The name init stands for

“initialise.” The init function initialises several on-chip peripheral functions. These are described below, broken

down by function.

The RX62T MCU board already has a 12.288MHz crystal oscillator.

So choose 98.304MHz (12.288 x 8) for system clock and 49.152MHz (12.288 x 4) for peripheral clock.

481 : /***********************************************************************/

482 : /* RX62T Initialization */

483 : /***********************************************************************/

484 : void init(void)

485 : {

486 : // System Clock

487 : SYSTEM.SCKCR.BIT.ICK = 0; //12.288*8=98.304MHz

488 : SYSTEM.SCKCR.BIT.PCK = 1; //12.288*4=49.152MHz

5.4.7. init Function (Port I/O Settings)

Next, the init function makes port I/O settings.

490 : // Port I/O Settings

491 : PORT1.DDR.BYTE = 0x03; //P10:LED2 in motor drive board

492 :

493 : PORT2.DR.BYTE = 0x08;

494 : PORT2.DDR.BYTE = 0x1b; //P24:SDCARD_CLK(o)

495 : //P23:SDCARD_DI(o)

496 : //P22:SDCARD_DO(i)

497 : //CN:P21-P20

498 : PORT3.DR.BYTE = 0x01;

499 : PORT3.DDR.BYTE = 0x0f; //CN:P33-P31

500 : //P30:SDCARD_CS(o)

501 : //PORT4:input //sensor input

502 : //PORT5:input

503 : //PORT6:input

504 :

505 : PORT7.DDR.BYTE = 0x7e; //P76:LED3 in motor drive board

506 : //P75:forward reverse signal(right motor)

507 : //P74:forward reverse signal(left motor)

508 : //P73:PWM(right motor)

509 : //P72:PWM(left motor)

510 : //P71:PWM(servo motor)

511 : //P70:Push-button in motor drive board

512 : PORT8.DDR.BYTE = 0x07; //CN:P82-P80

513 : PORT9.DDR.BYTE = 0x7f; //CN:P96-P90

514 : PORTA.DR.BYTE = 0x0f; //CN:PA5-PA4

515 : //PA3:LED3(o)

516 : //PA2:LED2(o)

517 : //PA1:LED1(o)

518 : //PA0:LED0(o)

519 : PORTA.DDR.BYTE = 0x3f; //CN:PA5-PA0

520 : PORTB.DDR.BYTE = 0xff; //CN:PB7-PB0

521 : PORTD.DDR.BYTE = 0x0f; //PD7:TRST#(i)

522 : //PD5:TDI(i)

523 : //PD4:TCK(i)

524 : //PD3:TDO(o)

525 : //CN:PD2-PD0

526 : PORTE.DDR.BYTE = 0x1b; //PE5:SW(i)

527 : //CN:PE4-PE0

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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Following table shows relationship between ports of RX62T and kit car.

Port

bit7

bit6

bit5

bit4

bit3

bit2

bit1

bit0

1

Not connected

LED2 in motor

drive board

output

2

SDCARD_CLK

SDCARD_DI

SDCARD_DO

Not connected

3

Not connected

SDCARD_CS

4

Sensor board

course state

input

Sensor board

course state

input

Sensor board

course state

input

Sensor board

start bar state

input

Sensor board

course state

input

Sensor board

course state

input

Sensor board

course state

input

Sensor board

course state

input

5

Not connected

6

Not connected

7

LED3 in

motor drive

board /output

forward reverse

signal

(right motor)

forward reverse

signal

(left motor)

PWM

(right motor)

PWM

(left motor)

PWM

(servo motor)

Push-button in

motor drive

board

8

Not connected

9

Not connected

A

Not connected

LED3 in

MCU board

output

LED2 in

MCU board

output

LED1 in

MCU board

output

LED0 in

MCU board

output

B

Not connected

D

TRST#

TMS

TDI

TCK

TDO

Not connected

E

Push-button

in MCU board

input

Not connected

 Bits that are crossed out in the table have no pins associated with them.

 All ports become input ports after a reset.

 Port4,5,6 and bit2 of portE are input only.

According to following rules, every ports are set by PnDDR.( n=1 to 3,7 to 9,A,B,D and E)

[1] Pins on which signals are output are set to 1.

[2] Pins on which signals are input are set to 0.

[3] Unconnected pins should either be connected to a pull-up or pull-down resistor and set to input mode (0) or

left open (not connected to anything) and set to output mode (1). Here, the latter setting is used.

[4] Bits with no associated pins (crossed out in the table) are set to 0.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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Based on rules [1] to [4], the table can be rewritten with 1s and 0s as follows:

Port

bit7

bit6

bit5

bit4

bit3

bit2

bit1

bit0

Hexadecimal

1

0

1

0x03

2

0

1

0

1

0x1b

3

0

1

0x0f

7

0

1

0

0x7e

8

0

1

0x07

9

0

1

0x7f

A

0

1

0x3f

B

1

0xff

D

0

1

0x0f

E

0

1

0

1

0x1b

In the C language numeric values cannot be expressed in binary notation, so they must be converted to decimal or

hexadecimal format. The conversion is generally from binary to hexadecimal format, since that is easier than

converting to decimal format.

From above table, value of Direction Register set as follows.

Port

Direction Register

Setting value

1

PORT1.DDR.BYTE

0x03

2

PORT2.DDR.BYTE

0x1b

3

PORT3.DDR.BYTE

0x0f

7

PORT7.DDR.BYTE

0x7e

8

PORT8.DDR.BYTE

0x07

9

PORT9.DDR.BYTE

0x7f

A

PORTA.DDR.BYTE

0x3f

B

PORTB.DDR.BYTE

0xff

D

PORTD.DDR.BYTE

0x0f

E

PORTE.DDR.BYTE

0x1b

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.8. init Function (Compare Match Timer Settings)

CMT0 is used to generate an interrupt at 1 ms intervals.

529 : // Compare match timer

530 : MSTP_CMT0 = 0; //CMT Release module stop state

531 : MSTP_CMT2 = 0; //CMT Release module stop state

532 :

533 : ICU.IPR[0x04].BYTE = 0x0f; //CMT0_CMI0 Priority of interrupts

534 : ICU.IER[0x03].BIT.IEN4 = 1; //CMT0_CMI0 Permission for interrupt

535 : CMT.CMSTR0.WORD = 0x0000; //CMT0,CMT1 Stop counting

536 : CMT0.CMCR.WORD = 0x00C3; //PCLK/512

537 : CMT0.CMCNT = 0;

538 : CMT0.CMCOR = 96; //1ms/(1/(49.152MHz/512))

539 : CMT.CMSTR0.WORD = 0x0003; //CMT0,CMT1 Start counting

Line 530

to

Line 531

According to the state of the module stop function, the compare match timer will be set to permitted

or prohibited. At the initial state, the compare match timer is set to prohibited. So change it to

permitted.

Line 533

Sets priority of interrupts. In this program, maximum level (level 15) is set.

Line 534

Permission for interrupt request to CPU.

Line 535

Sets timer counting function to stop.

Line 536

Choose clock for counting up. In this program, PCLK/512 is chosen.

1/(49.152MHz /512) = 10.42 us

Line 537

Initialises counter to zero.

Line 538

Sets cycle of compare match. To generate interruptｓ every ms, set the value of CMT0.CMCOR as

96.

CMT0.CMCOR = cycle(1ms)/ counting clock(10.42 us)

CMT0.CMCOR = (1×10-3)/(10.42×10-6)

CMT0.CMCOR = 95.97

Set CMT0.CMCOR = 96.

Line 539

Sets timer counting function to start.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.9. init Function (Multi-Function Timer Pulse Unit 3 Settings)

MTU3_3 and MTU3_4 are used in reset-synchronized PWM mode to output PWM signals to the left motor, right

motor, and servo.

541 : // MTU3_3 MTU3_4 PWM mode synchronized by RESET

542 : MSTP_MTU = 0; //Release module stop state

543 : MTU.TSTRA.BYTE = 0x00; //MTU Stop counting

544 :

545 : MTU3.TCR.BYTE = 0x23; //ILCK/64(651.04ns)

546 : MTU3.TCNT = MTU4.TCNT = 0; //MTU3,MTU4TCNT clear

547 : MTU3.TGRA = MTU3.TGRC = PWM_CYCLE; //cycle(16ms)

548 : MTU3.TGRB = MTU3.TGRD = SERVO_CENTER; //PWM(servo motor)

549 : MTU4.TGRA = MTU4.TGRC = 0; //PWM(left motor)

550 : MTU4.TGRB = MTU4.TGRD = 0; //PWM(right motor)

551 : MTU.TOCR1A.BYTE = 0x40; //Selection of output level

552 : MTU3.TMDR.BYTE = 0x38; //TGRC,TGRD buffer function

553 : //PWM mode synchronized by RESET

554 : MTU4.TMDR.BYTE = 0x00; //Set 0 to exclude MTU3 effects

555 : MTU.TOERA.BYTE = 0xc7; //MTU3TGRB,MTU4TGRA,MTU4TGRB permission

for output

556 :

557 : MTU.TSTRA.BYTE = 0x40; //MTU0,MTU3 count function

558 : }

The output settings for reset-synchronized PWM mode in the present case are shown at right below.

Reset-synchronized

PWM mode

MTIOC3A pin (P33)

MTIOC3B pin (P71)

MTIOC3D pin (P74)

MTIOC4A pin (P72)

MTIOC4C pin (P75)

MTIOC4B pin (P73)

MTIOC4D pin (P76)

Forward phase

Reverse phase

Forward phase

Reverse phase

Forward phase

Reverse phase

MTU3_3

MTU3_4

Reset-synchronized PWM mode output settings in present case

Reset-synchronized

PWM mode

MTIOC3B pin (P71)

MTIOC4A pin (P72)

MTIOC4B pin (P73)

Forward phase

All PWM signals output in reset-synchronized PWM mode

To servo motor



To left motor



To right motor



MTU3_3

MTU3_4

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.10. Excep_CMT0_CMI0 Function (Interrupt Every 1 ms)

The Excep_CMT0_CMI0 function is set by Compare Match Timer to run once every 1 ms.

560 : /***********************************************************************/

561 : /* Interrupt */

562 : /***********************************************************************/

563 : #pragma interrupt Excep_CMT0_CMI0(vect=28)

564 : void Excep_CMT0_CMI0(void)

565 : {

566 : cnt0++;

567 : cnt1++;

568 : }

Line 563

This syntax of this line is:

#pragma interrupt interrupt handler function name (vect = software interrupt number)

So whenever the interrupt designated by software interrupt number occurs, interrupt handler function

name is executed. From the software interrupt table we can see that the Compare Match Timer

interrupt is designated as number 28. The source code uses #pragma interrupt to specify that the

Excep_CMT0_CMI0 function is run when interrupt number 28 occurs.

Line 564

This is the function triggered by the Compare Match Timer interrupt. It is not possible to specify

arguments or return values for an interrupt function. Therefore, the syntax void function name

( void ) must be used.

Line 566

Increments (+1) variable cnt0. The function is executed at 1 ms intervals, so the value of variable

cnt0 increases by 1 every 1 ms.

Line 567

Increments (+1) variable cnt1. The function is executed at 1 ms intervals, so the value of variable

cnt1 increases by 1 every 1 ms.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.11. timer Function (Pause)

The timer function is used to pause operation.

570 : /***********************************************************************/

571 : /* Timer unit */

572 : /* Arguments: timer value, 1 = 1 ms */

573 : /***********************************************************************/

574 : void timer( unsigned long timer_set )

575 : {

576 : cnt0 = 0;

577 : while( cnt0 < timer_set );

578 : }

(1) Using the timer Function

The usage of the timer function is illustrated below.

timer( desired pause duration );

The argument specifies the pause duration in milliseconds. An example is shown below.

motor( 50, 100 );  Several 100 s

timer( 1000 ); 1000 ms

Following motor control, the timer function pauses operation for 1,000 ms.

(2) Program Explanation

The following explanation assumes that the function is executed as follows:

timer( 1000 );

Line 576

Clears cnt0 to 0.

Line 577

1.

First, the following statement is processed:

while( cnt0 < timer_set );

Variable cnt0 was cleared to 0 on line 576. Variable timer_set is an argument of the timer

function. The line is therefore equivalent to:

while( 0 < 1000 );

The condition within the parentheses is not satisfied, so processing of the statement repeats over

and over.

2.

After 1 ms elapses an Excep_CMT0_CMI0 interrupt occurs. Processing of the while statement

in the current line stops, and the following line in the interrupt handler is processed:

560 : cnt0++;  This is equivalent to 0++, therefore the value becomes 1.

The value of cnt0 is now 1. Processing of the interrupt handler ends, and control returns to the

line at which the interrupt occurs.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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Line 577

3.

Control returns to the line with the while statement:

while( 1 < 1000 );

The value of cnt0 is now 1 because it was incremented by the interrupt handler. Once again, the

condition within the parentheses is not satisfied, and processing of the statement repeats over

and over.

4.

When 2. has been processed 1,000 times, the value of cnt0 is 1,000.

while( 1000 < 1000 );

The condition of the while statement is satisfied. Processing of the while statement ends, and

processing continues to the next line. There is no next line in the function, so the timer function

ends. The Excep_CMT0_CMI0 function is executed every 1 ms when a Compare Match

Timer interrupt occurs. Processing the while statement repeatedly until the value of cnt0

reaches 1,000 means that the while statement repeats over a duration of 1,000 ms. In this way, a

specified duration of time can be measured by using the timer function to count the occurrences

of an interrupt, which is triggered at 1 ms intervals by Compare Match Timer.

5.4.12. sensor_inp Function (Read State of Sensors)

The sensor_inp function reads the state of the sensors on the sensor board.

580 : /***********************************************************************/

581 : /* Sensor state detection */

582 : /* Arguments: masked values */

583 : /* Return values: sensor value */

584 : /***********************************************************************/

585 : unsigned char sensor_inp( unsigned char mask )

586 : {

587 : unsigned char sensor;

588 :

589 : sensor = ~PORT4.PORT.BYTE;

590 :

591 : sensor &= mask;

592 :

593 : return sensor;

594 : }

Line 587

Specifies variable sensor as type unsigned char. This variable is used in the sensor_inp function to

process the states of the sensors. Sensor board data is read from port 4 with a bit width of 8 bits.

Therefore, variable sensor is specified as an unsigned 8-bit char.

Line 589

Reads the sensor board data from port 4. The output from the sensors is 0 for white and 1 for black,

which is confusing because it is the reverse of the human sense of sight. Therefore, a tilde (~) is used

to reverse the values so that 1 represents white and 0 represents black.

Line 591

Performs an AND operation on variable sensor, which contains the sensor data processed up to line

585, and the mask value used as an argument of the sensor_inp function. This forces the value of all

unneeded bits to 0.

Line 593

Returns variable sensor as a return value, ending the function.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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(1) Treatment of bit0

The rightmost sensor which detects the course and the sensor which detects the start bar of the Sensor Board Ver.5

are input in an OR connection to bit 0 terminal of port 0. This is shown below.

０００００１１０

Course sensor

７

０

１

２

３

５

６

４

B

W

B

Value of course sensor

０

６

Hexadecimal

０

Value of Start bar sensor

０

Start bar sensor

Course state

Result

０００００１１０

OR)

No start bar

Start bar state

It is unknown whether the start bar detection sensor reacted when bit 0 became “1” or whether bit 0 of the course

detection sensor reacted. But the two states shown in the table below cannot happen simultaneously.

State

Picture

Description

Before

start

It judges

bit0＝"1"： There is start bar

"0"： No start bar

because the rightmost sensor is surely

black if the Sensor Board is set over the

centre line.

After

start

It judges

bit0＝"1"：Rightmost course :white

"0"：Rightmost course : black

because there is no need to check the

reading of the start bar sensor after the

start.

Monitor of rightmost course sensor

Monitor of Start bar sensor

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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(3) Masking

Line 587 performs masking on the sensor data. Masking forces to 0 the value of the bits that do not require

checking. It is accomplished by using an AND operation.

(a) Why Is Masking Necessary?

Since each port comprises 8 bits, it is not possible to check bits singly. (Actually, it is possible if we use a

method called a bit field, but we will not deal with that here.) Instead, all 8 bits are checked at the same time.

For example, if we want to determine whether or not the value of the bit corresponding to the leftmost sensor is 1,

you might think we could use the following code:

if( Sensor value == 0x80 ) {

/* Run this code if value of bit 7 is 1 */

}

But we don’t know the values of bits 6 to 0. If, for example, the values of both bit 7 and bit 0 are 1, the result

would be as follows:

if(Sensor value 0x81 == 0x80 ) {  Sensor value =1000 0001=0x81

/* Run this code if value of bit 7 is 1 */

}

The value of bit 7 is 1, but since the value of bit 0 is also 1 the sensor value is determined not to be 0x80 and the

code between the brackets is not executed. Proper checking is not possible in this case. This is why we need

masking.

117B(b) What Masking Does

The above method does not enable us to perform proper checking because we do not know if the values of the bits

other than 7 are 0 or 1. Masking lets us force the values of bits 6 to 0 to 0.

Since we know the values of bits 6 to 0 must be 0, we can check the sensor value based on this assumption. For

example, we can check whether or not the value of bit 7 is 1 as follows:

if(sensor value with bit 7 unchanged and bits 6 to 0 cleared to 0 =0x80 ) {

/* Run this code if value of bit 7 is 1 */

}

Now it is possible to determine whether the value of bit 7 is 0 or 1, and if it is 1 the code between the brackets is

executed.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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(c) Determining Masking Values and Performing Masking

In software we can use a logic operation known as the logical product, which is also called an AND operation. For

example, if the state of the sensors is BBBWWWWW, the sensor value will be 00011111. When checking bit 7

there is no need to check bits 6 to 0.

Bit

7

6

5

4

3

2

1

0

Necessary

Unnecessary

To clear the unnecessary bits to 0, we set the mask value for those bits to 0 and perform an AND operation.

Consequently, in the mask value the unnecessary bits should be cleared to 0 and the necessary bits set to 1.

Bit

7

6

5

4

3

2

1

0

Mask

value

１

０

We perform an AND operation on the sensor value and mask value, and then check the result against the bits to be

checked (see figure below).

○○○○○●●●

1 1 1 1 1 0 0 0

Mask value

Sensor value

1 1 1 1 1 0 0 0

1 0 0 0 0 0 0 0

)AND

1 0 0 0 0 0 0 0

Result

Return value

Sensor state

This can be converted into the following lines of code:

if( (Sensor value & 0x80) == 0x80 ) {

/* Run this code if value of bit 7 is 1 */

}

We know that bits 6 to 0 have all been forcibly cleared to 0 by masking, so we can assume the value of bits 6 to 0

is 0 when making the comparison.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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(d) Structure of sensor_inp Function

The sensor_inp function obtains sensor data and performs masking. Masking, the last step in processing the

sensor value, is performed after the sensor value is processed by inversion, bit copying, etc.

580 : /***********************************************************************/

581 : /* Sensor state detection */

582 : /* Arguments: masked values */

583 : /* Return values: sensor value */

584 : /***********************************************************************/

585 : unsigned char sensor_inp( unsigned char mask )

586 : {

587 : unsigned char sensor;

588 :

589 : sensor = ~PORT4.PORT.BYTE;

590 :

591 : sensor &= mask;

592 :

593 : return sensor;

594 : }

(e) Mask Value Definition

In kit12_rx62t.c the most commonly used mask values are predefined using define. This is performed in lines 31

to 39 of the source code. The format used for these definitions is as follows:

#define MASKA_B Mask value

Mask values are defined using the rule MASK + A + _ (underscore) + B. The meanings of these elements are as

follows:

 A: Of the four sensors on the left, A sensors are valid (unmasked).

 B: Of the four sensors on the right, B sensors are valid (unmasked).

 The other sensors are masked.

The definitions used in the program are listed in the following table:

Defined Mask

Character String

Mask

Value

Binary

Description

MASK2_2

0x66

0110 0110

The two middle sensors on the left and the two middle

sensors on the right are valid (unmasked), and the

others are masked.

MASK2_0

0x60

0110 0000

The two middle sensors on the left are valid

(unmasked), and the others are masked.

MASK0_2

0x06

0000 0110

The two middle sensors on the right are valid

(unmasked), and the others are masked.

MASK3_3

0xe7

1110 0111

The three sensors on the left and the three sensors on

the right are valid (unmasked), and the others are

masked.

MASK0_3

0x07

0000 0111

The three sensors on the right are valid (unmasked),

and the others are masked.

MASK3_0

0xe0

1110 0000

The three sensors on the left are valid (unmasked), and

the others are masked.

MASK4_0

0xf0

1111 0000

The four sensors on the left are valid (unmasked), and

the others are masked.

Masking is the last step in

processing the sensor value.

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MASK0_4

0x0f

0000 1111

The four sensors on the right are valid (unmasked), and

the others are masked.

MASK4_4

0xff

1111 1111

Four sensors on the right and four sensors on the left

are valid (unmasked), and the others are masked.

Note: The result of MASK4_4 is that all of the

sensors are valid (unmasked). This pattern

is provided because the parentheses of

the sensor_inp function must contain a

value. When masking is not necessary,

using MASK4_4 results in a mask value

of 0xff: all sensors valid (unmasked).

The mask value specified between the parentheses of the sensor_inp function can be set by using one of the mask

character strings described above.

If none of the provided mask character strings correspond to your desired mask values, add additional definitions

of your own. Alternately, you can specify the mask value directly as a numeric value, without using a mask

character string.

(4) Using the sensor_inp Function

if( sensor_inp( Mask value ) == Sensor check value) {

Run this code if the expression is true.

} else {

Run this code if the expression is not true.

}

In the sensor_inp function, mask value contains the value used when applying masking to the sensor value, and

sensor check value contains the value after masking is applied that is used for checking. For example, the process

is as follows when the sensor value is 0x1f, the mask value is MASK0_2, and the sensor check value is 0x04:

if( sensor_inp( MASK0_2 ) == 0x04 ) {

Run this code if the expression is true.

} else {

Run this code if the expression is not true.

}

1.

The sensor value is 0001 1111 and the mask value of the sensor_inp function is 0000 0110. The result of

the AND operation is as follows:

Sensor value 0001 1111

Mask value 0000 0110 (AND

Result 0000 0110 0x06 after conversion to hexadecimal

2.

The result 0x06 and sensor check value 0x04 are compared. Since they do not match, the lines represented

by “Run this code if the expression is not true” are processed.

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(5) Notes

We have explained above how the sensor_inp function uses the same value for bits 4 and 3. However, depending

on the mask value, the values of bits 4 and 3 may differ in the return value of the sensor_inp function. When

writing program code, also pay attention to the mask value of the sensor_inp function.

if( sensor_inp(MASK4_4) == 0x1f ) { ●●●○○○○○ Possible

}

if( sensor_inp(MASK4_4) == 0x07 ) { ●●●●●○○○ Possible

}

if( sensor_inp(MASK4_4) == 0x0f ) { ●●●●○○○○ 0x0f not possible

}

if( sensor_inp(MASK4_4) == 0xf8 ) { ○○○○○●●● Possible

}

if( sensor_inp(MASK4_4) == 0xe0 ) { ○○○●●●●● Possible

}

if( sensor_inp(MASK4_4) == 0xf0 ) { ○○○○●●●● 0xf0 not possible

}

if( sensor_inp(MASK0_4) == 0x0f ) { ××××○○○○ 0x0f possible depending

on mask value!

}

if( sensor_inp(MASK4_0) == 0xf0 ) { ○○○○×××× 0xf0 possible depending

on mask value!

}

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5.4.13. check_crossline Function (Crossline Detection)

There are two white lines on the track 500 mm to 1,000 mm before a crank. These are called cross lines. The

check_cross line function detects these cross lines.

The return value is 1 when a cross line is detected and 0 when no cross line is detected.

610 : /***********************************************************************/

611 : /* Cross line detection processing */

612 : /* Return values: 0: no cross line, 1: cross line */

613 : /***********************************************************************/

614 : int check_crossline( void )

615 : {

616 : unsigned char b;

617 : int ret;

618 :

619 : ret = 0;

620 : b = sensor_inp(MASK3_3);

621 : if( b==0xe7 ) {

622 : ret = 1;

623 : }

624 : return ret;

625 : }

Line 619

This initialises the variable ret, which stores the return value. A value of 1 is stored in variable ret

when a cross line is detected and 0 when no cross line is detected. For the time being we do not know

which is correct, so we insert a value of 0, no cross line detected.

Line 620

This reads the sensors and stores the result in variable b. The sensor mask value is MASK3_3 (0xe7),

so a total of six sensors are read, three on the right and three on the left.

The sensors that are read are illustrated below:

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Line 621

This checks whether or not the sensor state is 0xe7. A cross line is detected when the sensor value is

0xe7. This is illustrated below:

The if condition is met when the sensor value is 0xe7, and variable ret is set to 1. If the value is

something else, the condition is not met and the value of variable ret remains unchanged at 0.

Variable ret is the return value, so a value of 1 means “cross line detected” and a value of 0 means

“no cross line detected.”

Cross line

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.14. check_rightline function (Right Half Line Detection)

There are two right half lines on the track 500 mm to 1,000 mm before a right lane change. The check_rightline

function detects the right half lines.

The return value is 1 when a right half line is detected and 0 when no right half line is detected.

627 : /***********************************************************************/

628 : /* Right half line detection processing */

629 : /* Return values: 0: not detected, 1: detected */

630 : /***********************************************************************/

631 : int check_rightline( void )

632 : {

633 : unsigned char b;

634 : int ret;

635 :

636 : ret = 0;

637 : b = sensor_inp(MASK4_4);

638 : if( b==0x1f ) {

639 : ret = 1;

640 : }

641 : return ret;

642 : }

Line 636

This initialises the variable ret, which stores the return value. A value of 1 is stored in this variable

when a right half line is detected and 0 when no right half line is detected. For the time being we do

not know which is correct, so we insert a value of 0, no right half line detected.

Lines

637 and

638

This checks the sensor state. The mask value is MASK4_4, so all the sensors are read. A right half

line is detected when the sensor value is 0x1f. This is illustrated below:

The if condition is met when the sensor value is 0x1f, and variable ret is set to 1. If the value is

something else, the condition is not met and the value of variable ret remains unchanged at 0.

Variable ret is the return value, so a value of 1 means “right half line detected” and a value of 0 means

“no right half line detected.”

Half line

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.15. check_leftline function (Left Half Line Detection)

There are two left half lines on the track 500 mm to 1,000 mm before a left lane change. The check_leftline

function detects the left half lines.

The return value is 1 when a left half line is detected and 0 when no left half line is detected.

644 : /***********************************************************************/

645 : /* Left half line detection processing */

646 : /* Return values: 0: not detected, 1: detected */

647 : /***********************************************************************/

648 : int check_leftline( void )

649 : {

650 : unsigned char b;

651 : int ret;

652 :

653 : ret = 0;

654 : b = sensor_inp(MASK4_4);

655 : if( b==0xf8 ) {

656 : ret = 1;

657 : }

658 : return ret;

659 : }

Line 653

This initialises the variable ret, which stores the return value. A value of 1 is stored in this variable

when a left half line is detected and 0 when no left half line is detected. For the time being we do not

know which is correct, so we insert a value of 0, no left half line detected.

Lines

654 and

655

This checks the sensor state. The mask value is MASK4_4, so all the sensors are read. A left half line

is detected when the sensor value is 0xf8. This is illustrated below:

The if condition is met when the sensor value is 0xf8, and variable ret is set to 1. If the value is

something else, the condition is not met and the value of variable ret remains unchanged at 0.

Variable ret is the return value, so a value of 1 means “left half line detected” and a value of 0 means

“no left half line detected.”

Half line

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.16. dipsw_get Function (Reading DIP Switches)

The dipsw_get function reads the state of the DIP switches on the RMC-RX62T board.

The return value is a value between 0 and 15, according to the DIP switch value.

661 : /***********************************************************************/

662 : /* DIP switch value read */

663 : /* Return values: Switch value, 0 to 15 */

664 : /***********************************************************************/

665 : unsigned char dipsw_get( void )

666 : {

667 : unsigned char sw,d0,d1,d2,d3;

668 :

669 : d0 = ( PORT6.PORT.BIT.B3 & 0x01 ); /* P63~P60 read */

670 : d1 = ( PORT6.PORT.BIT.B2 & 0x01 ) << 1;

671 : d2 = ( PORT6.PORT.BIT.B1 & 0x01 ) << 2;

672 : d3 = ( PORT6.PORT.BIT.B0 & 0x01 ) << 3;

673 : sw = d0 | d1 | d2 | d3;

674 :

675 : return sw;

676 : }

A 4-bit DIP switch used on the RMC-RX62T MCU board is connected to Port 6. Switch #1 of this DIP switch is

connected to bit 3 of Port 6. Similarly, switch #4 is connected to bit 0 of Port 6.

The operation of the dipsw_get function when the DIP switch setting is 1010 (ON, OFF, ON, OFF) is illustrated

below.

3

2

1

0

Read

Result

1

0

1

0

1

0

P60

P61

P62

P63

0

1

0

1

0

MCU

0

1

2

3

4

5

6

7

 bit #

Value of bit #3 of Read is set to bit #0 of Result.

:

Value of bit #0 of Read is set to bit #3 of Result.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.17. buttonsw_get Function (Reading the Pushbutton State in MCU board)

The buttonsw_get function reads the state of the pushbutton on the MCU board.

The return value is 1 when the button is depressed and 0 when it is released.

678 : /***********************************************************************/

679 : /* Push-button in MCU board value read */

680 : /* Return values: Switch value, ON: 1, OFF: 0 */

681 : /***********************************************************************/

682 : unsigned char buttonsw_get( void )

683 : {

684 : unsigned char sw;

685 :

686 : sw = ~PORTE.PORT.BIT.B5 & 0x01; /* Read ports with switches */

687 :

688 : return sw;

689 : }

The pushbutton is connected to bit 5 of port E. The operation of the button_get function when the pushbutton is

depressed is illustrated below.

7

6

5

4

3

2

1

0

Read.

0

?

1

Result.

0

1

Line 686: Read port E.

Line 686: Invert.

Line 686: Apply 0x01

mask value.

ON

5

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5.4.18. pushsw_get Function (Reading the Pushbutton State)

The pushsw_get function reads the state of the pushbutton on the motor drive board.

The return value is 1 when the button is depressed and 0 when it is released.

691 : /***********************************************************************/

692 : /* Push-button in motor drive board value read */

693 : /* Return values: Switch value, ON: 1, OFF: 0 */

694 : /***********************************************************************/

695 : unsigned char pushsw_get( void )

696 : {

697 : unsigned char sw;

698 :

699 : sw = ~PORT7.PORT.BIT.B0 & 0x01; /* Read ports with switches */

700 :

701 : return sw;

702 : }

The pushbutton is connected to bit 0 of port 7. Bits 6 to 1 of port 7 do not interest us, so bit operations are used to

fetch the value of only the bit associated with the pushbutton.

The operation of the pushsw_get function when the pushbutton is depressed is illustrated below.

7

6

5

4

3

2

1

0

Read.

?

0

?

1

Result.

0

1

Line 699: Read port 7.

Line 699: Invert.

Line 699: Apply 0x01

mask value.

ON

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.19. startbar_get Function (Reading the Start Bar Detection Sensor)

The startbar_get function determines whether the start bar is present (closed) or not (open).

The return value is 1 when the start bar is present and 0 when it is not.

596 : /***********************************************************************/

597 : /* Read start bar detection sensor */

598 : /* Return values: Sensor value, ON (bar present):1, */

599 : /* OFF (no bar present):0 */

600 : /***********************************************************************/

601 : unsigned char startbar_get( void )

602 : {

603 : unsigned char b;

604 :

605 : b = ~PORT4.PORT.BIT.B0 & 0x01; /* Read start bar signal */

606 :

607 : return b;

608 : }

The start bar detection sensor is connected to bit 4 of port 4. The bits other than bit 4 of port 4 do not interest us,

so bit operations are used to fetch the value of only the bit associated with the sensor.

The operation of the startbar_get function when the start bar is present is illustrated below.

7

6

5

4

3

2

1

0

Read.

0

?

1

0

1

Line 605: Read bit0 of port 4.

Line 605: Invert

Line 605: Apply 0x01

mask value.

Result.

Start bar

0

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5.4.20. led_out_m Function (LED Control in MCU board)

The led_out_m function turns on and off LED0, LED1, LED2, and LED3 on the MCU board.

704 : /***********************************************************************/

705 : /* LED control in MCU board */

706 : /* Arguments: Switch value, LED0: bit 0, LED1: bit 1. 0: dark, 1: lit */

707 : /* */

708 : /***********************************************************************/

709 : void led_out_m( unsigned char led )

710 : {

711 : led = ~led;

712 : PORTA.DR.BYTE = led & 0x0f;

713 : }

The operation of the led_out function when the value of the argument is 2 is illustrated below.

7

6

5

4

3

2

1

0

1

0

1

0

?

0

1

0

1

Argument = A

Line 707: Invert.

Line 708: Apply 0x0ｆ mask

value

LED3:ON

0

1

0

1

Result.

LED2:OFF

LED1:ON

LED0:OFF

711

712

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5.4.21. led_out Function (LED Control)

The led_out function turns on and off LED3 and LED2 on the motor drive board.

The correspondence between the argument supplied to the function and the illumination status of LED3 and LED2

is as follows:

Argument

Binary

LED3

LED2

0

0 0

OFF

1

0 1

OFF

ON

2

1 0

ON

OFF

3

1 1

ON

715 : /***********************************************************************/

716 : /* LED control in motor drive board */

717 : /* Arguments: Switch value, LED0: bit 0, LED1: bit 1. 0: dark, 1: lit */

718 : /* Example: 0x3 -> LED1: ON, LED0: ON, 0x2 -> LED1: ON, LED0: OFF */

719 : /***********************************************************************/

720 : void led_out( unsigned char led )

721 : {

722 : led = ~led;

723 : PORT7.DR.BIT.B6 = led & 0x01;

724 : PORT1.DR.BIT.B0 = ( led >> 1 ) & 0x01;

725 : }

Be careful that LED2 should be connected to bit0 of port1 and LED3 should be connected to bit6 of port7.

The operation of the led_out function when the value of the argument is 2 is illustrated below.

7

6

5

4

3

2

1

0

1

0

1

0

1

Argument = 2

Line 722: Invert.

Line 723: Apply 0x01 mask

value

1

LED3: OFF

LED2: ON

bit 6 of Port 7

1

0

1

0

1

0

1

6

0

1

0

1

bit 0 of Port 1

Line 724:Shift 1bit to right.

Apply 0x01 mask value

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

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5.4.22. motor Function (Motor Speed Control)

The motor function generates PWM output to the left and right motors. Forward and reverse operation is

controlled by the sign of the argument.

727 : /***********************************************************************/

728 : /* Motor speed control */

729 : /* Arguments: Left motor: -100 to 100, Right motor: -100 to 100 */

730 : /* Here, 0 is stopped, 100 is forward, and -100 is reverse. */

731 : /* Return value: None */

732 : /***********************************************************************/

733 : void motor( int accele_l, int accele_r )

734 : {

735 : int sw_data;

736 :

737 : sw_data = dipsw_get() + 5;

738 : accele_l = accele_l * sw_data / 20;

739 : accele_r = accele_r * sw_data / 20;

740 :

741 : /* Left Motor Control */

742 : if( accele_l >= 0 ) {

743 : PORT7.DR.BYTE &= 0xef;

744 : MTU4.TGRC = (long)( PWM_CYCLE - 1 ) * accele_l / 100;

745 : } else {

746 : PORT7.DR.BYTE |= 0x10;

747 : MTU4.TGRC = (long)( PWM_CYCLE - 1 ) * ( -accele_l ) / 100;

748 : }

749 :

750 : /* Right Motor Control */

751 : if( accele_r >= 0 ) {

752 : PORT7.DR.BYTE &= 0xdf;

753 : MTU4.TGRD = (long)( PWM_CYCLE - 1 ) * accele_r / 100;

754 : } else {

755 : PORT7.DR.BYTE |= 0x20;

756 : MTU4.TGRD = (long)( PWM_CYCLE - 1 ) * ( -accele_r ) / 100;

757 : }

758 : }

(1) Using the motor Function

The use of the motor function is described below.

motor(left motor PWM value, right motor PWM value );

The arguments are assigned the left motor PWM value and right motor PWM value, separated by a comma. The

correspondence between the PWM values and motor operation are as follows:

Value

Description

-100 to -1

The motor operates in the reverse direction. A value of –100 corresponds to “reverse 100%.”

The value cannot exceed –100. The setting must be an integer value.

0

The motor is stopped.

1 to 100

The motor operates in the forward direction. A value of 100 corresponds to “forward 100%.”

The value cannot exceed 100. The setting must be an integer value.

MCU Car Kit, Ver. 5.1 Program Explanation Manual - kit12_rx62t Version (Version for RX62T)

83

The actual motor output ratios are as follows:

PWM output to left motor = left motor PWM value set by motor function × DIP switch value + 5 / 20

PWM output to right motor = right motor PWM value set by motor function × DIP switch value + 5 / 20

For example, it is not actually the case that the left motor operates in the forward direction at 80% when the left

motor PWM value set by the motor function is 80. The actual PWM ratio output to the motor differs depending on

the setting of the DIP switches on the MCU board.

Let’s assume that the following line of code is processed when the DIP switch setting is 1100 (12 in decimal

notation):

motor( -70 , 100 );

The actual PWM values output to the motors will be as follows:

PWM output to left motor = –70 × (12 + 5) ÷ 20 = –70 × 0.85 = –59.5 = –59%

PWM output to right motor = 100 × (12 + 5) ÷ 20 = 100 × 0.85 = 85%

The calculation result for the left motor is –59.5%, but the portion after the decimal point is discarded to produce

an integer value. Thus, the PWM value output to the left motor is reverse 59% and the PWM value output to the

right motor is forward 85%.

The manner in which the above is processed in practice is described below.

(2) Change to PWM Value According to DIP Switch Setting

737 : sw_data = dipsw_get() + 5; dipsw_get() = DIP switch value of 0 to 15

738 : accele_l = accele_l * sw_data / 20;

739 : accele_r = accele_r * sw_data / 20;

Line 737

This assigns a value of (DIP switch value + 5) to variable sw_data. The range of DIP switch values

is 0 to 15, so variable sw_data can have a value of 5 to 20.

Line 738

The PWM value ratio applied to the left motor is assigned to the variable accele_l on the left of the

equal sign. The value of the variable accele_l on the right of the equal sign is the left motor PWM

value set by the motor function. Thus, the PWM value applied to the left motor can be calculated as

follows:

accele_l = accele_l (left motor PWM value set by motor function)×sw_data/20

Variable accele_l can have a value within a range of –100 to 100.

Line 739

The PWM value ratio applied to the right motor is assigned to the variable accele_r on the left of

the equal sign. The value of the variable accele_r on the right of the equal sign is the right motor

PWM value set by the motor function. Thus, the PWM value applied to the right motor can be

calculated as follows:

accele_r = accele_r (right motor PWM value set by motor function)×sw_data/20

Variable accele_r can have a value within a range of –100 to 100.

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(3) Left Motor Control

This portion of the function controls the left motor. The left motor PWM output is on pin P72. The PWM output

on pin P72 is specified by the PWM value setting in MTU3_4 timer general register A (MTU4.TGRA). However,

this setting is not made directly but to MTU3_4 timer general register C (MTU4.TGRC), which functions as a

buffer register, instead.

741 : /* Left Motor Control */

742 : if( accele_l >= 0 ) {

743 : PORT7.DR.BYTE &= 0xef;

744 : MTU4.TGRC = (long)( PWM_CYCLE - 1 ) * accele_l / 100;

745 : } else {

746 : PORT7.DR.BYTE |= 0x10;

747 : MTU4.TGRC = (long)( PWM_CYCLE - 1 ) * ( -accele_l ) / 100;

748 : }

Line 742

Checks whether the left motor PWM value ratio is a positive or a negative value. If positive, lines

743 and 744 are processed, if negative, lines 746 and 747.

Lines 743

to 744

If the value is positive, lines 743 and 744 are processed.

P74 is cleared to 0 and PWM is output on P72, causing the left motor to operate in the forward

direction according to the PWM ratio.

Line 743 performs the following bit operations and clears pin P74 to 0:

bit

7

6

5

4

3

2

1

0

Original

value

(port 2)

P76

P75

P74

P73

P72

P71

P70

AND value

1

0

1

Result

P76

P75

0

P73

P72

P71

P70

Line 744 performs the calculation below and sets the PWM value in MTU3_4 timer general register

C (MTU4.TGRC). If there are digits after the decimal point, they are discarded.

MTU4.TGRC

accele_l (0 to 100)

100

= ( PWM_CYCLE - 1 ) 

accele_l (0 to 100)

100

= 24575 

For example, when accele_l = 80 the calculation of the value written to MTU4.TGRC is as follows:

MTU4.TGRC = 24575 80/100 = 19660

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Lines 746

to 747

If the value is negative, lines 746 and 747 are processed.

P74 is set to 1 and PWM is output on P72, causing the left motor to operate in the reverse direction

according to the PWM ratio.

Line 746 performs the following bit operations and sets pin P74 to 1:

bit

7

6

5

4

3

2

1

0

Original

value

(port 2)

P76

P75

P74

P73

P72

P71

P70

OR value

0

1

0

Result

P76

P75

1

P73

P72

P71

P70

Line 747 performs the calculation below and sets the PWM value in timer MTU3_4 timer general

register C (MTU4.TGRC). If there are digits after the decimal point, they are discarded.

MTU4.TGRC

-accele_l (-1 to -100)

100

= ( PWM_CYCLE - 1 ) 

-accele_l (-1 to -100)

100

= 24575 

A key point is that the value of variable accele_l is a negative number. In circuit terms, setting P74

to 1 specifies reverse operation, so accele_l is converted to a positive number for the calculation.

The conversion method is to specify -accele_l in the expression. For example, when accele_l = –50

the calculation of the value written to MUT4.TGRC is as follows:

MTU4.TGRC = 24575  {-(-50)}/100 = 24575  50/100 = 12287.5 = 12287

(4) Right Motor Control

This portion of the function controls the right motor. The right motor PWM output is on pin P73. The PWM output

on pin P73 is specified by the PWM value setting in MTU3_4 timer general register B (MTU4.TGRB). However,

this setting is not made directly but to MTU3_4 timer general register D (MTU4.TGRD), which functions as a

buffer register, instead.

750 : /* Right Motor Control */

751 : if( accele_r >= 0 ) {

752 : PORT7.DR.BYTE &= 0xdf;

753 : MTU4.TGRD = (long)( PWM_CYCLE - 1 ) * accele_r / 100;

754 : } else {

755 : PORT7.DR.BYTE |= 0x20;

756 : MTU4.TGRD = (long)( PWM_CYCLE - 1 ) * ( -accele_r ) / 100;

757 : }

758 : }

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Line 751

Checks whether the left motor PWM value ratio is a positive or a negative value. If positive, lines

752 and 753 are processed, if negative, lines 755 and 756.

Lines 752

to 753

If the value is positive, lines 752 and 753 are processed.

P75 is cleared to 0 and PWM is output on P73, causing the right motor to operate in the forward

direction according to the PWM ratio.

Line 752 performs the following bit operations and clears pin P75 to 0:

bit

7

6

5

4

3

2

1

0

Original

value

(port 7)

P76

P75

P74

P73

P72

P71

P70

AND value

1

0

1

Result

P76

0

P74

P73

P72

P71

P70

Line 753 performs the calculation below and sets the PWM value in MTU3_4 timer general register

D (MTU4.TGRD). If there are digits after the decimal point, they are discarded.

MTU4.TGRD

accele_r (0 to 100)

100

= ( PWM_CYCLE - 1 ) 

accele_r (0 to 100)

100

= 24575 

For example, when accele_r = 20 the calculation of the value written to MTU4.TGRD is as follows:

MTU4.TGRD = 24575  20/100 = 4915

Lines 755

to 756

If the value is negative, lines 755 and 756 are processed.

P75 is set to 1 and PWM is output on P73, causing the right motor to operate in the reverse direction

according to the PWM ratio.

Line 755 performs the following bit operations and sets pin P75 to 1:

bit

7

6

5

4

3

2

1

0

Original

value

(port 7)

P76

P75

P74

P73

P72

P71

P70

OR value

0

1

0

Result

P76

1

P74

P73

P72

P71

P70

Line 756 performs the calculation below and sets the PWM value in MTU3_4 timer general register

D (MTU4.TGRD). If there are digits after the decimal point, they are discarded.

MTU4.TGRD

-accele_r (-1 to -100)

100

= ( PWM_CYCLE - 1 )

-accele_r (-1 to -100)

100

= 24575 

A key point is that the value of variable accele_r is a negative number. In circuit terms, setting P2_3

to 1 specifies reverse operation, so accele_r is converted to a positive number for the calculation.

The conversion method is to specify -accele_r in the expression. For example, when accele_r = –90

the calculation of the value written to TRDGRC1 is as follows:

MTU4.TGRD = 24575  {-(-90)}/100 = 24575  90/100 = 22117.5 = 22117

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(5) Dip Switch Value and Motor Output

When the motor function setting is 100%, the DIP switch setting determines the actual output, as follows:

DIP Switch

Decimal

Calculation

Motor Ratio

P60

P61

P62

P63

0

5/20

25%

0

1

6/20

30%

0

1

0

2

7/20

35%

0

1

3

8/20

40%

0

1

0

4

9/20

45%

0

1

0

1

5

10/20

50%

0

1

0

6

11/20

55%

0

1

7

12/20

60%

1

0

8

13/20

65%

1

0

1

9

14/20

70%

1

0

1

0

10

15/20

75%

1

0

1

11

16/20

80%

1

0

12

17/20

85%

1

0

1

13

18/20

90%

1

0

14

19/20

95%

1

15

20/20

100%

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5.4.23. handle Function (Servo Steering Operation)

760 : /***********************************************************************/

761 : /* Servo steering operation */

762 : /* Arguments: servo operation angle: -90 to 90 */

763 : /* -90: 90-degree turn to left, 0: straight, */

764 : /* 90: 90-degree turn to right */

765 : /***********************************************************************/

766 : void handle( int angle )

767 : {

768 : /* When the servo move from left to right in reverse, replace "-" with "+". */

769 : MTU3.TGRD = SERVO_CENTER - angle * HANDLE_STEP;

770 : }

(1) Using the handle Function

The use of the handle function is described below.

handle( Servo angle );

The argument specifies the servo angle. The correspondence between the value and the servo angle is as follows:

Value

Description

Negative

The servo turns to the left the specified number of degrees.

0

The servo is oriented to 0 degrees (straight ahead). If the servo does not point straight ahead

when the setting value is 0, the SERVO_CENTER value is off and requires adjustment.

Positive

The servo turns to the right the specified number of degrees.

Observe the following code examples:

handle( 0 ); 0 degree

handle( 30 ); Right 30 degrees

handle( -45 ); Left 45 degrees

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(2) Program Description

765 : MTU3.TGRD = SERVO_CENTER - angle * HANDLE_STEP;

[1] [2] [3] [4]

[1]

The PWM on width setting for pin P71, which is connected to the servo, is specified by the setting of

MTU3.TGRB. However, this setting is not made directly but to MTU3.TGRD, which functions as a buffer

register, instead.

[2]

Value corresponding to 0 degrees.

[3]

The angle specified by the handle function is assigned to this variable.

[4]

Among of increase equivalent to 1 degree.

The examples below illustrate the calculation of the value assigned to MTU3.TGRD.

Note: In these examples, SERVO_CENTER = 2320 and HANDLE_STEP = 13.

 0 degrees

MTU3.TGRD = SERVO_CENTER - angle * HANDLE_STEP

= 2320 - 0 * 13

= 2320

 30 degrees

MTU3.TGRD = SERVO_CENTER - angle * HANDLE_STEP

= 2320 - 30 * 13

= 2320 - 390

= 1930

 –45 degrees

MTU3.TGRD = SERVO_CENTER - angle * HANDLE_STEP

= 2320 - (-45) * 13

= 2320 - (-585)

= 2905

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5.4.24. Start

This is the main function. It is the first C language program to be called from the startup routine and run.

66 : /***********************************************************************/

67 : /* Main program */

68 : /***********************************************************************/

69 : void main(void)

70 : {

71 : /* Initialize MCU functions */

72 : init();

73 :

74 : /* Initialize micom car state */

75 : handle( 0 );

76 : motor( 0, 0 );

Line 72

This function initialises the on-chip peripheral functions of the RX62T MCU.

Lines 75

to 76

This initialises the state of the MCU car.

The servo angle is set to 0 degrees by the handle function.

The left motor and right motor are set to 0% by the motor function.

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5.4.25. Patterns

In kit12_rx62t.c a method called patterns is used to organize the program.

This basically involves dividing the program up into small sections. For example, there is a section for button

input standby processing, one for checking whether or not a start bar is present, and so on.

Next, a variable called pattern is created. This makes it possible to select the program section to be run by setting

the value of the variable pattern.

For example, setting the value of variable pattern to 0 causes button input standby processing to be performed,

setting variable pattern to 1 causes processing to check whether or not a start bar is present to be performed, and

so on.

Using this method of dividing the processing into various patterns makes the program code easier to read. Such

use of patterns is sometimes called modular programming.

5.4.26. Writing a Program

When writing a C language program with patterns, switch statements are used for branching. This is shown in the

following flowchart:

Program start

init();

handle( 0 );

motor( 0, 0 );

Pattern 0

Pattern 1

Pattern 11

Pattern 12

Pattern 13

Pattern …

Pattern 63

case 0:

case 1:

case 63:

...

case 11:

Pattern 64

case 64:

case 12:

case 13:

switch( pattern )

Initialize micom car state

Branch using switch statement.

At startup, the value of variable pattern is 0. The switch statement causes execution to continue with pattern 0,

which is the portion of the program corresponding to case 0. This will be described in detail later, but pattern 0 is

button input standby processing. When the button is depressed, pattern=1 is executed. This is shown in the

following figure:

Program start

init();

handle( 0 );

motor( 0, 0 );

Pattern 0

Button depressed?

When depressed, pattern=1

Pattern 1

Pattern 11

Pattern 12

Pattern 13

Pattern 21

Pattern 22

case 0:

case 1:

case 22:

case 21:

case 11:

case 12:

case 13:

switch( pattern )

Initialize micom car state

Branch using switch statement.

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The value of variable pattern is 1 the next time the switch statement is executed, so the portion of the program

corresponding to case 1 is run. In this program, running the portion of the program corresponding to switch

( pattern ) case 1 means running pattern 1.

Pattern 1 is the portion of the program that checks whether or not the start bar is open. The processing flow is as

follows:

Program start

init();

handle( 0 );

motor( 0, 0 );

Pattern 1

Start bar open?

Not open, so do nothing.

Pattern 0

Pattern 11

Pattern 12

Pattern 13

Pattern 21

Pattern 22

switch( pattern )

Initialize micom car state

Branch using switch statement.

case 0:

case 1:

case 22:

case 21:

case 11:

case 12:

case 13:

As the above illustrates, the program has a modular organization. Each module performs a simple check, such as

“start button depressed?” or “start bar open?”, and changes the pattern number (the value of variable pattern)

when the condition it met.

The program code is as follows. It uses ordinary switch and case statements.

switch( pattern ) {

case 0:

/* pattern=0 processing */

break;

case 1:

/* pattern=1 processing */

break;

default:

/* if neither */

break;

}

The value of pattern is compared to the values

defined in the various case statements, and

execution jumps to the case position whose

value matches.

Processing ends when a break statement or the

end of the switch statement is encountered.

If none of the values defined in the case

statements matches, the default statement is

executed. Incidentally, nothing is executed if

there is no default statement.

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5.4.27. Pattern Descriptions

The pattern numbers used in kit12_rx62t.c, the processing performed by each pattern, and the conditions for

changes between patterns are listed below.

Current

pattern

Processing description

Pattern change condition

0

Wait for button input

 When button depressed, to pattern 1

1

Check if start bar is open

 When start bar open detected, to pattern 11

11

Normal trace

 At large turn to right, to pattern 12

 At large turn to left, to pattern 13

 When crossline detected, to pattern 21

 When right half line detected, to pattern 51

 When left half line detected, to pattern 61

12

Check end of large turn to

right

 When large turn to right completed, to pattern 11

 When crossline detected, to pattern 21

 When right half line detected, to pattern 51

 When left half line detected, to pattern 61

13

Check end of large turn to

left

 When large turn to left completed, to pattern 11

 When crossline detected, to pattern 21

 When right half line detected, to pattern 51

 When left half line detected, to pattern 61

21

Processing at 1st crossline

detection

 When servo and speed settings completed, to pattern 22

22

Read but ignore 2nd time

 After 100 ms, to pattern 23

23

Trace, crank detection after

crossline

 When left crank detected, to pattern 31

 When right crank detected, to pattern 41

31

Clearing from Left crank

- wait until stable

 After 200 ms, to pattern 32

32

Clearing from Left crank

- check end of turn

 After clearing from left crank, to pattern 11

41

Clearing from Right crank

- wait until stable

 After 200 ms, to pattern 42

42

Clearing from Right crank

- check end of turn

 After clearing from right crank, to pattern 11

51

Processing at 1st right half

line detection

 When servo and speed settings completed, to pattern 52

52

Read but ignore 2nd time

 After 100 ms, to pattern 53

53

Trace after right half line

 If centre line disappears, turn steering wheel to right and go to

pattern 54

54

Right lane change end check

 When new centre line is at sensor centre position, to pattern 11

61

Processing at 1st left half line

detection

 When servo and speed settings completed, to pattern 62

62

Read but ignore 2nd time

 After 100 ms, to pattern 63

63

Trace after left half line

 If centre line disappears, turn steering wheel to left and go to

pattern 64

64

Left lane change end check

 When new centre line is at sensor centre position, to pattern 11

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5.4.28. Initial while and switch when Using Patterns

78 : while( 1 ) {

79 : switch( pattern ) {

105 : case 0:

Pattern 0 processing

119 : break;

120 :

121 : case 1:

Pattern 1 processing

137 : break;

Pattern processing

473 : default:

474 : /* If neither, return to standby state */

475 : pattern = 0;

476 : break;

477 : }

478 : }

while( 1 ) { in line 78 and } in line 478 form a pair, and switch( pattern ) { in line 79 and } in line 477 form a pair.

Generally speaking, lines enclosed between opening and closing curly brackets { } are indented four characters

to make the code easier to read. This convention is generally followed in the code listing of this program. However,

the lines containing while and switch are not indented. This is to prevent complex lines from exceeding the right

margin and being split into two lines in the listing, which would be more difficult to read. After all, the reason for

indenting some lines is to make the code listing easier to read. Extra spaces at the beginning of lines have no effect

when the code is compiled. However, if this exception is bothersome, feel free to indent lines 79 to 477 by adding

four spaces at the beginning of each line.

while( condition ) is a control statement that causes the code enclosed in the curly brackets { } to be executed

repeatedly for as long as the condition is true, and the code following the curly brackets { } to be executed when

the condition is false.

while( condition true ) {

…

}

while( condition false ) {

…

}

…

“True” and “false” are defined as follows:

Description

Example

True

Correct, other than 0

3 < 5 3==3 1 2 3 -1 -2 -3

False

Not correct, 0

5 < 3 3==6 0

The code listing reads while( 1 ). A value of 1 is always true, so the code enclosed in the curly brackets { } is

repeated infinitely. In a Windows program, for example, such an infinite loop would be a problem because it

would prevent the user from quitting the application. But since our program is designed to operate a MCU car,

there is no problem. Once the MCU car crosses the finish line (or runs off the course), someone can pick it up and

Pair

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switch it off. On the other hand, if the MCU were to fail to complete its processing correctly and execution of the

program ended, processing would continue into an area of memory containing no executable code, resulting in

unpredictable behaviour. The usual approach in MCU car programs is to have the MCU repeatedly do nothing

(enter an endless loop) without exiting the program or to have it transition to a low-power mode called sleep mode,

in which operation stops and the MCU waits to be awakened.

5.4.29. Pattern 0: Wait For Button Input

Pattern 0 is the section of the program that checks whether or not the pushbutton has been depressed. While this

checking is taking place, there is no way to know whether the program is running or not. To provide such an

indication, LED0 and LED1 are illuminated alternately.

First is the section for detecting pushbutton input. The pushsw_get function checks the pushbutton state. It returns

a value of 1 when the button is depressed, so the code enclosed in the curly brackets is executed and the value of

pattern is set to 1.

105 : case 0:

106 : /* Wait for switch input */

107 : if( pushsw_get() ) {

108 : pattern = 1;

109 : cnt1 = 0;

110 : break;

111 : }

 If button depressed (return value other than 0)…

Set pattern to 1.

Clear cnt1 to 0.

End switch statement.

Line 107

When the pushbutton is depressed, the code enclosed in the curly brackets (lines 102 to 104) is

executed. Nothing is executed if the pushbutton is not depressed.

The if statement performs a comparison. The following line compares the return value of the

pushsw_get function with the value 1:

if( pushsw_get() == 1 ) { If the return value of the pushsw_get function is 1...

But our code listing reads as follows:

if( pushsw_get() ) {

There is no value provided for comparison. In the C language, the meaning is as follows:

if( Value ) {

If the value is other than 0, the condition is considered true and this section is executed.

} else {

If the value is other than 0, the condition is considered true and this section is executed.

}

The return value of the pushsw_get function is 1 when the button is in the depressed state and 0

when it is not depressed. Therefore, operation is as follows when the pushbutton is depressed:

if( 1 ) { pushsw_get() returns a value of 1.

The value is other than 0, so the code between the curly brackets is executed.

}

Line 108

The value 1 is assigned to variable pattern. The case 1: portion of the program is run the next time

the switch-case statement is executed.

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After this are added the lines that cause the LEDs to turn on and off. First LED2 lights for 0.1 second, then LED3

lights for 0.1 second, then the sequence is repeated.

112 : if( cnt1 < 100 ) {

113 : led_out( 0x1 );

114 : } else if( cnt1 < 200 ) {

115 : led_out( 0x2 );

116 : } else {

117 : cnt1 = 0;

118 : }

Is value of cnt1 0 to 99?

If so, light LED2 only.

Is value of cnt1 100 to 199?

If so, light LED3 only.

If value of cnt1 is something else (200 or greater)…

Clear cnt1 to 0.

Most variables, such as the variable pattern, do not change value once set until they are explicitly set to a new

value. In kit12_rx62t.c, variables cnt0 and cnt1 only are exceptions to this. Variables cnt0 and cnt1 are each

incremented (+1) every 1 ms by the interrupt function. This means these variables can be used to measure time.

The purpose of the break statement in line 113 is to end case 0.

78 : while( 1 ) {

79 : switch( pattern ) {

105 : case 0:

Lines omitted

119 : break;

Lines omitted

477 : }

478 : }

[1]

The break statement in line 119 causes control to jump to the next line after line 477, which contains the

closing curly bracket of the switch-case statement.

[2]

Line 478 is processed next, but since it contains the closing curly bracket of a while statement matching

the opening curly bracket in line 78, control returns to line 78.

[3]

The switch-case statement starting on line 79 is processed, and control moves to a case statement

according to the value of variable pattern.

[1]

[2]

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Note: Not Using Variable cnt1

What if we used the timer function instead of cnt1?

if( pushsw_get() ) {

pattern = 1;

cnt1 = 0;

break;

}

timer( 100 );  This line triggers a pause of 100 ms!!

led_out( 0x1 );

timer( 100 );  This line triggers a pause of 100 ms!!

led_out( 0x2 );

break;

This is simpler. Maybe this approach is better. But the timer function does nothing but wait for a period of time

to elapse. If the pushbutton is depressed and then released while the timer function is executing, the button may

no longer be in the depressed state when the pushsw_get function executes. The depress would not be detected in

that case. In this example code the timer function takes 0.1 seconds to run, so you would have to depress and

release the button very quickly for it not to be detected. However, if the duration was longer, say, several seconds,

the periods when the button state was not being checked would be too long and it would not be possible to detect

depresses reliably. This is why variable cnt1 is used to check the time while the button state checking is

taking place.

5.4.30. Pattern 1: Check if Start Bar Is Open

Pattern 1 is the section of the program that checks whether or not the start bar is open. While this checking is

taking place, there is no way to know whether the program is running or not. To provide such an indication, LED2

and LED3 are illuminated alternately.

First is the section for detecting whether the start bar is open or closed.

121 : case 1:

122 : /* Check if start bar is open */

123 : if( !startbar_get() ) {

124 : /* Start!! */

125 : led_out( 0x0 );

126 : pattern = 11;

127 : cnt1 = 0;

128 : break;

129 : }

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Line 123

If the start bar is open, the code enclosed in the curly brackets (lines 125 to 128) is executed. Nothing

is executed if it is closed.

The startbar_get function returns a value of 1 when the start bar is present (the sensors produce a

response) and a value of 0 when the start bar is absent (the sensors produce no response). The code is

analogous to that used in the pushsw_get function described earlier.

if( startbar_get() ) {

Execute this code if the start bar is present.

}

This would mean the code between the curly brackets would be executed if the start bar were present.

We actually want this code to run if the start bar is not present. Therefore, we add an exclamation

mark ! to negate the statement, so now the code between the curly brackets is executed if the start bar

is absent. The exclamation mark ! means negation.

if( ! Value ) {

If the value is not other than 0, this section is executed.  This section is executed if the

value is 0.

} else {

If the value is not 0, this section is executed.  This section is executed if the value is

other than 0.

}

This results in the following:

if( !startbar_get() ) {

If the start bar is not present, this section is executed.

}

Line 126

The value 11 is assigned to variable pattern. The case 11: portion of the program is run the next time

the switch-case statement is executed.

Line 128

The break statement causes control to jump to the closing curly bracket of the switch-case statement.

Next come lines that cause the LEDs to turn on and off. First LED2 lights for 0.05 seconds, then LED3 lights for

0.05 seconds, then the sequence is repeated. The flashing is faster than in pattern 1, so you know that the MCU car

is waiting for the start bar to open.

130 : if( cnt1 < 50 ) {

131 : led_out( 0x1 );

132 : } else if( cnt1 < 100 ) {

133 : led_out( 0x2 );

134 : } else {

135 : cnt1 = 0;

136 : }

137 : break;

 Is value of cnt1 0 to 49?

 If so, light LED0 only.

 Is value of cnt1 50 to 99?

 If so, light LED1 only.

 If value of cnt1 is something else (100 or greater)...

 Clear cnt1 to 0.

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5.4.31. Pattern 11: Normal Trace

Pattern 11 is a status in which the program reads the sensor data and controls the left motor, right motor, and servo.

First, let’s imagine the possible sensor states. There are eight sensors, but if we tried to make use of them all we

would have to deal with too much detection state data and the program code would become overly complex.

Instead, we will apply masking with MASK3_3 and use data from a total of six sensors, three on the right and

three on the left, to determine the state of the course.

Next, let’s consider the turn angle as well as the left motor and right motor PWM values. The idea is that we will

keep the steering wheel pointed straight ahead and increase the speed when the sensors indicate that the MCU car

is in the centre of the track. When the sensors indicate that the MCU car has deviated from the centre, we will turn

the steering wheel and lower the speed of the left and right motors.

This works as follows in kit07_rx62t.c:

Course and sensor state

Value read

by sensors

Hexadecimal

Steering

angle

Left

motor

PWM

Right

motor

PWM

1

●●●××●●●

00000000

0x00

0

100

2

●●●××○●●

00000100

0x04

5

100

3

●●●××○○●

00000110

0x06

10

80

67

4

●●●××○○○

00000111

0x07

15

50

38

5

●●●××●○○

00000011

0x03

25

30

19

6

●●○××●●●

00100000

0x20

-5

100

7

●○○××●●●

01100000

0x60

-10

67

80

8

○○○××●●●

11100000

0xe0

-15

38

50

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9

○○●××●●●

11000000

0xc0

-25

19

30

The MCU car course also includes crosslines, right half lines, and left half lines. There are functions designed to

detect each of these, and we will make use of them.

Course and sensor state

Course feature and

processing

Function used for checking

10

○○○××○○○

6 sensors used

Horizontal line (crossline)

↓

When detected, to crank

processing (pattern 21)

check_crossline

1１

●●●○○○○○

8 sensors used

Horizontal line from centre

to right edge only

(right half line)

↓

When detected, to right half

line processing (pattern 51)

check_rightline

1２

○○○○○●●●

8 sensors used

Horizontal line from centre

to left edge only

(left half line)

↓

When detected, to left half

line processing (pattern 61)

check_leftline

We will write the program code using the above tables as a basis.

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(1) Read Sensors

153 : switch( sensor_inp(MASK3_3) ) {

This reads the state of the sensors. MASK3_3 is used so that three sensors on the right and three on the left are

read. A switch-case statement is used to branch to different locations in the program code according to the sensor

state.

(2) Straight Forward

154 : case 0x00:

155 : /* Center -> straight */

156 : handle( 0 );

157 : motor( 100 ,100 );

158 : break;

This is the state when the sensor value is 0x00. In this state the MCU car is moving straight forward, as shown in

the figure below. It proceeds using the following setting values: servo angle 0 degrees, left motor 100%, the right

motor 100%.

(3) Slight Amount Left of Centre

160 : case 0x04:

161 : /* Slight amount left of center -> slight turn to right */

162 : handle( 5 );

163 : motor( 100 ,100 );

164 : break;

This is the state when the sensor value is 0x04. In this state the MCU car is positioned a slight amount to the left

of centre, as shown in the figure below. It proceeds using the following setting values in order to move back to the

centre position: servo angle 5 degrees right, left motor 100%, and right motor 100%.

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(4) Small Amount Left of Centre

166 : case 0x06:

167 : /* Small amount left of center -> small turn to right */

168 : handle( 10 );

169 : motor( 80 ,67 );

170 : break;

This is the state when the sensor value is 0x06. In this state the MCU car is positioned a small amount to the left of

centre, as shown in the figure below. It proceeds using the following setting values and at reduced speed in order

to move back to the centre position: servo angle 10 degrees right, left motor 80%, and right motor 67%.

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(5) Medium Amount Left of Centre

172 : case 0x07:

173 : /* Medium amount left of center -> medium turn to right */

174 : handle( 15 );

175 : motor( 50 ,38 );

176 : break;

This is the state when the sensor value is 0x07. In this state the MCU car is positioned a medium amount to the left

of centre, as shown in the figure below. It proceeds using the following setting values and at reduced speed in

order to move back to the centre position: servo angle 15 degrees right, left motor 50%, and right motor 38%.

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(6) Large Amount Left of Centre

178 : case 0x03:

179 : /* Large amount left of center -> large turn to right */

180 : handle( 25 );

181 : motor( 30 ,19 );

183 : break;

Note: The actual program code starts from line 182. The description here is abbreviated, but details are

provided later in this manual.

This is the state when the sensor value is 0x03. In this state the MCU car is positioned a large amount to the left of

centre, as shown in the figure below. It proceeds using the following setting values and at reduced speed in order

to move back to the centre position: servo angle 25 degrees right, left motor 30%, and right motor 19%.

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(7) Slight Amount Right of Centre

185 : case 0x20:

186 : /* Slight amount right of center -> slight turn to left */

187 : handle( -5 );

188 : motor( 100 ,100 );

189 : break;

This is the state when the sensor value is 0x20. In this state the MCU car is positioned a slight amount to the right

of centre, as shown in the figure below. It proceeds using the following setting values in order to move back to the

centre position: servo angle 5 degrees left, left motor 100%, and right motor 100%.

(8) Small Amount Right of Centre

191 : case 0x60:

192 : /* Small amount right of center -> small turn to left */

193 : handle( -10 );

194 : motor( 67 ,80 );

195 : break;

This is the state when the sensor value is 0x60. In this state the MCU car is positioned a small amount to the right

of centre, as shown in the figure below. It proceeds using the following setting values and at reduced speed in

order to move back to the centre position: servo angle 10 degrees left, left motor 67%, and right motor 80%.

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(9) Medium Amount Right of Centre

197 : case 0xe0:

198 : /* Medium amount right of center -> medium turn to left */

199 : handle( -15 );

200 : motor( 38 ,50 );

201 : break;

This is the state when the sensor value is 0xe0. In this state the MCU car is positioned a medium amount to the

right of centre, as shown in the figure below. It proceeds using the following setting values and at reduced speed in

order to move back to the centre position: servo angle 15 degrees left, left motor 38%, and right motor 50%.

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(10) Large Amount Right of Centre

203 : case 0xc0:

204 : /* Large amount right of center -> large turn to left */

205 : handle( -25 );

206 : motor( 19 ,30 );

208 : break;

Note: The actual program code starts from line 207. The description here is abbreviated, but details are

provided later in this manual.

This is the state when the sensor value is 0xc0. In this state the MCU car is positioned a large amount to the right

of centre, as shown in the figure below. It proceeds using the following setting values and at reduced speed in

order to move back to the centre position: servo angle 25 degrees left, left motor 19%, and right motor 30%.

(11) Check Crossline

141 : if( check_crossline() ) { /* Cross line check */

142 : pattern = 21;

143 : break;

144 : }

The check_crossline function returns a value of 0 to indicate no crossline detected and 1 to indicate crossline

detected. When a crossline is detected, pattern is set to 21 and a break statement is used to end processing of the

switch-case statement. Crossline checking is important, so this code is executed before the normal trace program

code.

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(12) Right Half Line

145 : if( check_rightline() ) { /* Right half line detection check */

146 : pattern = 51;

147 : break;

148 : }

The check_rightline function returns a value of 0 to indicate no right half line detected and 1 to indicate right half

line detected. When a right half line is detected, pattern is set to 51 and a break statement is used to end

processing of the switch-case statement. Right half line checking is important, so this code is executed before the

normal trace program code.

(13) Left Half Line

149 : if( check_leftline() ) { /* Left half line detection check */

150 : pattern = 61;

151 : break;

152 : }

The check_leftline function returns a value of 0 to indicate no left half line detected and 1 to indicate left half line

detected. When a left half line is detected, pattern is set to 61 and a break statement is used to end processing of

the switch-case statement. Left half line checking is important, so this code is executed before the normal trace

program code.

(14) Other

210 : default:

211 : break;

When a pattern other than those described above is encountered, control jumps to this default section, which does

nothing.

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(15) Position of break Statements to Terminate Execution

A break statement is used to terminate execution of a switch statement or a for, while, or do-while loop. When a

break statement is used within overlapping loops, it only terminates one of the loops within which it is

enclosed, and control passes immediately to the outer loop. It is important to remember this point that a break

statement only terminates one of the loops within which it is enclosed.

The positions exited from by break statements within pattern 11 are shown below. These positions differ, so it is

important to examine carefully within which loop the break statement is used.

while( 1 ) {

switch( pattern ) {

Line omitted

case 11:

/* Normal trace */

if( check_crossline() ) {

pattern = 21;

break;

}

if( check_rightline() ) {

pattern = 51;

break;

}

if( check_leftline() ) {

pattern = 61;

break;

}

switch( sensor_inp(MASK3_3) ) {

case 0x00:

/* Center  straight */

handle( 0 );

speed( 100 ,100 );

break;

case 0x04:

/* Slight amount left of centre

 slight turn to right */

handle( 5 );

speed( 100 ,100 );

break;

Line omitted

default:

break;

}2

break;

Line omitted

}1

}

case corresponding to switch( pattern )

break from switch( pattern ), control passes to 1

If statement not terminated!!

break from switch( pattern ), control passes to 1

case corresponding to

switch( sensor_inp(MASK3_3) )

break from switch( sensor_inp(MASK3_3) ),

control passes to 2

case corresponding to

switch( sensor_inp(MASK3_3) )

break from switch( sensor_inp(MASK3_3) ),

control passes to 2

default corresponding to

switch( sensor_inp(MASK3_3) )

break from switch( sensor_inp(MASK3_3) ),

control passes to 2

break from switch( pattern ), control passes to 1

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5.4.32. Pattern 12: Check End of Large Turn to Right

A sensor state of 0x03 indicates the largest amount of skew to left of centre. Therefore, any further move away

from the centre could produce results like those shown in the figure below:

1

This is the sensor state when a large amount left of

centre. The sensor value is 0000 0011. When this

state is encountered, the following lines of code

are executed:

handle( 25 );

motor( 30, 19 );

This causes a turn with the servo angle 25 degrees

right, left motor 30%, and right motor 19%.

2

The leftward skew has increased. The sensor value

is 1000 0001. No code is provided for execution in

this state. Instead, the previous state is maintained.

The previous state was a sensor value of 0000

0011, so the motor speed and servo angle settings

for that sensor state are used.

3

The car has moved even further to the left. The

sensor value is 1100 0000.

4

As shown in the figure at left, a sensor value is

1100 0000 is associated with a state in which the

MCU car is right of centre. The assumption is that

the steering wheel should turn to the left in this

case. Therefore, the following lines of code are

executed:

handle( -25 );

motor( 19, 30 );

This causes a turn with the servo angle 25 degrees

right, left motor 19%, and right motor 30%.

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5

In fact, the MCU car is far to the left of centre.

Turning the steering wheel to the left will cause it

to go off the track.

To prevent this, once a large turn to the right begins the software needs to continue turning the MCU car to the

right until the sensors return to a certain state. Pattern 12 is designed to identify this “certain state.”

case 0x03 portion of pattern 11

178 : case 0x03:

179 : /* Large amount left of center -> large turn to right */

180 : handle( 25 );

181 : motor( 30 ,19 );

182 : pattern = 12; Added: Move to pattern 12.

183 : break;

6

When the sensor value is 0000 0011, control

passes to pattern 12. Pattern 12 is designed to hand

control back to pattern 11 once the sensor value is

0000 0110, one sensor closer to the centre. Let’s

see how this approach works.

7

The sensor value is now 1100 0000. Since it is not

the expected value of 0000 0110, the MCU car

continues to turn to the right. Previously, the

program mistakenly assumed that the MCU car

was too far to the right, but now that we have

pattern 12 this problem does not arise.

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8

The sensor value is now 0110 0000. It is still

not 0000 0110, so the MCU car continues to

turn to the right.

9

The sensor value is now 0000 0100.

The MCU car has almost left the

track, but the program continues to

turn to the right because the sensor

value is not 0000 0110.

Nevertheless, once things get to this

stage the MCU car may go off the

track anyway.

10

The skew to the left has started to be reduced by a

shift to the right, and now the sensor value is 0000

0110. In this state, control returns to pattern 11.

This is the program code based on the above thinking:

case 12:

/* Check end of large turn to right */

if( sensor_inp(MASK3_3) == 0x06 ) {

pattern = 11;

}

break;

But not so fast! Pattern 11 includes checks for crosslines, right half lines, and left half lines. Don’t we need these

in pattern 12 as well?

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11

The sensor value is now 0000 0011, and the

crosslines are ahead. Go to pattern 12.

12

The sensor value is not 0000 0110, so continue

turning to the right.

13

Crossline encountered, so we should switch to

crank detection processing. But pattern 12 only

checks whether or not the sensor value is 0000

0110. This means the MCU car continues on

without detecting the crossline.

As the above illustrates, it may be necessary to

detect crosslines even when pattern 12 processing

is taking place. The same goes for right half line

and left half line checking. So we’ll add these

three types of checks to pattern 12 as well.

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This is the final program code:

215 : case 12:

216 : /* Check end of large turn to right */

217 : if( check_crossline() ) { /* Cross line check during large turn */

218 : pattern = 21;

219 : break;

220 : }

221 : if( check_rightline() ) { /* Right half line detection check */

222 : pattern = 51;

223 : break;

224 : }

225 : if( check_leftline() ) { /* Left half line detection check */

226 : pattern = 61;

227 : break;

228 : }

229 : if( sensor_inp(MASK3_3) == 0x06 ) {

230 : pattern = 11;

231 : }

232 : break;

This is the completed program code for pattern 12.

5.4.33. Pattern 13: Check End of Large Turn to Left

A sensor state of 0xC0 indicates the largest amount of skew to right of centre. Therefore, any further move away

from the centre could produce results like those shown in the figure below:

1

This is the sensor state when a large amount left of

centre. The sensor value is 1100 0000. When this

state is encountered, the following lines of code

are executed:

handle( -25 );

motor( 19, 30 );

This causes a turn with the servo angle 25 degrees

left, left motor 19%, and right motor 30%.

2

The rightward skew has increased. The sensor

value is 1000 0001. No code is provided for

execution in this state. Instead, the previous state

is maintained. The previous state was a sensor

value of 1100 0000, so the motor speed and servo

angle settings for that sensor state are used.

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3

The car has moved even further to the right. The

sensor value is 0000 0011.

4

As shown in the figure at left, a sensor value is

0000 0011 is associated with a state in which the

MCU car is left of centre. The assumption is that

the steering wheel should turn to the right in this

case. Therefore, the following lines of code are

executed:

handle( 25 );

motor( 30, 19 );

This causes a turn with the servo angle 25 degrees

right, left motor 30%, and right motor 19%.

5

In fact, the MCU car is far to the right of centre.

Turning the steering wheel to the right will cause it

to go off the track.

To prevent this, once a large turn to the left begins the software needs to continue turning the MCU car to the left

until the sensors return to a certain state. Pattern 13 is designed to identify this “certain state.”

case 0xc0 portion of pattern 11

203 : case 0xc0:

204 : /* Large amount right of center -> large turn to left */

205 : handle( -25 );

206 : motor( 19 ,30 );

207 : pattern = 13;  Added: Move to pattern 13.

208 : break;

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6

When the sensor value is 1100 0000, control

passes to pattern 13. Pattern 13 is designed to hand

control back to pattern 11 once the sensor value is

0110 0000, one sensor closer to the centre. Let’s

see how this approach works.

7

The sensor value is now 0000 0011. Since it is not

the expected value of 0110 0000, the MCU car

continues to turn to the left. Previously, the

program mistakenly assumed that the MCU car

was too far to the left, but now that we have

pattern 13 this problem does not arise.

8

The sensor value is now 0000 0110. It is still

not 0110 0000, so the MCU car continues to

turn to the left.

9

The sensor value is now 0010 0000.

The MCU car has almost left the

track, but the program continues to

turn to the left because the sensor

value is not 0110 0000.

Nevertheless, once things get to this

stage the MCU car may go off the

track anyway.

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10

The skew to the right has started to be reduced by

a shift to the left, and now the sensor value is 0110

0000. In this state, control returns to pattern 11.

This is the program code based on the above thinking:

case 13:

/* Check end of large turn to left */

if( sensor_inp(MASK3_3) == 0x60 ) {

pattern = 11;

}

break;

But not so fast! Pattern 11 includes checks for crosslines, right half lines, and left half lines. Don’t we need these

in pattern 13 as well?

11

The sensor value is now 1100 0000, and the

crosslines are ahead. Go to pattern 13.

12

The sensor value is not 0110 0000, so continue

turning to the left.

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13

Crossline encountered, so we should switch to

crank detection processing. But pattern 13 only

checks whether or not the sensor value is 0110

0000. This means the MCU car continues on

without detecting the crossline.

As the above illustrates, it may be necessary to

detect crosslines even when pattern 13 processing

is taking place. The same goes for right half line

and left half line checking. So we’ll add these

three types of checks to pattern 13 as well.

This is the final program code:

234 : case 13:

235 : /* Check end of large turn to left */

236 : if( check_crossline() ) { /* Cross line check during large turn */

237 : pattern = 21;

238 : break;

239 : }

240 : if( check_rightline() ) { /* Right half line detection check */

241 : pattern = 51;

242 : break;

243 : }

244 : if( check_leftline() ) { /* Left half line detection check */

245 : pattern = 61;

246 : break;

247 : }

248 : if( sensor_inp(MASK3_3) == 0x60 ) {

249 : pattern = 11;

250 : }

251 : break;

This is the completed program code for pattern 13.

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5.4.34. Crank Overview

Patterns 21 to 42 contain code related to “cranks” (right-angle turns). The figure below provides an overview of

the processing:

[1]

The check_crossline function detects the presence of crosslines. A crossline indicates that 500 mm to 1000

mm ahead is a right or left crank, so the MCU car must apply the brakes to reduce speed in order to

navigate it successfully. In addition, the sensor data is not referenced until position [2] to ensure that the

second crossline does not result in detection of erroneous sensor data.

[2]

This position is the start of the proceed slowly area. The MCU car advances straight ahead along the centre

line.

[3]

When the crank is detected, the MCU car turns in the direction of the crank.

[4]

When the centre line is detected, control returns to pattern 11 and line tracing restarts.

In this way, the MCU car clears from crank. The specifics of the program code used are described below.

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5.4.35. Pattern 21: Processing at 1st Crossline Detection

Control passes to pattern 21 the moment a crossline is detected. First, the MCU car passes over the crosslines. The

characteristics of the portion of track from the position at which the first crossline is discovered to the position

immediately after the second crossline are shown in the following figure:

[1] First crossline

[2] Normal track

[3] Second crossline

[4] Normal track, proceed slowly while tracing centre line

The track, other than the centre line, changes from white to black to white to black again by the time position [4] is

reached. The program must detect these changes and respond appropriately. That sounds pretty complicated.

Let’s look at this in a different way. The distance from position [1] to position [4] is about 100 mm, allowing some

margin for error. (The precise distance is 70 mm: 20 mm for the first crossline + 30 mm of black area + 20 mm for

the second crossline = 70 mm.) If the MCU car is positioned roughly over the centre line and continues to move

forward for about 100 mm while we ignore the sensor data, we’ll probably come out roughly on course. The kit

car includes no mechanism for detecting distances, but we can use the timer to interrupt reading of sensor data for

a specified duration. We don’t know how long a duration yet because that will depend on how fast the MCU car is

travelling. For the time being, let’s use a pause duration of 0.1 seconds and do fine tuning later. In addition, we’ll

make the LEDs on the motor drive board light to indicate externally that processing of pattern 21 has started.

To summarize:

 Illuminate LED2 and LED3.

 Set steering angle to 0 degrees.

 Set PWM value of right and left motors to 0% to initiate brake operation.

 Wait 0.1 seconds.

 After 0.1 seconds elapse, go to next pattern.

This is what the program code of pattern 21 must accomplish.

case 21:

/* Processing at 1st cross line */

led_out( 0x3 );

handle( 0 );

speed( 0 ,0 );

if( cnt1 > 100 ) {

pattern = 22; /* After 0.1 seconds, to pattern 22 */

}

break;

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This is the completed program code. Let’s take a moment to review it. When the value of cnt1 is 100 or greater

(after 100 milliseconds have elapsed), control passes to pattern 22. For this to work as expected, the value of cnt1

must be 0 when pattern 21 starts. For example, if the value of cnt1 is 1000 when control passes to pattern 21, the

value of cnt1 will be judged to be 100 or greater the first time the condition is tested, and control will pass

immediately to pattern 22. Execution of pattern 21 takes place only once (a duration of a few dozen µs) rather than

lasting for 0.1 seconds. We need to add another pattern. Pattern 21 will start brake operation and clear cnt1 to 0,

and pattern 22 will check whether 0.1 seconds have elapsed.

To summarize once again:

Let’s rewrite the program to reflect the above changes.

253 : case 21:

254 : /* Processing at 1st cross line */

255 : led_out( 0x3 );

256 : handle( 0 );

257 : motor( 0 ,0 );

258 : pattern = 22;

259 : cnt1 = 0;

260 : break;

261 :

262 : case 22:

263 : /* Read but ignore 2nd line */

264 : if( cnt1 > 100 ){

265 : pattern = 23;

266 : cnt1 = 0;

267 : }

268 : break;

The portion of the program code from detection of the crossline to the start of the trace centre line area is now

complete.

Hint

When a crossline is detected, the two LEDs on

the motor drive board light. No crossline has

been detected if they do not light.

If crossline detection is not working properly, try

unplugging the motor connectors and pushing the

MCU car forward by hand.

Tasks performed by

pattern 21:

 Illuminate LED2 and LED3.

 Set steering angle to 0 degrees.

 Set PWM value of right and left motors to 0% to initiate brake operation.

 Go to next pattern.

 Clear cnt1.

Tasks performed by

pattern 22:

 If value of cnt1 is 100 or greater, go to next pattern.

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5.4.36. Pattern 23: Trace, Crank Detection After Crossline

Patterns 21 and 22 perform brake operation for 0.1 seconds after detection of the first crossline, allowing the MCU

car to pass the second crossline. Pattern 23 continues the processing after this.

The MCU car is past the crosslines, so the next task is detecting the crank (right-angle turn). The MCU car must

turn immediately as soon as the crank is encountered, so it is proceeding at low speed. In addition, the MCU car

must continue to trace the centre line up to the crank.

We envision the present situation as shown in the following figures:

○○ ○○ ○ ●● ●

→0xf8

(Checking with all 8 sensors)

At a left crank, the state of the eight sensors is 0xf8, as shown in the

figure at left. The software judges a sensor state of 0xf8 as indicating a

left crank.

At this point, the MCU car will drift toward the edge and go off the

track if the steering wheel is not turned all the way to the left. How

many degrees of turn is this? The actual value depends on the physical

characteristics of the individual MCU car, so it is necessary to confirm

how far the steering wheel can turn by looking at the actual car. We will

use a value of about 38 degrees.

To accomplish a sharp left turn, we will use a left motor speed that is

lower and a right motor speed that is higher. As for the actual

percentages, we can’t say for sure until we try it out. For the time being,

we’ll use settings of 10% for the left motor and 50% for the right motor.

The settings can be summarized as follows:

Steering angle: –38 degrees

Left motor: 10%, Right motor: 50%

Afterward, go to pattern 31.

●● ●○ ○ ○○ ○

→0x1f

(Checking with all 8 sensors)

This is a right crank. The basic approach is the same as for a left crank.

The settings can be summarized as follows:

Steering angle: 38 degrees

Left motor: 50%, Right motor: 10%

Afterward, go to pattern 41.

When proceeding straight ahead, the sensor state is 0x00. The software

judges this as meaning that the MCU car is positioned over the centre

line. The steering angle is 0 degrees. The problem is the PWM values

of the motors. The motor PWM values must be such that the MCU car

can negotiate a 90-degree turn when the crank is encountered. For the

time being, we’ll use a setting 40% for both motors. This can be fine

tuned later when doing test runs. The settings can be summarized as

follows:

Steering angle: 0 degrees

Left motor: 40%, Right motor: 40%

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Let’s assume the MCU car has drifted left of centre.

As little by little the MCU car drifts farther left of centre, the four

resulting sensor states are as shown in the figure at left. Additional

sensor states are possible when the MCU car is even farther left of

centre, but we will not add more sensor states because we know that the

section of track following the crosslines will be straight and further

movement to the left is not likely.

Since the MCU car is left of centre, it is necessary to turn the steering

wheel to the right. If the amount of turn is too small and the amount of

drift is large, the MCU car will be unable to return to the centre. If the

amount of turn is too large, it will overshoot the centre and the car will

end up zigzagging right and left. Fine adjusting the angle to precisely

the right value is difficult. For the time being, we will use a setting of 8

degrees. We’ll make the right motor PWM value lower than that of the

left motor since we’re turning to the right. The settings can be

summarized as follows:

Steering angle: 8 degrees

Left motor: 40%, Right motor: 35%

Let’s assume the MCU car has drifted right of centre.

As little by little the MCU car drifts farther right of centre, the four

resulting sensor states are as shown in the figure at left. Additional

sensor states are possible when the MCU car is even farther right of

centre, but we will not add more sensor states because we know that the

section of track following the crosslines will be straight and further

movement to the right is not likely.

Since the MCU car is right of centre, it is necessary to turn the steering

wheel to the left. If the amount of turn is too small and the amount of

drift is large, the MCU car will be unable to return to the centre. If the

amount of turn is too large, it will overshoot the centre and the car will

end up zigzagging right and left. Fine adjusting the angle to precisely

the right value is difficult. For the time being, we will use a setting of -8

degrees. We’ll make the left motor PWM value lower than that of the

right motor since we’re turning to the left. The settings can be

summarized as follows:

Steering angle: –8 degrees

Left motor: 35%, Right motor: 40%

It is important to remember that the all eight sensors are used for crank checking. For other checking, MASK3_3

masking is applied and the two middle sensors are not used.

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The finished program code is as follows:

270 : case 23:

271 : /* Trace, crank detection after cross line */

272 : if( sensor_inp(MASK4_4)==0xf8 ) {

273 : /* Left crank determined -> to left crank clearing processing */

274 : led_out( 0x1 );

275 : handle( -38 );

276 : motor( 10 ,50 );

277 : pattern = 31;

278 : cnt1 = 0;

279 : break;

280 : }

281 : if( sensor_inp(MASK4_4)==0x1f ) {

282 : /* Right crank determined -> to right crank clearing processing */

283 : led_out( 0x2 );

284 : handle( 38 );

285 : motor( 50 ,10 );

286 : pattern = 41;

287 : cnt1 = 0;

288 : break;

289 : }

290 : switch( sensor_inp(MASK3_3) ) {

291 : case 0x00:

292 : /* Center -> straight */

293 : handle( 0 );

294 : motor( 40 ,40 );

295 : break;

296 : case 0x04:

297 : case 0x06:

298 : case 0x07:

299 : case 0x03:

300 : /* Left of center -> turn to right */

301 : handle( 8 );

302 : motor( 40 ,35 );

303 : break;

304 : case 0x20:

305 : case 0x60:

306 : case 0xe0:

307 : case 0xc0:

308 : /* Right of center -> turn to left */

309 : handle( -8 );

310 : motor( 35 ,40 );

311 : break;

312 : }

313 : break;

The program uses if statements to distinguish between left and right cranks. Also, a switch statement is used to

branch to the appropriate case according to the value of sensor_inp(MASK3_3).

The meaning of these consecutive case statements

is: “when 0x04 or 0x06 or 0x07 or 0x03 is the

case.”

The meaning of these consecutive case statements

is: “when 0x20 or 0x60 or 0xe0 or 0xc0 is the

case.”

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5.4.37. Patterns 31 and 32: Clearing from Left Crank

Pattern 23 judges a value of 0xf8 from all eight sensors to indicate a left crank and starts a large turn to the left in

order to clear from the crank.

The following issue arises: How long should the large left turn continue? This portion of the program is dedicated

to patterns 31 and 32.

We envision the situation as shown in the following figures:

The software executes a large turn to left when a sensor state of 0xf8 occurs, but due to the speed at which the

MCU car is travelling it turns gradually rather than sharply. When the sensor value is 0x60, indicating that the car

is back near the centre line, the turn is judged to be finished and control returns to pattern 11.

This can be coded as follows:

case 31:

if( sensor_inp(MASK3_3) == 0x60 ) {

pattern = 11;

}

break;

We tried actually running the MCU car using this program code. What happened was that the moment the sensors

detected the left crank and the sensor state was 0xf8 the steering wheel started turning to the left. We anticipated

that the turn would continue until the sensor state was 0x60, but instead of continuing to turn, it immediately

straightened out again and the MCU car ran straight through the crank and off the track. Since the MCU car moves

too fast for us to see exactly what happened, we tried disconnecting the motors and servo and then slowly moving

the car by hand. Careful observation reveals the sensor states to be as shown in the figures that follow.

Note

When you are unsure exactly how the MCU car is moving,

we recommend disconnecting the motors and pushing it by hand to check.

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1

Sensor state 0xf8 is detected, so turn to the left

with a turn angle of 38 degrees until the sensor

state is 0x60.

2

At the moment the turn starts, the sensor state is

0x60 at the place where the white line changes to

black. (Actually, there are white, grey, and black

areas, but we will consider the grey areas to be

white.) When the software recognizes the sensor

state of 0x60 it passes control to pattern 11.

3

Pattern 11 interprets the sensor state of 0x00 to

mean that the MCU car is centred over the centre

line and proceeds straight ahead at turn angle 0

and motor speed 100%. The MCU car runs

straight off the track.

When we checked the sensors we discovered that the leftmost sensor was not optimally adjusted, and it

erroneously gave a reading of 0 before the second and third sensors from the left. This caused an incorrect value of

0x60 at the change from write to black. This could be corrected by adjusting the leftmost sensor to increase its

sensitivity a small amount. But we don’t want the MCU car to run off the track just because of a small difference

in sensor sensitivity, so we’ll modify the program to correct the problem.

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Come to think of it, a certain amount of time has to pass between when 0xf8 is detected and when the final sensor

state of 0x60 occurs at the detection of the centre line. We can rewrite the code so that after the left crank is

encountered, the motor settings are made and the sensors are ignored for 0.2 seconds. Once the portion of the track

where the colour changes has been passed over, we can reactivate checking of the sensors 0.2 seconds later. We

can illustrate this idea with figures as follows:

4

Sensor state 0xe8 is detected, so turn to the left

with a turn angle of 38 degrees. Then proceed for

0.2 seconds while ignoring the sensors.

5

After 0.2 seconds, check sensors to see if their

value is 0x60.

6

Sensor state is still not 0x60, so continue turning.

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7

Sensor state is now 0x60. Go to pattern 11, normal

tracing.

As figure 5 shows, after 0.2 seconds the sensors are past the place where the white line changes to black. After this,

the MCU car can safely continue turning until the sensor state is 0x60. This should do it. It can be coded as

follows:

315 : case 31:

316 : /* Left crank clearing processing ? wait until stable */

317 : if( cnt1 > 200 ) {

318 : pattern = 32;

319 : cnt1 = 0;

320 : }

321 : break;

322 :

323 : case 32:

324 : /* Left crank clearing processing ? check end of turn */

325 : if( sensor_inp(MASK3_3) == 0x60 ) {

326 : led_out( 0x0 );

327 : pattern = 11;

328 : cnt1 = 0;

329 : }

330 : break;

Line 311 checks if the value of cnt1 is 200 or greater. If it is, that means 0.2 seconds have elapsed, so control

passes to pattern 32. Incidentally, cnt1 is cleared to 0 in line 272 before the jump to pattern 31.

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5.4.38. Patterns 41 and 42: Right Crank Clearing Processing

Pattern 23 judges a value of 0x1F from all eight sensors to indicate a right crank and starts a large turn to the right

in order to clear from the crank.

The following issue arises: How long should the large right turn continue? This portion of the program is

dedicated to patterns 41 and 42.

We envision the situation as shown in the following figures:

The software executes a large turn to right when a sensor state of 0x1f occurs, but due to the speed at which the

MCU car is travelling it turns gradually rather than sharply. When the sensor value is 0x06, indicating that the car

is back near the centre line, the turn is judged to be finished and control returns to pattern 11.

This can be coded as follows:

case 41:

if( sensor_inp(MASK3_3) == 0x06 ) {

pattern = 11;

}

break;

We tried actually running the MCU car using this program code. What happened was that the moment the sensors

detected the right crank and the sensor state was 0x1f the steering wheel started turning to the right. We anticipated

that the turn would continue until the sensor state was 0x06, but instead of continuing to turn, it immediately

straightened out again and the MCU car ran straight through the crank and off the track. Since the MCU car moves

too fast for us to see exactly what happened, we tried disconnecting the motors and servo and then slowly moving

the car by hand. Careful observation reveals the sensor states to be as shown in the figures that follow.

Note

When you are unsure exactly how the MCU car is moving,

we recommend disconnecting the motors and pushing it by hand to check.

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1

Sensor state 0x1f is detected, so turn to the left

with a turn angle of 38 degrees until the sensor

state is 0x06.

2

At the moment the turn starts, the sensor state is

0x06 at the place where the white line changes to

black. (Actually, there are white, grey, and black

areas, but we will consider the grey areas to be

white.) When the software recognizes the sensor

state of 0x06 it passes control to pattern 11.

3

Pattern 11 interprets the sensor state of 0x00 to

mean that the MCU car is centred over the centre

line and proceeds straight ahead at turn angle 0

and motor speed 100%. The MCU car runs

straight off the track.

When we checked the sensors we discovered that the rightmost sensor was not optimally adjusted, and it

erroneously gave a reading of 0 before the second and third sensors from the right. This caused an incorrect value

of 0x06 at the change from write to black. This could be corrected by adjusting the rightmost sensor to increase its

sensitivity a small amount. But we don’t want the MCU car to run off the track just because of a small difference

in sensor sensitivity, so we’ll modify the program to correct the problem.

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Come to think of it, a certain amount of time has to pass between when 0x1f is detected and when the final sensor

state of 0x06 occurs at the detection of the centre line. We can rewrite the code so that after the right crank is

encountered, the motor settings are made and the sensors are ignored for 0.2 seconds. Once the portion of the track

where the colour changes has been passed over, we can reactivate checking of the sensors 0.2 seconds later. We

can illustrate this idea with figures as follows:

4

Sensor state 0x1f is detected, so turn to the right

with a turn angle of 38 degrees. Then proceed for

0.2 seconds while ignoring the sensors.

5

After 0.2 seconds, check sensors to see if their

value is 0x06.

6

Sensor state is still not 0x06, so continue turning.

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7

Sensor state is now 0x06. Go to pattern 11, normal

tracing.

As figure 5 shows, after 0.2 seconds the sensors are past the place where the white line changes to black. After this,

the MCU car can safely continue turning until the sensor state is 0x06. This should do it. It can be coded as

follows:

332 : case 41:

333 : /* Right crank clearing processing ? wait until stable */

334 : if( cnt1 > 200 ) {

335 : pattern = 42;

336 : cnt1 = 0;

337 : }

338 : break;

339 :

340 : case 42:

341 : /* Right crank clearing processing ? check end of turn */

342 : if( sensor_inp(MASK3_3) == 0x06 ) {

343 : led_out( 0x0 );

344 : pattern = 11;

345 : cnt1 = 0;

346 : }

347 : break;

Line 328 checks if the value of cnt1 is 200 or greater. If it is, that means 0.2 seconds have elapsed, so control

passes to pattern 42. Incidentally, cnt1 is cleared to 0 in line 281 before the jump to pattern 41.

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5.4.39. Right Lane Change Outline

Patterns 51 to 54 contain program code related to executing a right lane change. An outline of the processing

involved is provided below:

[1]

The check_rightline function detects a right half line. The MCU car must change to the right lane 500 to

1200 mm ahead, so brake operation is performed. Also, sensor input is ignored up to position [2] to prevent

erroneous sensor detection at the second right half line.

[2]

The MCU car starts to proceed slowly from this point. It advances while tracing the centre line.

[3]

When the centre line ends, the steering wheel turns to the right.

[4]

When a new centre line is detected, line tracing restarts using the new centre line.

In this way, the MCU car manoeuvres right lane change. The specifics of the program code used are described

below.

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5.4.40. Pattern 51: Processing at 1st Right Half Line Detection

Control passes to pattern 51 the moment a right half line is detected. First, the MCU car passes over the right half

lines. The characteristics of the portion of track from the position at which the first right half line is discovered to

the position immediately after the second right half line are shown in the following figure:

[1] First crossline

[2] Normal track

[3] Second crossline

[4] Normal track, proceed slowly while tracing centre line

The track, other than the centre line, changes from white to black to white to black again by the time position [4] is

reached. The program must detect these changes and respond appropriately. That sounds pretty complicated.

Let’s look at this in a different way. The distance from position [1] to position [4] is about 100 mm, allowing some

margin for error. (The precise distance is 70 mm: 20 mm for the first half line + 30 mm of black area + 20 mm for

the second half line = 70 mm.) If the MCU car is positioned roughly over the centre line and continues to move

forward for about 100 mm while we ignore the sensor data, we’ll probably come out roughly on course. The kit

car includes no mechanism for detecting distances, but we can use the timer to interrupt reading of sensor data for

a specified duration. We don’t know how long a duration yet because that will depend on how fast the MCU car is

travelling. For the time being, let’s use a pause duration of 0.1 seconds and do fine tuning later. In addition, we’ll

make the LEDs on the motor drive board light to indicate externally that processing of pattern 51 has started.

To summarize:

 Illuminate LED2. (This differs from the processing of crossline to make it possible to tell them apart.)

 Set steering angle to 0 degrees.

 Set PWM value of right and left motors to 0% to initiate brake operation.

 Wait 0.1 seconds.

 After 0.1 seconds elapse, go to next pattern.

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This is what the program code of pattern 51 must accomplish.

case 51:

/* Processing at 1st right half line detection */

led_out( 0x2 );

handle( 0 );

speed( 0 ,0 );

if( cnt1 > 100 ) {

pattern = 52; /* After 0.1 seconds, to pattern 52 */

}

break;

This is the completed program code. Let’s take a moment to review it. When the value of cnt1 is 100 or greater

(after 100 milliseconds have elapsed), control passes to pattern 52. For this to work as expected, the value of cnt1

must be 0 when pattern 51 starts. For example, if the value of cnt1 is 1000 when control passes to pattern 51, the

value of cnt1 will be judged to be 100 or greater the first time the condition is tested, and control will pass

immediately to pattern 52. Execution of pattern 51 takes place only once (a duration of a few dozen µs) rather than

lasting for 0.1 seconds. We need to add another pattern. Pattern 51 will start brake operation and clear cnt1 to 0,

and pattern 52 will check whether 0.1 seconds have elapsed.

To summarize once again:

Let’s rewrite the program to reflect the above changes.

349 : case 51:

350 : /* Processing at 1st right half line detection */

351 : led_out( 0x2 );

352 : handle( 0 );

353 : motor( 0 ,0 );

354 : pattern = 52;

355 : cnt1 = 0;

356 : break;

357 :

358 : case 52:

359 : /* Read but ignore 2nd time */

360 : if( cnt1 > 100 ){

361 : pattern = 53;

362 : cnt1 = 0;

363 : }

364 : break;

The portion of the program code from detection of the right half line to the start of the trace centre line area is now

complete.

Tasks performed by

pattern 51:

 Illuminate LED2.

 Set steering angle to 0 degrees.

 Set PWM value of right and left motors to 0% to initiate brake operation.

 Go to next pattern.

 Clear cnt1.

Tasks performed by

pattern 52:

 If value of cnt1 is 100 or greater, go to next pattern.

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Hint

When a right half line is detected, one LED (the

bottom one) on the motor drive board lights.

No right half line has been detected if it does not

light.

If right half line detection is not working

properly, try unplugging the motor connectors

and pushing the MCU car forward by hand.

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5.4.41. Pattern 53: Trace after Right Half Line

Patterns 51 and 52 perform brake operation for 0.1 seconds after detection of the first right half line, allowing the

MCU car to pass the second right half line. Pattern 53 continues the processing after this.

The MCU car is past the right half lines, so the next task is detecting the end of the centre line. In addition, the

MCU car must continue to trace the straight section of track that leads to the end of the centre line, so normal trace

operation is necessary.

We envision the present situation as shown in the following figures:

→0x00

(Checking with all 8 sensors)

After the right half line ends, the state of the eight sensors is 0x00, as

shown in the figure at left. When this state is detected, the MCU car

starts turning to the right. For a right turn, we would expect that the

right motor speed should be lower and the left motor speed higher. As

for the actual percentages, these will differ depending on factors such

as the speed of the MCU car, wheel slippage, and the response speed

of the servo. We’ll have to see what happens when we try it out with

the actual MCU car. For the time being, we’ll use following settings,

which can be modified later based on running tests.

Steering angle: 15 degrees

Left motor: 40%, Right motor: 31%

Afterward, go to pattern 54.

When proceeding straight ahead, the sensor state is 0x00. The

software judges a sensor state of 0x00 as indicating straight ahead.

There can be no doubt that the steering angle must be straight forward.

The problem is the PWM values of the motors. The speed associated

with a particular value can only be determined in an actual test run.

The speed must be sufficiently low that the MCU car can negotiate the

turn when the end of the centre line is encountered. For the time being,

we’ll use a setting 40% for both motors. This can be fine tuned later

when doing test runs. The settings can be summarized as follows:

Steering angle: 0 degrees

Left motor: 40%, Right motor: 40%

Let’s assume the MCU car has drifted left of centre. As little by little

the MCU car drifts farther left of centre, the four resulting sensor

states are as shown in the figure at left. Additional sensor states are

possible when the MCU car is even farther left of centre, but we will

not add more sensor states because we know that the section of track

following the right half lines will be straight.

Since the MCU car is left of centre, it is necessary to turn the steering

wheel to the right. If the amount of turn is too small and the amount of

drift is large, the MCU car will be unable to return to the centre. If the

amount of turn is too large, it will overshoot the centre and the car will

end up zigzagging right and left. Fine adjusting the angle to precisely

the right value is difficult. For the time being, we will use a setting of

8 degrees. The settings can be summarized as follows:

Steering angle: 8 degrees

Left motor: 40%, Right motor: 35%

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Let’s assume the MCU car has drifted right of centre. As little by little

the MCU car drifts farther right of centre, the four resulting sensor

states are as shown in the figure at left. Additional sensor states are

possible when the MCU car is even farther right of centre, but we will

not add more sensor states because we know that the section of track

following the right half lines will be straight.

Since the MCU car is right of centre, it is necessary to turn the

steering wheel to the left. If the amount of turn is too small and the

amount of drift is large, the MCU car will be unable to return to the

centre. If the amount of turn is too large, it will overshoot the centre

and the car will end up zigzagging left and right. Fine adjusting the

angle to precisely the right value is difficult. For the time being, we

will use a setting of –8 degrees. The settings can be summarized as

follows:

Steering angle: –8 degrees

Left motor: 35%, Right motor: 40%

It is important to remember that all eight sensors are used for detecting the end of the centre line. For other

checking, MASK3_3 masking is applied and the two middle sensors are not used.

The finished program code is as follows:

366 : case 53:

367 : /* Trace, lane change after right half line detection */

368 : if( sensor_inp(MASK4_4) == 0x00 ) {

369 : handle( 15 );

370 : motor( 40 ,31 );

371 : pattern = 54;

372 : cnt1 = 0;

373 : break;

374 : }

375 : switch( sensor_inp(MASK3_3) ) {

376 : case 0x00:

377 : /* Center -> straight */

378 : handle( 0 );

379 : motor( 40 ,40 );

380 : break;

381 : case 0x04:

382 : case 0x06:

383 : case 0x07:

384 : case 0x03:

385 : /* Left of center -> turn to right */

386 : handle( 8 );

387 : motor( 40 ,35 );

388 : break;

389 : case 0x20:

390 : case 0x60:

391 : case 0xe0:

392 : case 0xc0:

393 : /* Right of center -> turn to left */

394 : handle( -8 );

395 : motor( 35 ,40 );

396 : break;

397 : default:

398 : break;

399 : }

400 : break;

The meaning of these consecutive case statements is:

“when 0x04 or 0x06 or 0x07 or 0x03 is the case.”

The meaning of these consecutive case statements is:

“when 0x20 or 0x60 or 0xe0 or 0xc0 is the case.”

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5.4.42. Pattern 54: Right Lane Change End Check

Pattern 53 determines that a right lane change should start when the eight sensors have a value of 0x00 and turns

to the right with a turn angle of 15 degrees. The question then is how long the turn to the right should continue.

This portion of the program code is designated as pattern 54.

Pattern 54 causes the MCU car to proceed to the new centre line on the right. Once the new centre line is found, it

must trace that centre line. This will complete the processing for the right lane change operation. Now, what sort

of sensor status should be interpreted as the presence of the new centre line?

1

Proceeding while turning. Immediately before

detection of new centre line.

2

Rightmost sensors detect centre line. The sensor

state is 0000 0111.

0

1

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3

Middle sensors detect centre line. The sensor

state is 0011 1100.

At this point the new centre line should be

detected and operation reverts to normal tracing.

We will write the program code so that control

passes to pattern 11, normal tracing, when the

sensor state is 0011 1100, while checking with

all eight sensors.

This is the resulting code, based on this thinking:

402 : case 54:

403 : /* Right lane change end check */

404 : if( sensor_inp( MASK4_4 ) == 0x3c ) {

405 : led_out( 0x0 );

406 : pattern = 11;

407 : cnt1 = 0;

408 : }

409 : break;

An LED was illuminated when the right half line was detected, so after turning off the LED in line 405 control is

passed to pattern 11. The situation after 0x3c is detected and control returns to pattern 11 is shown below. The

MCU car is travelling at a rightward angle when it encounters the centre line, so processing by pattern 11 brings it

back to the centre of the track.

0

1

0

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5.4.43. Left Lane Change Outline

Patterns 61 to 64 contain program code related to executing a left lane change. An outline of the processing

involved is provided below:

[1]

The check_leftline function detects a left half line. The MCU car must change to the left lane 500 to 1200

mm ahead, so brake operation is performed. Also, sensor input is ignored up to position 2 to prevent

erroneous sensor detection at the second left half line.

[2]

The MCU car starts to proceed slowly from this point. It advances while tracing the centre line.

[3]

When the centre line ends, the steering wheel turns to the left.

[4]

When a new centre line is detected, line-tracing restarts using the new centre line.

In this way, the MCU car manoeuvres right lane change. The specifics of the program code used are described

below.

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5.4.44. Processing at 1st Left Half Line Detection

Control passes to pattern 61 the moment a left half line is detected. First, the MCU car passes over the left half

lines. The characteristics of the portion of track from the position at which the first left half line is discovered to

the position immediately after the second left half line are shown in the following figure: