Li DAR Scanner Protocol Guide

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Delta2B 360˚ 2D LiDAR Scanner - Protocol Guide
1. Protocol Guide
The LiDAR Scanner uses UART (3.3V TTL @ Baud Rate: 230400) to communicate with
external devices. The communication is unidirectional from the LiDAR to the external device.
The host device does not need to acknowledge transmissions. All data is transmitted in Hex.
The guide will explain how to extract distance measurement data and device health information
from the received data.

2. Frame Structure
Each transmission follows this frame structure:

Start Byte

Frame
Size

Protocol
Version

Frame
Type

Payload
Type

Payload
Size

Payload

Checksum

Index

Notes

Start Byte

0

1 byte, Fixed to 0xAA

Frame Size

1-2

2 bytes, Size of the frame in bytes from the Start Byte to the end
of the Payload. Does not include Checksum.
MSB first

Protocol Version

3

1 byte, Fixed to 0x00

Frame Type

4

1 byte, Fixed to 0x61

Payload Type

5

1 byte, To differentiate between different payload types. See
table below

Payload Size

6-7

2 bytes, Size of the frame payload
MSB first

Version 1.0

Payload

8-n

n bytes, Frame payload

Checksum

n+1 n+2

2 bytes, MSB first

2.1. Payload Types
Payload Type

Payload Identifier

Payload Length

Note

Distance
Measurement

0xAD

(3N+5) bytes

where N is number of
samples

Device Error

0xAE

1 unsigned byte

Payload represents
rotation speed with
0.05r/s resolution

2.1.1 Distance Measurement
Transmission of distance measurement data from scanner.
Payload Identifier:
0xAD
Payload Length:
(3N+5) bytes where N is number of samples
Payload Scheme:
Byte

Description

Byte 0

1 byte, unsigned - Rotation speed - resolution 0.05r/s

Bytes 1 - 2

2 bytes, signed - MSB first - Angle offset - resolution 0.01˚

Bytes 3 - 4

2 bytes, unsigned - MSB first - Starting angle for the frame - resolution 0.01˚

Byte 5

1 byte, unsigned - Sample ID - Can be discarded

Byte 6 - 7

2 bytes, unsigned - MSB First - Distance value for first sample

Byte 8

1 byte, unsigned - Sample ID - Can be discarded

Byte 9 - 10

2 bytes, unsigned - MSB First - Distance value for second sample

...

Repeat for N samples

Version 1.0

2.1.1.1 Calculating the Angle for Nth Distance Measurement
Angle for nth sample = Starting angle + 22.5˚(n-1)/N
Where:
N = Number of distance samples = (length of payload - 5)/3
Each frame carries the distance measurements for a 22.5˚ sweep.

2.1.2 Device Error
Indicates a device error - rotation speed is too low to perform measurements
Payload Identifier:
0xAE
Payload Length:
1 byte
Payload:
Unsigned byte - Rotation speed with 0.05r/s resolution

3. Checksum Calculation
The checksum is a 16-bit number, created by adding up all of the bytes from the frame. The
checksum calculation is a standard CRC-16 checksum.
The following is an demonstration of the checksum calculation in C:
u16 ​CRC16​(u8 *Start_Byte,u16 Num_Bytes)
{
u16 Checksum = ​0​;
while​ (Num_Bytes--)
{
// CRC
Checksum += *Start_Byte++;
}
return​ Checksum;
}

Version 1.0

4. Example
4.1 Example 1 - Distance Measurement
Frame:
AA
35
06
DF

00
05
2B
30

4F
AD
2E
05

00
35
06
C6

61
05
40
DC

AD 00 47 79 00 40 72 42 3C 05 6D 37 05 8A 3A 05 93 34 05 9C
B8 35 05 C6 35 05 D5 34 05 E5 36 05 F2 31 06 07 2D 06 16 2E
36 06 52 35 06 67 32 06 61 2D 06 45 2B 06 22 2B 06 03 31 05
27

Breakdown:
AA ：
00 4F：
00 ：
61 ：
AD：
00 47：
79 ：
00 40：
72 42：
3C：
05 6D：
37：
05 8A：
........
30:
05 C6:
DC 27：

Start Byte
Frame Size = 0x004F = 79 bytes (not including the CRC)
Protocol Version
Frame Type
Payload Type
Payload Size = 0x0047 = 71 bytes
Rotation Speed = (0x79 => 121) x 0.05r/s = 6.05r/s
Angle Offset = (0x40 => 64) * 0.01° = 0.64°
Starting Angle = (0x7242 => 29250) * 0.01° = 292.5°
Sample ID #1
Distance Measurement #1 = (0x056D => 1389) * 0.25mm = 347.25mm
Sample ID #2
Distance Measurement #2 = (0x058A => 1418) *0.25mm = 354.5mm
Sample ID #22
Distance Measurement #22 = (0x05C6 => 1478) * 0.25mm = 369.5mm
CRC 0xDC27

4.2 Example 2 - Device Error
Frame:
AA 00 09 00 61 AE 00 01 69 02 2C

Version 1.0

Breakdown:
AA:
00 09：
00：
61：
AE:
00 01:
C9：
02 2C:

Start Byte
Frame Size = 0x0009 = 9 Bytes (not including the CRC)
Protocol Version
Frame Type
Payload Type
Payload Size = 0x0001 = 1 byte
Payload: Rotation Speed = (0xC9 = 201) * 0.05r/s = 10.05r/s
CRC 0x022c

Version 1.0
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