Li DAR Scanner Protocol Guide

User Manual:

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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 00 4F 00 61 AD 00 47 79 00 40 72 42 3C 05 6D 37 05 8A 3A 05 93 34 05 9C
35 05 AD 35 05 B8 35 05 C6 35 05 D5 34 05 E5 36 05 F2 31 06 07 2D 06 16 2E
06 2B 2E 06 40 36 06 52 35 06 67 32 06 61 2D 06 45 2B 06 22 2B 06 03 31 05
DF 30 05 C6 DC 27
Breakdown:
AA ： Start Byte
00 4F：Frame Size = 0x004F = 79 bytes (not including the CRC)
00 ： Protocol Version
61 ： Frame Type
AD： Payload Type
00 47：Payload Size = 0x0047 = 71 bytes
79 ：Rotation Speed = (0x79 => 121) x 0.05r/s = 6.05r/s
00 40：Angle Offset = (0x40 => 64) * 0.01° = 0.64°
72 42：Starting Angle = (0x7242 => 29250) * 0.01° = 292.5°
3C： Sample ID #1
05 6D： Distance Measurement #1 = (0x056D => 1389) * 0.25mm = 347.25mm
37： Sample ID #2
05 8A： Distance Measurement #2 = (0x058A => 1418) *0.25mm = 354.5mm
........
30: Sample ID #22
05 C6: Distance Measurement #22 = (0x05C6 => 1478) * 0.25mm = 369.5mm
DC 27：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: Start Byte
00 09：Frame Size = 0x0009 = 9 Bytes (not including the CRC)
00：Protocol Version
61：Frame Type
AE: Payload Type
00 01: Payload Size = 0x0001 = 1 byte
C9：Payload: Rotation Speed = (0xC9 = 201) * 0.05r/s = 10.05r/s
02 2C: CRC 0x022c
Version 1.0

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