Explanations of how lidar communication works

[eleimt]

Hello.

I'm trying to use this LiDAR LD19 in my project, but I can't figure out how to interpret the data it sends.

I connected it to a TTL adapter:

1. White -> RX
2. Yellow -> TX
3. Black -> GND
4. Red -> 5V

If I just connect it, nothing happens. I found that to start scanning, I need to send 4 bytes: "0xAA, 0x55, 0xF0, 0x0F". (I don’t know if there is a command to stop it — please let me know if there is.)

Here’s my Go code:

package main

import (
    "fmt"
    "time"
    
    "github.com/tarm/serial"
)

func main() {
    config := &serial.Config{
        Name: "COM4",
        Baud: 230400,
    }
    
    port, err := serial.OpenPort(config)
    if err != nil {
        panic(err)
    }
    defer port.Close()
    
    // Command to send
    cmd := []byte{0xAA, 0x55, 0xF0, 0x0F}
    
    // Send command
    written, err := port.Write(cmd)
    if err != nil || written != len(cmd) {
        panic("Error sending command")
    }
    
    fmt.Printf("Command sent (%d bytes): % X\n", written, cmd)
    
    time.Sleep(1 * time.Second)
    
    response := make([]byte, 15000)
    
    for {
        n, err := port.Read(response)
        if err != nil && n == 0 {
            fmt.Println("No response from device")
            return
        }
        
        // Output formatted HEX
        fmt.Printf("Response (%d bytes): % X\n", n, response[:n])
        
        time.Sleep(100 * time.Millisecond)
    }
}

And here’s what I’m receiving:

Command sent (4 bytes): AA 55 F0 0F
Response (26 bytes): A5 5A 50 07 01 00 00 00 00 00 00 A9 FE FE FE FE FE FE FE FE FE FE FE FE FE FE
Response (0 bytes):
Response (1103 bytes): FA FA A5 5A 14 00 E3 02 01 43 4F 49 4E 2D 44 34 00 00 00 00 00 00 00 00 00 00 00 00 01 A5 5A 00 00 80 01 81 AA 55 00 19 CB 6F 77 76 87 55 50 03 00 2C 2B 0A 38 57 0A 74 8F 0A 88 9B 0A 14 B3 0A 60 C6 0A AC C1 0A 68 B1 0A 68 9D 0A 78 8D 0A 88 81 0A 98 79 0A 98 75 0A 84 6D 0A 90 65 0A A4 4D 0A A8 41 0A AC 3D 0A D4 35 0A E8 29 0A 14 22 0A B8 A5 0A A8 CE 0A F4 E6 0A AA 55 00 19 BF 76 5F 7D 56 4E C0 CA 0A CC BA 0A 78 AA 0A 3C 96 0A 8C 81 0A 40 02 00 34 93 03 6C 97 03 8C 9F 03 A0 A3 03 A4 A7 03 A0 AF 03 A0 B3 03 A0 BB 03 A0 D3 03 6C E3 03 98 FB 03 AC FB 03 6C 93 03 50 6F 03 6C 5F 03 94 5B 03 A8 5B 03 B0 5B 03 AC 5F 03 AA 55 00 19 A5 7D 51 84 54 B2 A4 6B 03 68 7B 03 68 B3 03 8C DF 03 A0 FB 03 AC 13 04 BC 27 04 B0 2B 04 A8 2F 04 9C 3F 04 A0 4B 04 A8 5F 04 A8 67 04 A8 73 04 A8 83 04 A8 9B 04 8C A7 04 38 AF 04 9C AA 04 DC C1 04 B4 01 00 2C B2 07 80 E6 07 AC 1A 08 B0 52 08 AA 55 00 19 99 84 43 8B C2 4A BC 8E 08 28 DF 08 78 0F 09 90 1F 09 A4 27 09 A0 27 09 9C 2B 09 A0 2F 09 A0 3B 09 A0 3B 09 A4 43 09 A0 4B 09 9C 53 09 90 5B 09 7C 63 09 6C 63 09 70 73 09 58 7F 09 64 8F 09 6C A3 09 68 AF 09 5C BF 09 58 C3 09 5C CB 09 50 D3 09 AA 55 00 0F 8B 8B 43 B3 D9 6B 50 DB 09 50 E7 09 48 F7 09 08 13 0A 18 5F 0A 38 73 0A 2C 77 0A 2C 77 0A 24 1B 0A 40 0F 0A 48 0B 0A 44 0B 0A 48 0B 0A 34 03 0A 24 03 0A AA 55 69 01 89 B3 89 B3 10 5D 2C FF 09 AA 55 00 19 CF B3 63 06 BD F3 30 EF 09 2C F3 09 2C 03 0A 48 13 0A 54 0B 0A 50 FF 09 48 E3 09 40 D3 09 40 D3 09 3C DB 09 40 EB 09 4C FB 09 64 07 0A 60 DF 09 4C CF 09 70 E7 09 8C DF 09 78 DB 09 7C DB 09 78 DF 09 78 E7 09 78 DB 09 6C CB 09 64 DF 09 70 07 0A AA 55 00 19 A7 06 71 0D CB 43 70 03 0A 64 03 0A 6C 07 0A 70 07 0A 70 FF 09 70 FB 09 88 F3 09 8C EF 09 80 EF 09 78 F3 09 64 F7 09 64 07 0A 68 23 0A 58 37 0A 38 5F 0A 10 BF 0A CC D2 0A 64 3A 0A 8C C6 09 E0 86 09 E8 56 09 24 27 09 38 F7 08 F0 1E 08 4C E7 07 AA 55 00 19 B9 0D 65 14 B6 52 70 CF 07 78 BB 07 8C AF 07 94 AB 07 90 A3 07 A0 9B 07 9C 97 07 A0 9B 07 98 9B 07 8C A3 07 90 A7 07 9C B7 07 98 C3 07 98 D3 07 94 D7 07 8C E7 07 88 F7 07 74 0B 08 58 27 08 D0 3A 08 30 39 08 B8 01 00 30 72 34 2C 46 34 9C 01 00 AA 55 00 19 AD 14 31 1B AB 42 98 4A 18 7C CA 17 70 56 17 C8 3A 17 04 3B 17 0C 4B 17 C4 52 17 58 62 17 30 E2 17 24 4E 18 58 5A 18 88 8A 18 7C 01 00 00 E6 35 04 E2 35 F4 CD 35 00 DE 35 FC C1 35 00 B6 35 B8 A9 35 88 99 34 84 09 35 F0 B5 35 E8 B9 35 04 CD 35 AA 55 00 19 77 1B 13 22 2C 69 34 9D 35 E8 F4 35 D0 00 00 F0 FC 11 F8 C4 11 F8 3C 11 F0 40 11 00 CD 10 14 91 10 08 4D 10 00 D1 0F 08 C5 0F 10 91 0F 14 19 0F 1C 09 0F 1C D9 0E 1C B1 0E 40 5D 0E F0 F9 0D D8 11 13 F8 5E 13 70 67 13 88 4F 13 94 3F 13 60 43 13 AA 55 00 19 5B 22 05 29 9C 5C EC 19 13 80 02 00 38 AF 09 54 63 09 50 13 09 54 C7 08 58 8B 08 70 57 08 64 17 08 E4 B2 07 84 B5 07 14 29 07 F8 3C 06 14 F9 05 28 F1 05 20 BD 05 2C AD 05 28 85 05 84 4A 05 34 5B 05 DC 76 05 60 E3 05 8C E7 05 A8 DF 05 B0 D7 05 AA 55 00 19 4B 29 FD 2F 3C 4F A8 BB 05 A8 9F 05 A8 8F 05 A4 73 05 A8 5B 05 A8 3B 05 40 37 05 AC 36 05 28 3E 05 B4 41 05 68 21 05 D8 CE 04 E0 D9 04 98 D1 04 6C D5 04 5C 09 05 34 25 05 2C 2D 05 1C 55 05 08 55 05 00 71 05 14 7D 05 28 91 05 08 8D 05 14 6D 05 AA 55 00 19 43 30 ED 36 71 4C 10 85 05 08 75 05 00 B5 05 F4 88 05 F8 DC 05 F0 A8 05 EC D4 05 FC C8 05 08 01 06 20 E1 05 2C E9 05 38 1D 06 58 11 06 60 1D 06 5C 1D 06 84 45 06 90 59 06 A0 6D 06
Response (1360 bytes): D4 71 06 38 72 06 48 83 06 A0 7B 06 A4 73 06 8C 4B 06 78 2B 06 AA 55 00 19 35 37 AF 3D 95 45 78 17 06 80 03 06 64 EF 05 2C DB 05 74 F3 05 70 EF 05 74 F7 05 50 E3 05 9C 8E 05 68 7A 05 34 1E 05 F0 79 05 6C 35 05 4C 21 05 98 5D 05 F4 99 05 0C A2 05 F0 85 05 D4 65 05 88 1D 05 68 01 05 58 05 05 38 F1 03 2C CD 03 1C DD 03 AA 55 00 19 F5 3D 89 44 42 34 14 69 03 20 69 02 08 99 02 E8 78 02 04 6D 02 F0 8C 02 F8 0C 02 E4 6C 02 FC 24 02 04 09 02 E0 28 02 E4 4C 02 D0 5C 02 EC 28 02 E4 FC 01 04 31 02 E4 5C 02 F8 E8 01 EC D8 01 EC 20 02 E4 08 02 E4 20 02 C8 E8 01 CC 28 02 A4 00 00 AA 55 00 19 CF 44 99 4B B8 41 B4 00 00 B4 00 00 C4 0C 02 D4 14 02 D8 FC 01 B4 00 00 C8 18 02 C8 44 02 CC 20 02 BC 00 00 D8 14 02 E8 2C 02 F0 C8 01 F4 A8 01 1C CD 01 F0 A4 01 F0 C0 01 00 B5 01 F0 0C 02 DC AC 01 DC 14 02 F4 8C 01 DC 6C 01 D8 B4 01 E4 B8 01 AA 55 00 19 E1 4B 8B 52 01 57 D8 AC 01 00 05 02 08 D5 01 FC 8C 01 1C C5 01 5C 95 01 B0 7D 01 98 89 01 A8 89 01 08 82 01 2C 86 01 48 86 01 74 8E 01 84 92 01 6C 8A 01 88 8A 01 70 86 01 74 86 01 84 92 01 54 86 01 64 86 01 64 8E 01 50 8E 01 54 8A 01 50 8E 01 AA 55 00 19 D3 52 3D 59 3B 46 54 8A 01 50 8E 01 48 8E 01 50 92 01 40 8A 01 40 8E 01 3C 8E 01 30 96 01 64 92 01 90 9A 01 A8 9E 01 CC 9A 01 E0 A6 01 F8 A6 01 14 A7 01 2C AF 01 34 B3 01 40 B3 01 4C BB 01 4C B7 01 54 BF 01 5C BF 01 70 CB 01 74 CF 01 7C D3 01 AA 55 00 19 83 59 0B 60 65 74 80 CF 01 88 D7 01 90 DB 01 90 DB 01 98 E3 01 9C E3 01 94 E7 01 9C E7 01 A0 E7 01 A0 EF 01 A8 F3 01 A8 F7 01 A8 F3 01 B8 F7 01 B8 F7 01 BC F3 01 BC F7 01 B4 F3 01 AC F3 01 A8 F3 01 A8 EF 01 A0 EB 01 A0 E3 01 9C DF 01 98 DF 01 AA 55 00 19 51 60 DF 66 5E 4B 9C D7 01 9C D7 01 94 D7 01 80 CF 01 78 CB 01 50 CB 01 30 CF 01 04 C7 01 A0 BA 01 4C 9E 01 48 9A 01 28 9A 01 38 92 01 14 86 01 28 8A 01 20 86 01 24 7E 01 28 8A 01 1C 7E 01 34 8E 01 34 82 01 3C 7E 01 58 7A 01 5C 72 01 50 7E 01 AA 55 00 19 25 67 AD 6D 22 47 4C 7E 01 3C 72 01 3C 7A 01 20 76 01 E4 7D 01 B8 6D 01 BC 6D 01 78 6D 01 5C 95 01 34 8D 01 28 89 01 24 95 01 28 81 01 2C BD 01 20 B5 01 18 99 01 14 B5 01 20 7D 01 F0 84 01 E4 AC 01 E4 C4 01 DC B0 01 DC AC 01 D8 B8 01 E0 D4 01 AA 55 00 19 F1 6D 7D 74 7F 57 C8 80 01 E0 C8 01 E4 BC 01 00 85 01 C4 A8 01 CC B4 01 D0 9C 01 CC D4 01 DC E0 01 00 BD 01 EC A8 01 E4 AC 01 E4 A4 01 E4 14 02 D0 B4 01 E0 E0 01 D4 00 02 D0 E4 01 CC E8 01 D0 D8 01 D4 CC 01 EC FC 01 EC 04 02 EC B0 01 34 B9 01 AA 55 00 19 C3 74 07 7B 22 42 F0 B8 01 14 ED 01 14 C9 01 F8 FC 01 14 C5 01 FC 10 02 08 BD 01 04 E1 01 FC C8 01 F4 20 02 F8 00 02 30 C5 01 1C 05 02 F0 B4 01 F8 10 02 F8 14 02 24 31 02 24 1D 02 F8 14 02 04 19 02 F0 0C 02 F0 24 02 EC E0 01 D8 4C 02 C8 58 02 AA 55 00 19 4B 7B B9 81 41 B3 DC C8 02 F4 D8 02 04 11 04 28 69 04 4C 9D 04 80 9D 04 C8 B5 04 18 D6 04 64 DE 04 AC EA 04 F0 06 05 1C 0B 05 40 1B 05 64 27 05 78 2F 05 8C 3B 05 94 47 05 9C 47 05 A4 53 05 A8 5F 05 AC 63 05 A8 6B 05 B0 77 05 AC 7B 05 A0 5B 05 AA 55 00 19 FD 81 95 88 DD 41 AC 37 05 B4 2B 05 BC 2F 05 B8 33 05 AC 37 05 B0 43 05 B4 53 05 B0 5F 05 B4 6F 05 98 37 05 AC EB 04 BC E3 04 C4 DB 04 C8 DB 04 C4 D3 04 C0 CF 04 C0 D3 04 C4 CF 04 BC CB 04 B4 C7 04 B0 BF 04 B8 C3 04 C4 C3 04 C0 BF 04 B4 BF 04 AA 55 00 19 D9 88 41 8F B4 4F BC BB 04 AC BB 04 AC BF 04 BC B7 04 8C B7 04 8C BF 04 8C BF 04 8C B7 04 94 B3 04 9C B3 04 A0 B3 04 9C B3 04 A0 B7 04 A0 B3 04 90 B3 04 94 BB 04 80 C7 04 00 D3 04 74 EA 04 F0 05 05 94 71 05 84 71 05 4C 69 05 44 5D 05 30 51 05 AA 55 00 19 73 8F D9 95 AD 56 44 4D 05 BC F5 04 84 ED 04 F4 28 05 E4 28 05 F0 48 05 F0 50 05 CC 68 05 20 02 00 4C B3 08 44 DF 08 58 1B 09 58 4B 09 50 6F 09 58 9B 09 58 C7 09 4C EB 09 48 1F 0A 38 4B 0A 54 87 0A 88 93 0A 50 A7 0A B8 CA 0A 00 D2 0A 80 C1 0A AA 55 00 19 1D 96 87 9C CF 46 5C A9 0A 6C 9D 0A 74 9D 0A 94 85 0A 9C 75 0A 88 65 0A 84 59 0A A0 51 0A A0 49 0A A8 45 0A B8 39 0A D0 2D 0A D4 29 0A 0C 22 0A B4 95 0A A8 CE 0A 08 EB 0A C4 C6 0A D8 BA 0A 94 B2 0A 58 A6 0A C4 89 0A 88 01 00 0C 97 03 50 93 03 AA 55 00 19 CB 9C 33 A3 C1 70 7C 9B 03 98 9F 03 A0 A7 03 A0 A7 03 9C B3 03 A8 BB 03 A8 C7 03 8C D7 03 78 F3 03 A0 FB 03 AC F3 03 60 83 03 4C 6B 03 74 67 03 94 5B 03 AC 63 03 B0 63 03 B0 63 03

Also, I found documentation (link ), which says that each data packet starts with 0x54. However, the packet sizes vary.

Could you please help me understand how to correctly parse and convert these packets according to the documentation , and what kind of human-readable data I should expect to get?

Let me know if you'd like help interpreting the documentation or writing a parser for the data format.

[DArtagnant]

Hello,
I'm Dartagnant and I will try to help you.

If you want to use the lidar connected to a computer, I recommend you to use the TTL adapter that comes with the lidar.
There is also a Windows application that is useful to see on screen the points found by the lidar and thus allows you to know if the lidar is working correctly.

Once I have said this, let's start debugging!

Communication Interface

Lidar LD19 does not support incoming commands from the microcontroller apart from the speed, as a matter of fact it has no RX port.
Instead, please refer to this section of my documentation which explains how to communicate with the lidar.

You should send a PWM instead of a serial communication or if you don't need to manually control the speed just connect this pin to the ground.
The lidar will then automatically start working.

Data Protocol

This part of my documentation explains step by step how to decode data incoming from the lidar, which indeed starts with 0x54, even with 0x54 0x2C.

The packet sizes are actually constant but in your actual code I think you rely on the delay to separate each packet which produces inconsistent results. The correct way to parse lidar data is explained in the link above.

(in line if err != nil && n == 0 { don't you mean if err != nil || n == 0 { ?)

End

I think you will find the answers to your other questions by reading carefully this documentation.

I don't program in Go, though I can guess the meaning of your code I wouldn't be able to write a parser in this language yet.
However, you can find a working parser in C++ here and a brand-new Rust one here.

Let me know if you have any other questions and if I should modify some unclear parts of the documentation.
Out of curiosity, do you use Lidar LD19 for the RoboCup competition?