Documentation

// HLK-LD2450 reader for Arduino Mega
// Connect radar TX -> Mega RX1 (pin 19), RX -> Mega TX1 (pin 18)
// Frame: AA FF 03 00 [T1 8B][T2 8B][T3 8B] 55 CC  (30 bytes total)

uint8_t buf[64];
int idx = 0;

int16_t decode(uint8_t lo, uint8_t hi) {
  // Sign bit is the high bit of the high byte; value is the rest
  int16_t v = (int16_t)(((uint16_t)hi << 8) | lo) & 0x7FFF;
  return (hi & 0x80) ? v : -v;
}

void setup() {
  Serial.begin(115200);
  Serial1.begin(256000);
  Serial.println("LD2450 ready");
}

void loop() {
  while (Serial1.available()) {
    uint8_t b = Serial1.read();
    buf[idx++] = b;

    if (idx >= 30) {
      if (buf[0] == 0xAA && buf[1] == 0xFF &&
          buf[28] == 0x55 && buf[29] == 0xCC) {
        for (int t = 0; t < 3; t++) {
          int o = 4 + t * 8;
          int16_t x = decode(buf[o + 0], buf[o + 1]);
          int16_t y = decode(buf[o + 2], buf[o + 3]);
          int16_t spd = decode(buf[o + 4], buf[o + 5]);
          uint16_t dist = buf[o + 6] | (buf[o + 7] << 8);
          if (x || y || dist) {
            Serial.print("T"); Serial.print(t + 1);
            Serial.print(" x="); Serial.print(x);
            Serial.print("mm y="); Serial.print(y);
            Serial.print("mm spd="); Serial.print(spd);
            Serial.print("cm/s dist="); Serial.println(dist);
          }
        }
        Serial.println();
        idx = 0;
      } else {
        // Slide window by one byte to re-sync
        memmove(buf, buf + 1, idx - 1);
        idx--;
      }
    }
    if (idx >= (int)sizeof(buf)) idx = 0;
  }
}

// HLK-LD2450 on ESP32 - 3-target position reader
#include <HardwareSerial.h>
HardwareSerial Radar(2);

uint8_t buf[64];
int idx = 0;

int16_t decode(uint8_t lo, uint8_t hi) {
  int16_t v = (int16_t)(((uint16_t)hi << 8) | lo) & 0x7FFF;
  return (hi & 0x80) ? v : -v;
}

void setup() {
  Serial.begin(115200);
  Radar.begin(256000, SERIAL_8N1, 16, 17);
  Serial.println("LD2450 ESP32 reader ready");
}

void loop() {
  while (Radar.available()) {
    buf[idx++] = Radar.read();
    if (idx >= 30) {
      if (buf[0] == 0xAA && buf[1] == 0xFF &&
          buf[28] == 0x55 && buf[29] == 0xCC) {
        for (int t = 0; t < 3; t++) {
          int o = 4 + t * 8;
          int16_t x = decode(buf[o], buf[o + 1]);
          int16_t y = decode(buf[o + 2], buf[o + 3]);
          int16_t spd = decode(buf[o + 4], buf[o + 5]);
          uint16_t dist = buf[o + 6] | (buf[o + 7] << 8);
          if (x || y || dist) {
            Serial.printf("T%d  x=%d mm  y=%d mm  spd=%d cm/s  dist=%u\n",
                          t + 1, x, y, spd, dist);
          }
        }
        idx = 0;
      } else {
        memmove(buf, buf + 1, idx - 1);
        idx--;
      }
    }
    if (idx >= (int)sizeof(buf)) idx = 0;
  }
}

#!/usr/bin/env python3
"""HLK-LD2450 reader for Raspberry Pi - prints up to 3 tracked targets."""
import serial, time

PORT = "/dev/serial0"
BAUD = 256000

HEADER = b"\xAA\xFF\x03\x00"
FOOTER = b"\x55\xCC"
FRAME_LEN = 30

def decode_signed(lo, hi):
    v = ((hi << 8) | lo) & 0x7FFF
    return v if (hi & 0x80) else -v

ser = serial.Serial(PORT, BAUD, timeout=0.5)
print("LD2450 Pi reader started")

buf = bytearray()
while True:
    buf += ser.read(64)
    while True:
        i = buf.find(HEADER)
        if i < 0 or len(buf) - i < FRAME_LEN:
            break
        frame = buf[i:i + FRAME_LEN]
        if frame[-2:] != FOOTER:
            buf = buf[i + 1:]
            continue
        for t in range(3):
            o = 4 + t * 8
            x   = decode_signed(frame[o + 0], frame[o + 1])
            y   = decode_signed(frame[o + 2], frame[o + 3])
            spd = decode_signed(frame[o + 4], frame[o + 5])
            dist = frame[o + 6] | (frame[o + 7] << 8)
            if x or y or dist:
                print(f"T{t + 1}  x={x:5} mm  y={y:5} mm  "
                      f"spd={spd:4} cm/s  dist={dist}")
        buf = buf[i + FRAME_LEN:]
    time.sleep(0.02)

# HLK-LD2450 on Raspberry Pi Pico (MicroPython)
from machine import UART, Pin
import time

uart = UART(0, baudrate=256000, tx=Pin(0), rx=Pin(1))
buf = bytearray()
HEADER = b"\xAA\xFF\x03\x00"
FOOTER = b"\x55\xCC"
FRAME_LEN = 30

def decode_signed(lo, hi):
    v = ((hi << 8) | lo) & 0x7FFF
    return v if (hi & 0x80) else -v

print("LD2450 Pico reader ready")

while True:
    if uart.any():
        buf += uart.read(uart.any())
    while True:
        i = buf.find(HEADER)
        if i < 0 or len(buf) - i < FRAME_LEN:
            break
        frame = buf[i:i + FRAME_LEN]
        if frame[-2:] != FOOTER:
            buf = buf[i + 1:]
            continue
        for t in range(3):
            o = 4 + t * 8
            x   = decode_signed(frame[o], frame[o + 1])
            y   = decode_signed(frame[o + 2], frame[o + 3])
            spd = decode_signed(frame[o + 4], frame[o + 5])
            dist = frame[o + 6] | (frame[o + 7] << 8)
            if x or y or dist:
                print("T%d x=%d y=%d spd=%d dist=%d" % (t + 1, x, y, spd, dist))
        buf = buf[i + FRAME_LEN:]
    time.sleep_ms(20)