Documentation

#include <SoftwareSerial.h>

// HLK-2410B TX -> D2, RX -> D3
SoftwareSerial radar(2, 3);

String line;

void setup() {
  Serial.begin(115200);
  radar.begin(115200);
  Serial.println("HLK-2410B ready");
}

void loop() {
  while (radar.available()) {
    char c = radar.read();
    if (c == '\n' || c == '\r') {
      if (line.length() > 0) {
        line.trim();
        // Sensor emits ASCII status: "ON" when presence detected, "OFF" otherwise
        if (line.indexOf("ON") >= 0) {
          Serial.println("[PRESENCE] occupied");
        } else if (line.indexOf("OFF") >= 0) {
          Serial.println("[PRESENCE] vacant");
        } else {
          Serial.print("[RAW] ");
          Serial.println(line);
        }
        line = "";
      }
    } else {
      line += c;
    }
  }
}

#include <HardwareSerial.h>

HardwareSerial radar(2);  // UART2

#define RXD2 16
#define TXD2 17

bool present = false;

void setup() {
  Serial.begin(115200);
  radar.begin(115200, SERIAL_8N1, RXD2, TXD2);
  Serial.println("HLK-2410B on ESP32 UART2");
}

void loop() {
  static String buf;
  while (radar.available()) {
    char c = radar.read();
    if (c == '\n' || c == '\r') {
      if (buf.length()) {
        buf.trim();
        bool nowPresent = (buf.indexOf("ON") >= 0);
        if (nowPresent != present) {
          present = nowPresent;
          Serial.printf("Presence -> %s\n", present ? "OCCUPIED" : "VACANT");
        }
        buf = "";
      }
    } else {
      buf += c;
    }
  }
}

import serial
import time

ser = serial.Serial('/dev/serial0', 115200, timeout=1)
present = None

print("HLK-2410B reader started. Ctrl-C to exit.")
try:
    while True:
        line = ser.readline().decode(errors='ignore').strip()
        if not line:
            continue
        now = "ON" in line
        if now != present:
            present = now
            print("Presence:", "OCCUPIED" if present else "VACANT")
        else:
            # Optional raw print for debugging
            # print("raw:", line)
            pass
except KeyboardInterrupt:
    ser.close()

from machine import UART, Pin
import time

uart = UART(0, baudrate=115200, tx=Pin(0), rx=Pin(1))
buf = ""
present = None

print("HLK-2410B on Pico UART0")

while True:
    if uart.any():
        chunk = uart.read()
        if chunk:
            buf += chunk.decode('utf-8', 'ignore')
            while '\n' in buf or '\r' in buf:
                # split on either line ending
                idx = min([i for i in (buf.find('\n'), buf.find('\r')) if i >= 0])
                line, buf = buf[:idx].strip(), buf[idx+1:]
                if line:
                    now = ("ON" in line)
                    if now != present:
                        present = now
                        print("Presence:", "OCCUPIED" if present else "VACANT")
    time.sleep_ms(50)