HLK-LD2410B with ESP32: Wiring, UART Test and Presence Detection

What LD2410B measures

LD2410B is a 24 GHz radar for moving/still-target presence applications. Its public integration reports target state, distance and energy information. It is not a heart-rate, ECG or diagnostic sensor. Bluetooth is used for configuration, while a microcontroller can use UART or the digital OUT signal. Keep its antenna face unobstructed and away from moving fans for the first test.

Power and wiring for ESP32-C3

Read the printed labels rather than assuming left-to-right connector order. Hi-Link specifies 5 V power and 3.3 V output logic. The radar draws roughly 80 mA in the manufacturer specification; choose a stable supply with margin. Do not accidentally connect 5 V to a GPIO.

Select a hardware UART

Install Arduino-ESP32 and select an ESP32-C3 profile with USB CDC enabled for the monitor. This sketch uses UART1 at the LD2410B default 256000 baud, 8N1; the computer monitor stays at 115200. If the module was previously reconfigured, use its saved UART baud rate instead of assuming the default. GPIO4/5/6 are this example’s C3 wiring, not universal pins for every ESP32 board.

Upload a non-destructive communications check

#include <Arduino.h>
HardwareSerial radar(1);
constexpr int RADAR_RX = 4;  // radar TX -> ESP32-C3 GPIO4
constexpr int RADAR_TX = 5;  // ESP32-C3 GPIO5 -> radar RX
constexpr int RADAR_OUT = 6;
uint32_t bytesSeen = 0;
uint32_t lastReport = 0;
void setup() {
  Serial.begin(115200);  // USB CDC
  radar.begin(256000, SERIAL_8N1, RADAR_RX, RADAR_TX);
  pinMode(RADAR_OUT, INPUT);
}
void loop() {
  while (radar.available()) {
    radar.read();  // Binary frames; count bytes without interpreting them
    ++bytesSeen;
  }
  if (millis() - lastReport >= 1000) {
    Serial.printf("UART bytes/s=%lu | OUT=%d\n",
                  (unsigned long)bytesSeen, digitalRead(RADAR_OUT));
    bytesSeen = 0;
    lastReport = millis();
  }
  delay(1);
}

This program counts received bytes and reads OUT; it does not change radar settings or parse distance/energy frames. A nonzero count confirms data is reaching the selected UART, not that every frame is valid.

Interpret the first results

Walk into and out of the sensing area while observing OUT and the UART byte count. After its configured absence delay, OUT should return to the module’s configured away state. Do not use the first reading as a fixed room occupancy verdict: sensitivity, gates, mounting and nearby movement affect it. Record the original thresholds before adjusting one setting at a time.

Connect to Home Assistant through ESPHome

For decoded moving/still states, follow the ESPHome ld2410 component linked below. Configure the hardware UART at the same baud, add the ld2410: hub and its has_target, has_moving_target or has_still_target entities. Use unused board pins and keep the logger off that radar UART. This article’s Arduino check and an ESPHome application are alternative firmware; upload one at a time.

Troubleshoot without over-tuning

Downloads, references and validation

Download the minimal Arduino sketch (.zip)

• Hi-Link LD2410B product and downloads
• ESPHome LD2410 component
• Espressif HardwareSerial API

Reviewed 21 October 2026. The downloadable minimal sketch was compiled using Arduino-ESP32 3.3.0 with the board profile recorded in its README. This checks software compilation; wiring, sensor readings and supplied hardware have not been bench-tested.

Compatible product and related tutorials

• HLK-LD2410B 24GHz Human Presence Radar Sensor with Bluetooth and UART

Browse all product tutorials · Ask ESP32S support