ESP32 LD2410 Wiring: ESP32-C3, D1 Mini, ESP8266 and Arduino

1. Sensor VCC to the ESP32's 5V or VIN pin.
2. Sensor GND to any GND pin.
3. Sensor TX to GPIO16, which is RX2.
4. Sensor RX to GPIO17, which is TX2.
5. Optional: sensor OUT to a spare GPIO such as GPIO18 for a hardware presence line.

The sensor's TX and OUT pins swing to 3.3V, which the ESP32 reads directly, and the ESP32's 3.3V TX is what the sensor's RX expects. No level shifter needed. On an LD2410C the pin order from pin 1 is TX, RX, OUT, GND, VCC; the original and B boards start with OUT instead, so read the pinout for your version.

Keep the jumpers short, especially the 5V pair. A USB port that sags under an ESP32's Wi-Fi bursts plus the radar shows up as brownout resets. A decent 1A USB supply fixes it.

For firmware, ESPHome's built-in component is the quickest route to Home Assistant. The ESPHome YAML walkthrough uses exactly these pins, so the config drops in unchanged.

GPIO20 (RX) and GPIO21 (TX) are the usual choice. On a Seeed XIAO ESP32-C3 they are labelled D7 and D6, and the board's 5V pad carries USB power for the sensor. The C3 can route a UART to other free GPIOs too, but steer clear of its strapping pins, GPIO2, GPIO8 and GPIO9.

uart:
  id: ld2410_uart
  rx_pin: GPIO20
  tx_pin: GPIO21
  baud_rate: 256000
  parity: NONE
  stop_bits: 1

• Sensor TX to GPIO20 (D7 on the XIAO).
• Sensor RX to GPIO21 (D6 on the XIAO).
• VCC to 5V, GND to GND.

Seeed also makes a 24GHz mmWave board sized for its XIAO line, built on an LD2410-family radar. If you would rather not assemble anything, the AKAMATIS v2.2 is a finished version of the same idea: an LD2410B wired to a Seeed ESP32-C3 with an external Wi-Fi antenna, in a case, running ESPHome.

A XIAO plus an LD2410C fits in a very small printed box. The enclosure guide covers the clearance the radar needs in front of it.

One C3 caveat: if you enable the logger on a hardware UART instead of USB, it can collide with the pins you picked for the sensor. Leave logging on USB and the conflict never appears.

In ESPHome, set the logger's baud_rate to 0 so it stops writing to the serial port. Then put the UART on GPIO1 (TX) and GPIO3 (RX), the pins marked TX and RX on a Wemos D1 Mini. Logs still reach you over Wi-Fi.

• Sensor TX to the D1 Mini's RX pin (GPIO3).
• Sensor RX to its TX pin (GPIO1).
• VCC to the D1 Mini's 5V pin, GND to G.
• Unplug the sensor's TX wire before flashing over USB, or the upload fails.

There is a second option: the ESP8266 can swap UART0 onto GPIO15 (TX) and GPIO13 (RX), marked D8 and D7 on the D1 Mini. That keeps the USB pins clear for flashing. Software serial is the option to skip; bit-banged serial on an ESP8266 is unreliable at 256000 baud.

The ESP8266 has less memory and a single core, so leave engineering mode off in daily use. For a new build, an ESP32-C3 board costs about the same and removes the UART juggling entirely.

#include <ld2410.h>

ld2410 radar;

void setup() {
  Serial.begin(115200);
  Serial2.begin(256000, SERIAL_8N1, 16, 17);
  radar.begin(Serial2);
}

void loop() {
  radar.read();
  if (radar.presenceDetected()) {
    Serial.println(radar.stationaryTargetDistance());
  }
}

The pattern is the same in any library: open a hardware serial port at 256000, hand it to the parser, and call its read function often. Libraries differ in naming and in which configuration commands they support, so check the examples that ship with the version you install.

• Call the read function every loop; frames arrive many times a second.
• Use the moving and stationary flags separately if lights and heating need different logic.
• Write settings once, then leave them; the module stores them.

Configuration commands let your sketch set the maximum gates, the timeout and per-gate sensitivity. Setting them in the phone app or PC tool first is often faster.

Print what the library reports to the serial monitor before you write any automation logic. Walk away from the sensor and back again, then sit still for a minute. If the stationary flag drops while you sit, raise the sensitivity of the gate you sit in or move the sensor closer; the numbers you see here are the same energy values the configuration tools show.

A two-resistor divider is enough: 1kΩ from the Uno's TX pin to the sensor RX, and 2kΩ from the sensor RX to ground. That brings 5V down to about 3.3V. A small bidirectional level-shifter board does the same job and tidies the wiring.

• The Uno's only hardware port also carries USB, so use it for the sensor only if you give up the serial monitor.
• SoftwareSerial will not keep up at 256000; set the module to 57600 or lower with the configuration tool before connecting.
• Or skip the serial side and read the OUT pin with digitalRead.

That last option is the simplest Arduino LD2410 project of all. Configure range and timeout once over Bluetooth, then treat OUT as a presence switch.

Whichever board you use, tie the grounds together first and connect the data lines second. That order spares the sensor's pins from stray current while you plug things in.