LD2410B-P Module

That matters because the B's pads are the hard part of the B. They sit at a fine pitch, about half of breadboard spacing, and a heavy tip bridges them in a second. The B-P moves that job to the factory, so your first hour goes on wiring and tuning rather than rework.

What stays the same as the B:

• Motion and near-still presence up to 5m, with 0.75m distance gates.
• A 3.3V UART at 256000 baud, supported by ESPHome's ld2410 component.
• An OUT pin that reads high while someone is present.
• Bluetooth for the HLKRadarTool app, including tuning after the case is shut.
• A 5V DC supply.

What changes:

• Height. The pins add depth behind the board, so leave room in a slim case.
• Pitch. Pins soldered to the B's pads keep the B's spacing. They mate with fine-pitch sockets or the supplied wires, not with a 2.54mm breadboard.

The B-P sits between the two: slimmer than the C, and ready to wire unlike the bare B. For small runs of the same sensor, that is often the fastest path from parts to working units, and the pins give every board the same, repeatable connection.

1. B-P 5V to the C3 board's 5V pin (the USB rail).
2. GND to GND.
3. B-P TX to GPIO4, used as the C3's UART RX.
4. B-P RX to GPIO5, used as the C3's UART TX.
5. OUT to GPIO3 if you want a hardware presence line.

Avoid the C3's strapping pins, GPIO2, GPIO8 and GPIO9, for the radar. A 3.3V high on one of those at boot can stop the board from starting. GPIO4 and GPIO5 are clear of that on common dev boards.

uart:
  rx_pin: GPIO4
  tx_pin: GPIO5
  baud_rate: 256000
  parity: NONE
  stop_bits: 1

ld2410:

binary_sensor:
  - platform: ld2410
    has_target:
      name: Presence
    has_moving_target:
      name: Movement

switch:
  - platform: ld2410
    bluetooth:
      name: Radar Bluetooth

The switch lets you turn the B-P's Bluetooth off from Home Assistant once tuning is done, and back on when you want the app again. The full YAML with thresholds and distances is on the ESPHome page, and pins for the classic ESP32, D1 Mini and Arduino are on the wiring page.

If presence never arrives, open the ESPHome logs first. No frames at all points at crossed or loose serial wires; frames with no presence usually point at thresholds.

Check your own board's pin map before wiring. C3 boards differ in which pins they break out, and a pin label on one board is not always the same GPIO on another.

• Face the antenna side at the room. The patches along the strip do the work; the back of the board should face the wall.
• Keep plastic thin and flat in front. A thin, even wall over the antenna works; thick or ribbed plastic scatters the signal.
• Keep metal out of the beam. Screws, foil labels and metal backboxes in front of the antenna blind or confuse it.
• Give the pins somewhere to go. Route them and their wires behind the board, not across its face.
• Separate it from other radios. A Wi-Fi board pressed flat against the antenna adds noise; a small gap helps.

Then re-tune in place. Close the case, mount it where it will live, and open HLKRadarTool:

1. Leave the room and watch the per-gate energy for a minute.
2. Raise the thresholds on any gate that stays lit with no one there.
3. Cap the farthest gate at your far wall.
4. Lengthen the no-one delay if presence drops while you sit still.

Printable cases and notes on adding a light sensor are on the LD2410 case page, and how far each gate reaches is on range and field of view.

Use the single to settle the design questions that only a real board answers: whether your case leaves room for the pins, where the antenna sits, and which thresholds your rooms need. Once one unit holds presence cleanly through a quiet evening, the rest are copies.

Write down the settings that worked: farthest gates, per-gate thresholds and the no-one delay. Each new B-P ships with factory defaults, and copying a known-good set over Bluetooth or from ESPHome takes minutes instead of another evening of tuning.

How the B-P compares with nearby choices:

• LD2410B: the bare board. Thinnest install, but you solder.
• LD2410C: same radar and Bluetooth with a 2.54mm header for breadboards.
• LD2410B test kit: a B with the parts to connect it to a laptop straight away.
• AKAMATIS v2.2: a B already built into a finished Wi-Fi sensor.

Match these to your build first:

• You want pins fitted, not bare pads.
• Your case has the depth for the pins and wires.
• You have fine-pitch jumpers or plan to use the 5-pack's wires.

The B versus C choice, laid out in full, is on LD2410B vs LD2410C.