nRF52 (XIAO BLE)

The BTHome component supports nRF52840 boards using the Zephyr RTOS framework. This is ideal for ultra-low-power battery-operated sensors.

Supported Boards

Seeed XIAO BLE (nRF52840) - Primary supported board
Other nRF52840 boards (may require board definition adjustments)

Basic Configuration

esphome:
  name: bthome-nrf52
  friendly_name: BTHome nRF52

nrf52:
  board: xiao_ble
  bootloader: adafruit

logger:

external_components:
  - source:
      type: git
      url: https://github.com/dz0ny/esphome-bthome
      ref: main
    components: [bthome]

Pin Naming

nRF52 uses numeric pin references, not GPIO names:

Silkscreen	Pin Number	Function
D0	0	Digital I/O
D1	1	Digital I/O
D2	2	Digital I/O
D3	3	Digital I/O
D4	4	I2C SDA
D5	5	I2C SCL
D6-D10	6-10	Digital I/O

# Correct for nRF52
i2c:
  sda: 4  # D4
  scl: 5  # D5

# NOT like ESP32
# sda: GPIO4  # Wrong!

TX Power Levels

nRF52 supports a wide range of transmit power levels:

Setting	Description
-40	Ultra low power
-20	Very low power
-16	Low power
-12	Low power
-8	Below default
-4	Below default
0	Default
2, 3, 4	Above default
5, 6, 7, 8	High power

bthome:
  tx_power: 4  # Good balance of range and power

Complete Example

Door sensor with battery monitoring:

esphome:
  name: door-sensor
  friendly_name: Door Sensor

nrf52:
  board: xiao_ble
  bootloader: adafruit

logger:

external_components:
  - source:
      type: git
      url: https://github.com/dz0ny/esphome-bthome
      ref: main
    components: [bthome]

# Battery monitoring
sensor:
  - platform: adc
    pin: 29  # VBAT/2 on XIAO BLE
    id: battery_voltage
    name: "Battery Voltage"
    update_interval: 60s
    filters:
      - multiply: 2.0

  - platform: template
    id: battery_percent
    name: "Battery"
    unit_of_measurement: "%"
    lambda: |-
      float voltage = id(battery_voltage).state;
      float percent = (voltage - 3.0) / (4.2 - 3.0) * 100.0;
      if (percent > 100) percent = 100;
      if (percent < 0) percent = 0;
      return percent;
    update_interval: 60s

# Door contact
binary_sensor:
  - platform: gpio
    pin:
      number: 3
      mode: INPUT_PULLUP
    id: door_contact
    name: "Door"
    device_class: door

# BTHome configuration
bthome:
  min_interval: 5s
  max_interval: 10s
  tx_power: 4
  sensors:
    - type: battery
      id: battery_percent
  binary_sensors:
    - type: door
      id: door_contact
      advertise_immediately: true

Deep Sleep

For maximum battery life, enable deep sleep:

deep_sleep:
  run_duration: 15s
  sleep_duration: 5min
  wakeup_pin:
    number: 3
    mode: INPUT_PULLUP
    inverted: true  # Wake on LOW (door open)

With deep sleep:

Device wakes every 5 minutes to send sensor updates
Door opening immediately wakes the device
Battery can last months to years

Bootloader Options

XIAO BLE supports several bootloaders:

nrf52:
  board: xiao_ble
  bootloader: adafruit  # Default, UF2 upload support

Bootloader	Description
`adafruit`	Default, supports UF2 drag-and-drop
`adafruit_nrf52_sd132`	With SoftDevice S132
`adafruit_nrf52_sd140_v6`	With SoftDevice S140 v6

Flashing

UF2 Method (Recommended)

Double-tap the reset button to enter bootloader mode
A USB drive named “XIAO-SENSE” or “NICENANO” will appear
Copy the .uf2 file to the drive
Device will automatically reset and run

The firmware is at:

.esphome/build/<device-name>/.pioenvs/<device-name>/zephyr.uf2

DFU Method

Use the .zip file for over-the-air updates:

.esphome/build/<device-name>/.pioenvs/<device-name>/firmware.zip

Power Consumption

The nRF52840 is optimized for ultra-low power:

Mode	Current
Active (advertising)	~5-15mA
Deep sleep	~2-5µA
BLE TX (0 dBm)	~5mA
BLE TX (8 dBm)	~15mA

With a 400mAh battery and 5-minute sleep intervals, expect 6-12 months of battery life.

Troubleshooting

Build fails with “tinycrypt not found”

Ensure you’re using the latest component version. The component automatically enables tinycrypt for encryption support.

Pins not working

Use numeric pin references, not GPIO names:

# Correct
pin: 4

# Wrong
pin: GPIO4

Device not appearing in bootloader mode

Make sure the USB cable supports data (not charge-only)
Double-tap reset quickly (within 0.5s)
Try a different USB port