A tiny, coin-cell-powered Matter over Thread smart home button built on the HolyIoT 25008 and HolyIoT 25015 Bluetooth beacon boards. Both boards use the Nordic nRF54l15 SoC — a chip capable of running Matter and Zigbee, making it perfect for a DIY wireless smart home button.
This project was built for a YouTube build video. See the full step-by-step on my YouTube channel
No soldering required. Flash the precompiled binary, commission it to your smart home, and you're done.
| Item | Notes |
|---|---|
| HolyIoT 25008 | Core board — button only |
| HolyIoT 25015 | Adds SHT40 temperature & humidity sensor |
| Seeed Studio Xiao RP2040 | Used as a CMSIS-DAP programmer. via picoprobe firmware. Any Raspberry PI pico board with the RP2040 or RP2350 will do |
| PCB spring-pin test clip | Clamps to the board's SWD pads — no soldering needed. 4 Pins. 1.5MM Pitch |
| CR2032 coin cell battery | Powers the finished button |
The 25015 is a drop-in hardware upgrade over the 25008. It uses the same firmware but additionally reports temperature and humidity to your smart home hub. Both boards run off a single coin cell.
Start here. You do not need to install the nRF Connect SDK or compile anything.
Four precompiled binaries are provided in the Releases section:
| File | Board | Mode |
|---|---|---|
micro_matter_button_h25008_om1.hex |
HolyIoT 25008 | Mode 1 — Dimmable switch (requires binding) |
micro_matter_button_h25008_om2.hex |
HolyIoT 25008 | Mode 2 — Generic switch |
micro_matter_button_h25015_om1.hex |
HolyIoT 25015 | Mode 1 — Dimmable switch (requires binding) |
micro_matter_button_h25015_om2.hex |
HolyIoT 25015 | Mode 2 — Generic switch |
Not sure which mode to pick? Read the Operating Modes section below, then come back.
The HolyIoT boards have no USB port. You flash them over SWD using a Raspberry Pi Pico running picoprobe firmware.
-
Hold the BOOTSEL button on the Pico and plug it into your computer.
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Download the picoprobe UF2 and drag it onto the Pico — it will appear as a USB drive.
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Wire the Pico to the HolyIoT board's SWD pads through the PCB test clip:
Pico Pin HolyIoT Pad GP2 (SWCLK) SWCLK GP3 (SWDIO) SWDIO GND GND 3V3 VCC (optional — or use the coin cell)
Install pyocd and its nRF54l pack:
pip install pyocdFlash the firmware (replace the filename with your chosen binary):
pyocd load ./holyiot_25008_mode1.hex -t nrf54lThat's it — the chip will reset and start advertising over Bluetooth LE.
Open your smart home app and add a new Matter device. Use the QR code or manual pairing code below when prompted.
Manual pairing code: 34970112332
QR Code: Scan or screenshot this
The LED on the board will blink slowly while waiting for commissioning and turn off once paired.
Two firmware operating modes are available. Choose at flash time — no recompilation needed, just pick the right binary.
⚠️ This mode requires Matter binding to work. After commissioning, you must bind the button to a light using your smart home hub. Without a binding, button presses are silently ignored. See Setting Up Binding below.
This mode acts as a Dimmable Light Switch (Matter Light Switch device type). Commands are sent directly to bound lights over the Thread network.
| Gesture | Action |
|---|---|
| Short press (< 400 ms) | Toggle the bound light on/off |
| Long press (hold > 500 ms) | Cycle brightness from 0% → 100% while held |
| Double-tap (two presses within 400 ms) | Wake the accelerometer and enter rotational dimming mode |
| Rotate while in dimming mode | Adjust brightness proportionally to the rotation angle |
| Tilt horizontally | Exit dimming mode and lock current brightness |
Rotational dimming activates for up to 10 seconds after a double-tap. If no movement is detected for 3 seconds during dimming, the accelerometer powers back down automatically to save battery.
Best used with: Home Assistant, or any Matter hub that supports binding.
✅ No binding required. This mode works out of the box with Apple Home, Google Home, Amazon Alexa, Home Assistant, and any other Matter-certified platform.
This mode exposes a Generic Switch (Matter Generic Switch device type) on endpoint 2. Your smart home platform receives the button events and you configure what happens via automations.
| Gesture | Matter Event |
|---|---|
| Short press | ShortRelease |
| Long press (hold > 500 ms) | LongPress → LongRelease on release |
Use your platform's automation builder to trigger any action — turn on a light, run a scene, send a notification, or anything else your hub supports.
Works with: Apple Home, Google Home, Amazon Alexa, Home Assistant, Samsung SmartThings, and any Matter-compatible hub.
Binding is a Matter concept that tells the switch which light(s) to control. Without it, the button has no target to send commands to.
Home Assistant makes binding straightforward, especially when running on a VM or alongside a Thread Border Router. I have a dedicated video on my YouTube channel walking through how to share Matter devices across fabrics and set up bindings in Home Assistant — watch it here.
If you prefer the command line, use chip-tool to write the binding table.
Average current consumption is approximately 6 µA — achieved by:
- Running as a Thread Sleepy End Device (SED) with long poll intervals
- Powering down the LIS2DH12 accelerometer at boot (Mode 2) or on demand (Mode 1)
- Keeping all debug/serial peripherals disabled in the production build
- Link-time optimisation (LTO) enabled
A standard CR2032 (≈220 mAh capacity) gives a rough estimate of ~36,000 hours / ~4 years of theoretical runtime. Real-world life will be lower due to battery self-discharge and voltage droop, but multi-year life off a single coin cell is realistic.
STL files for the 3D printed case are available in the assets/stl/ directory. The design is two parts that screw together — the board sits in the base and the top half has a flexible plunger that transmits button presses through the face of the case. Prints cleanly in PLA with no post-processing.
Two versions are provided:
micro_matter_button_25008.stl- Holyiot 25008micro_matter_button_25015.stl- Holyiot 25015programming_jig.stl- Jig to hold the Holyiot Board during programming
The 25015 uses the same firmware binaries but adds two extra sensors:
- SHT40 — temperature and humidity (fully working, reported every 5 minutes after commissioning)
- LPS22HB — barometric pressure (not yet implemented — the driver in NCS assumes I²C; the board uses SPI. The sensor is explicitly powered down at boot.)
The 25015 case has a small airflow hole near the sensor for accurate readings.
For developers who want to customise the firmware.
- nRF Connect SDK v3.x (v3.2.4 used for the precompiled binaries)
- West build tools
The operating mode is a Kconfig choice. Pass it on the west build command line:
# Mode 1 — Dimmable switch
west build -b holyiot_25008_nrf54l15_cpuapp -- -DCONFIG_MATTER_BUTTON_MODE_1=y
# Mode 2 — Generic switch
west build -b holyiot_25008_nrf54l15_cpuapp -- -DCONFIG_MATTER_BUTTON_MODE_2=yReplace holyiot_25008 with holyiot_25015 for the sensor variant.
| Option | Default | Description |
|---|---|---|
MATTER_BUTTON_MODE_1 |
y | Dimmable switch with accelerometer-based rotational dimming |
MATTER_BUTTON_MODE_2 |
n | Generic switch with short-press and long-press events |
Both options are mutually exclusive — only one may be set at a time.
Hold the button for 12 seconds. The LED will blink white as a warning. Release before 15 seconds to cancel. After 15 seconds the device resets and re-enters commissioning mode.
Source code is licensed under the LicenseRef-Nordic-5-Clause licence, consistent with the nRF Connect SDK samples this project is based on.
Built and documented for the YouTube channel. Full build guide and video linked below.