Zigbee Smart Clock

Modulino™ Thermo

MAX7219 32x8 display

Modulino™ Light

Nano Connector Carrier

Qwiic Cables Bundle

Arduino Nano Matter

Arduino IDE

<html><body>This project will guide you in building your own Zigbee powered smart clock. The clock features a 32×8 LED matrix display, automatic clock synchronization, temperature and humidity measurements, ambient light sensing, automatic brightness control, and multiple clock faces. The clock can also be controlled remotely through Zigbee using Home Assistant. <figure><img src="https://projects.arduinocontent.cc/60ab5267-b9f2-4674-b15b-31dc08dbd234.jpg"/><figcaption></figcaption></figure><a href="https://en.wikipedia.org/wiki/Zigbee">Zigbee </a>is a popular home automation mesh network used by various smart home devices like lightbulbs, sensors and actuators. The Arduino Nano Matter recently received support for Zigbee in addition to Matter and Bluetooth Low Energy. This project's goal is to showcase the capabilities of the <a href="https://github.com/SiliconLabsSoftware/arduino/tree/main/libraries/Zigbee">Zigbee library </a>on the Nano Matter. I developed this project in parallel with the development of Zigbee support for Silicon Labs boards, with the goal of testing more complex, real-world applications of the library. <h3>Features</h3><ol><li>32x8 LED matrix display </li><li>Automatic clock synchronization over Zigbee </li><li>Temperature and humidity measurement </li><li>Ambient light level measurement </li><li>Automatic display brightness (with auto display off in darkness) </li><li>Multiple available clock faces </li><li>Sensor readings and display control over Zigbee with Home Assistant </li></ol> This project builds on my previous smart clock project <a href="https://gitlab.com/bozont91/smartclock">auraSmartClock </a>- which is a WiFi smart clock built on the ESP8266. Most of the graphics libraries and clock faces were re-used from this project. <h3>Hardware</h3>The project includes a 3D printable base plate to neatly organize the components. It has mounting holes for the Connector Carrier, both Modulinos and the display - all using the same M3x10 screws and bolts. The base is optional, the clock can be assembled without it. <figure><img src="https://projects.arduinocontent.cc/bdb9eff2-8dc1-4acd-be5b-a1540b6414bb.png"/><figcaption></figcaption></figure>You can find the STL files for 3D printing <a href="https://github.com/bozont/auraZigbee/tree/main/stl">here. </a><h3>Hardware assembly</h3>The wiring diagram for the project looks like this: <figure><img src="https://projects.arduinocontent.cc/8654bc6c-178b-48b1-8482-204ee790465c.png"/><figcaption></figcaption></figure> Connecting the hardware components is straightforward: <ol><li>If you're using the 3D printed base, fix your connector carrier and Modulino boards to the base plate using M3x10 screws and bolts (you can use the screws and bolts from the <a href="https://store.arduino.cc/products/plug-and-make-kit">Plug and Make </a>kit, they're exactly the size needed) </li><li>Insert your Nano Matter board into the Connector Carrier - make sure the USB port's orientation is correct </li><li>Use the QWIIC connector on the carrier to connect the Modulino boards (they can be in any order) - if you're not using the Connector Carrier, use A4 for SDA and A5 for SCL </li><li>If you're using the 3D printed base, remove the leftmost and rightmost LED module from your MAX7219 display and use the holes underneath (on the display's PCB) to fix the screen to the base (use the same M3x10 screws and bolts) - then re-attach the removed LED modules </li><li>Connect the display's SPI and power pins to the Nano Matter's power and SPI pins as seen on the wiring diagram above </li></ol> <figure><img src="https://projects.arduinocontent.cc/99230952-c0e1-40f4-9bc9-e8d4f32c855e.jpg"/><figcaption>The assembled hardware on the 3D printed baseboard</figcaption></figure> <h3>Firmware</h3>You can get the firmware sketch from the following GitHub repository: <a href="https://github.com/bozont/auraZigbee/">https://github.com/bozont/auraZigbee/ </a>Alternatively, you can download a ZIP file with the firmware here: <a href="https://github.com/bozont/auraZigbee/archive/refs/heads/main.zip">https://github.com/bozont/auraZigbee/archive/refs/heads/main.zip </a>Make sure you have version 5.0.0 of the Silicon Labs Arduino Core installed. If you had the core installed previously, make sure it's updated to 5.0.0 where Zigbee support was introduced. <figure><img src="https://projects.arduinocontent.cc/592f396f-7e8a-4ca2-9dd4-7878baf0ab6b.png"/><figcaption></figcaption></figure> Before getting started, install the following libraries which are needed by the project: <ol><li>Arduino_Modulino (0.9.0 - Arduino - https://github.com/arduino-libraries/Arduino_Modulino) </li><li>bozontlabsUptime (1.0.0 - Tamas Jozsi - https://github.com/bozont/bozontlabsUptime) </li><li>bozontlabsMAX7219 (1.0.1 - Tamas Jozsi - https://github.com/bozont/bozontlabsMAX7219) </li><li>millisRTC (1.0.2 - Tamas Jozsi - https://github.com/bozont/millisRTC) </li></ol>After the libraries have been installed: <ol><li>Open the project's sketch in the Arduino IDE </li><li>Select the Arduino Nano Matter as your board </li><li>Select OpenOCD as the programmer under Tools &gt; Programmer. </li><li>Burn the bootloader from the top menu with Tools &gt; Burn Bootloader. This resets the board to a clean state for the Zigbee firmware. It's recommended to do this when switching between protocols. </li><li>Select the Zigbee protocol stack at the top menu from Tools &gt; Protocol stack &gt; Zigbee </li><figure><img src="https://projects.arduinocontent.cc/89547b64-a0d5-415a-ae4e-37b28eab8420.png"/><figcaption></figcaption></figure><li>Build and flash the project </li></ol><ol><li>The clock should now start up and be ready for Zigbee pairing </li></ol> <figure><img src="https://projects.arduinocontent.cc/e4bd1acb-82bd-419c-94f6-df00ec05c110.jpg"/><figcaption>The device in Zigbee pairing mode after flashing</figcaption></figure> <ol><li>After successful flashing you'll see messages in the Serial Monitor like this: </li></ol><pre>Thu 1970-01-01 00:00:00 (I) auraSmartClock Zigbee Edition (tm) </pre><pre>Thu 1970-01-01 00:00:00 (I) Build date: Sep 7 2026 15:43:07 </pre><pre>Thu 1970-01-01 00:00:00 (I) Initializing sensors... </pre><pre>Thu 1970-01-01 00:00:00 (I) Modulino Thermo initialized successfully </pre><pre>Thu 1970-01-01 00:00:00 (I) Modulino Light initialized successfully </pre><pre>Thu 1970-01-01 00:00:00 (I) Initializing display... </pre><pre>Thu 1970-01-01 00:00:00 (I) Display initialized </pre><pre>Thu 1970-01-01 00:00:00 (I) Light level: 450.00 lx | Average light level: 450.00 lx | Display brightness: 2 </pre><pre>Thu 1970-01-01 00:00:00 (I) Temperature: 28.2 C </pre><pre>Thu 1970-01-01 00:00:00 (I) Humidity: 27.0% </pre><pre>Thu 1970-01-01 00:00:00 (I) Device is unpaired and entered network pairing mode </pre><pre>Thu 1970-01-01 00:00:00 (I) Connecting to Zigbee network... </pre><h3>Software architecture</h3>If you'd like to dive deeper into how the software on the clock works I suggest checking out the <a href="https://github.com/bozont/auraZigbee">GitHub repository </a>of the project. The main file is <a href="https://github.com/bozont/auraZigbee/blob/main/auraZigbee.ino">auraZigbee.ino </a>with the familiar <code class="code">begin() </code>and <code class="code">loop() </code>functions. All the subsystem functionalities of the clock (like display, sensor and Zigbee handling) are organized into separate files with singleton classes under the <a href="https://github.com/bozont/auraZigbee/tree/main/src">src/ </a>folder. The begin() function initializes all the peripherals and Zigbee through the subsystem classes. In loop() you can find a simple cooperative scheduling for all the subsystem tasks. Fun software fact: The Nano Matter does not have a built-in RTC, so the software uses millis() to keep the clock running. While this is not as accurate as a hardware RTC, the clock is synchronized with the Zigbee coordinator every hour. Any inaccuracies picked up during an hour are disappearing after a sync. <h3>Zigbee pairing</h3>The device is now ready to be paired to a Zigbee hub/coordinator. For this example we're using Home Assistant with ZHA (Zigbee Home Automation). The device should also work with other Zigbee ecosystems that support the required functionality, including Zigbee time synchronization. If you have Home Assistant installed, but don't yet have a Zigbee network, you can use any of the supported Silicon Labs Zigbee boards as a USB Zigbee stick. For setting up your board as a Zigbee dongle see instructions <a href="https://github.com/SiliconLabsSoftware/arduino/blob/main/extra/firmware/readme.md">here. </a>To start pairing, go to the Zigbee settings in Home Assistant and click the Add device button. The device should be discovered within a few seconds and paired with Home Assistant. <figure><img src="https://projects.arduinocontent.cc/2acb9330-ff1a-4f49-8df6-194fc4c0fa65.png"/><figcaption>Home Assistant searching for new Zigbee devices</figcaption></figure> <figure><img src="https://projects.arduinocontent.cc/304603e4-e503-44ca-afa1-0de3ec413b3a.png"/><figcaption>Home Assistant successfully found and paired the device</figcaption></figure>After pairing, the device automatically requests the current time and timezone from the Zigbee coordinator and updates its clock accordingly. <pre>Thu 1970-01-01 00:00:00 (I) Connecting to Zigbee network... </pre><pre>Thu 1970-01-01 00:00:00 (I) Connected to Zigbee network; PAN_ID='0x2cde' channel='20' </pre><pre>Thu 1970-01-01 00:01:50 (I) Requesting Zigbee time sync... </pre><pre>Thu 1970-01-01 00:01:50 (I) Temperature: 27.8 C </pre><pre>Thu 1970-01-01 00:01:51 (I) Uptime: 0d 0h 1m 51s </pre><pre>Thu 1970-01-01 00:01:51 (W) No time sync response received; checking again in 1 seconds... </pre><pre>Thu 1970-01-01 00:01:52 (I) Zigbee time sync response received </pre><pre>Mon 2026-09-07 15:46:57 (I) Current NTP time: 1788796017 </pre><pre>Mon 2026-09-07 15:46:57 (I) Current date and time: 2026-09-07 15:46:57 </pre><pre>Mon 2026-09-07 15:46:57 (I) Zigbee time sync finished </pre>The time and timezone information is provided by the Zigbee coordinator - the clock will sync and show the time and timezone provided by the coordinator, there's no manual setup step for the time. If you're having offset issues, please check the time and timezone settings on your coordinator. Pairing only needs to be done the first time using the device - the Nano will remember the network information even after restarting or being powered off. The device's sensor readings are now available through Zigbee in Home Assistant - also, the screen can be switched on/off remotely. <figure><img src="https://projects.arduinocontent.cc/87b938d4-2a90-4272-aeba-d88dd175c6c5.png"/><figcaption>The device paired to Home Assistant</figcaption></figure>After pairing the device will show the current time and measured temperature: <figure><img src="https://projects.arduinocontent.cc/d02dfa11-27ba-486d-8cb3-a2435dd188ce.jpg"/><figcaption>The device automatically synchronizes its clock after pairing - or after reboot</figcaption></figure> <h3>Clock faces</h3>The device offers local control using its on-board button. The button can be used to cycle between the available clock faces. The following clock faces are available: <ol><li>Small clock with temperature - the default one on startup </li><li>Small clock with seconds </li></ol> <figure><img src="https://projects.arduinocontent.cc/be68b97d-d0ca-409d-9325-f45f67784717.jpg"/><figcaption></figcaption></figure> <ol><li>Plasma clock with temperature </li></ol> <figure><img src="https://projects.arduinocontent.cc/5d2d9088-c536-428d-b84a-47e174669c1e.gif"/><figcaption></figcaption></figure> <ol><li>Big clock </li></ol> <figure><img src="https://projects.arduinocontent.cc/c3bd402c-61da-40ed-bcf3-1b3e88f1ed62.jpg"/><figcaption></figcaption></figure> <ol><li>Scrolling status message - scrolls the uptime, current date, sensor measurements and Zigbee info through the screen </li></ol><h3>Summary</h3>Now that the project is finished, you're hopefully the proud owner of a Zigbee-powered smart clock. There are many possibilities to take this project further. You can customize the vendor/product name to make it your own. Since the Nano Matter supports Matter, it's also possible to port the whole clock to use Matter instead of Zigbee. Maybe add a new type of sensor? The possibilities are practically endless, go and have fun with it! <h3>Notes</h3>The project can also work without the Modulino sensors installed - or with just one of the two installed. During startup the firmware automatically detects if any of the modules are not present and disables the related functionality. This means you can also build the project without all the required sensors, while accepting some limited functionality. The project is originally built for the Arduino Nano Matter, however it can easily be ported over to other Silicon Labs based Zigbee boards like the Silicon Labs xG24 Explorer Kit, SparkFun Thing Plus Matter or Seeed Studio XIAO MG24.If you end up building this project, drop me some pictures! If you get stuck during a build, don't hesitate to reach out. Happy making! </body></html>

Zigbee Smart Clock

Build a Zigbee-powered smart clock with temperature and humidity sensing and automatic display brightness