Matter: Smoke CO Alarm

This sample demonstrates the usage of the Matter application layer to build a device capable of sensing smoke and carbon monoxide, and issuing an alarm if the their concentration is too high.

This device works as a Matter accessory device, meaning it can be paired and controlled remotely over a Matter network built on top of a low-power 802.15.4 Thread network and works as a Minimal Thread Device (MTD) in a Sleepy End Device (SED) variant. Additionally, it works as Matter Intermittently Connected Device (ICD) with a Short Idle Time (SIT) and Long Idle Time (LIT)

You can use this sample as a reference for creating your own application. See the Adding clusters to Matter application page for an overview of the process you need to follow.

Requirements 

The sample supports the following development kits:

Hardware platforms	PCA	Board name	Board target
nRF54LM20 DK	PCA10184	nrf54lm20dk	`nrf54lm20dk/nrf54lm20b/cpuapp` `nrf54lm20dk/nrf54lm20a/cpuapp`
nRF54L15 DK	PCA10156	nrf54l15dk	`nrf54l15dk/nrf54l15/cpuapp`
nRF54L15 DK (emulating nRF54L10)	PCA10156	nrf54l15dk	`nrf54l15dk/nrf54l10/cpuapp`
nRF5340 DK	PCA10095	nrf5340dk	`nrf5340dk/nrf5340/cpuapp`
nRF52840 DK	PCA10056	nrf52840dk	`nrf52840dk/nrf52840`

If you want to commission the Smoke CO Alarm device and control it remotely through a Thread network, you need to set-up the Thread Border Router and control it with the chip-tool, or use a commercial ecosystem controller. When this happens, you will also be able to control it through a Matter controller device configured on PC or smartphone. This requires additional hardware depending on the setup you choose.

Note

Matter requires the GN tool. If you are updating from the nRF Connect SDK version earlier than v1.5.0, see the GN installation instructions.

IPv6 network support 

The following development kits for this sample offer IPv6 network support for Matter over Thread:

nrf52840dk/nrf52840, nrf5340dk/nrf5340/cpuapp, nrf54l15dk/nrf54l15/cpuapp, nrf54lm20dk/nrf54lm20b/cpuapp, and nrf54lm20dk/nrf54lm20a/cpuapp board targets.

Overview 

The sample does not use real hardware smoke or CO sensors due to hardware limitations. Instead, it uses test event triggers to test issuing the device alarms, and LEDs to show the current device state. The smoke CO alarm detects the alarm conditions and issues the appropriate alarm using different LED patterns.

Note

According to the Matter specification requirements, the smoke CO alarm device shall express alarms using both audible and visual indications. This sample does not use audible indications because of the lack of suitable hardware on supported development kits.

In case multiple alarm conditions are met, the device expresses only the alarm with the highest priority. After the alarm with the highest priority is stopped, the device starts expressing the next alarm in the priority order until all alarm conditions have ceased. The implementation demonstrated in this sample supports issuing the following alarms, listed from the highest priority to the lowest:

The sample implements two instances of a Power Source cluster:

Wired power source on the endpoint 0
Battery power source on the endpoint 1

The usage of power sources is implemented with a preference to select wired power source and switch to battery power source, only if the wired one is not available. The power source changes are emulated using test event triggers. Every power source can be independently enabled or disabled using a dedicated test event trigger.

You can test the device remotely over a Thread network, which requires more devices.

The remote control testing requires a Matter controller that you can configure either on a PC or a mobile device.

Smoke CO Alarm features 

The smoke CO alarm sample implements the following features:

Smoke alarm - Issued if allowed smoke concentration level is exceeded.
CO alarm - Issued if allowed carbon monoxide concentration level is exceeded.
Hardware fault alert - Issued if the device hardware is not operating properly.
Device self-test alert - Issued if the device self-test was started by the user.
End of service alert - Issued if the device service was ended either by the expiration date or other physical conditions, and it needs to be replaced.
Battery level alert - Issued if the device battery level is too low.
ICD LIT - The smoke CO alarm can be used as an Intermittently Connected Device (ICD) with a Long Idle Time (LIT).

Use the click to show toggle to expand the content.

ICD LIT device type

The device works as a Matter Intermittently Connected Device (ICD) with a Long Idle Time (LIT). The device starts operation in the Short Idle Time (SIT) mode and remains in it until it is commissioned to the Matter fabric and registers the first ICD client. It then switches the operation mode to LIT to reduce the power consumption.

In the LIT mode, the device is less responsive than in the SIT mode. However, you can request the device to become responsive, for example, to change its configuration. Press the Third Button to use the User Active Mode Trigger (UAT) feature.

See the User interface section for information on how to switch the operation modes.

Configuration 

This section describes the configuration options for the sample.

See Configuring and building for information about how to permanently or temporarily change the configuration.

The sample uses a prj.conf configuration file located in the sample root directory for the default configuration. It also provides additional files for different custom configurations. When you build the sample, you can select one of these configurations using the FILE_SUFFIX variable.

See Custom configurations and Providing CMake options for more information.

Note

If you are working with multiple devices, set a unique discriminator for each one, or commission them one at a time. See Matter device identification for more information.

The sample supports the following build configurations:

Smoke CO Alarm build configurations
Configuration	File name	FILE_SUFFIX	Supported board	Description
Debug (default)	`prj.conf`	No suffix	All from Requirements	Debug version of the application. Enables additional features for verifying the application behavior, such as logs.
Release	`prj_release.conf`	`release`	All from Requirements	Release version of the application. Enables only the necessary application functionalities to optimize its performance.
Internal memory only	—	`internal`	nRF54LM20 DK	Debug version of the application with external flash disabled. Enables the Smoke CO Alarm to work using internal memory only.

Advanced configuration options 

This section describes advanced configuration options that you can apply in this sample. Use the click to show toggle to expand the content.

Device firmware upgrade support

The sample supports device firmware upgrade (DFU) over-the-air (OTA) using the following protocols:

Matter OTA update protocol that uses the Matter operational network for querying and downloading a new firmware image.
Simple Management Protocol (SMP) over Bluetooth® LE. In this case, the DFU can be done either using a smartphone application or a PC command-line tool. This protocol is not part of the Matter specification.

In both cases, the MCUboot secure bootloader is used to apply the new firmware image.

The DFU over Matter is enabled by default. Additionally, you can enable the DFU over SMP by using the -DCONFIG_CHIP_DFU_OVER_BT_SMP=y build flag.

See Providing CMake options for instructions on how to add these options to your build.

The following platforms require external flash memory to perform the DFU:

nRF52840 DK
nRF5340 DK
nRF54L10 DK

You can run DFU without external flash memory on the nRF54L15 and nRF54LM20 DKs using the MCUboot image compression feature. To see if the sample supports this feature, check whether the internal build configuration is available in the build configuration table.

When building with nRF Connect for VS Code, add your desired dfu_build_flag to Extra CMake arguments. For example add -DCONFIG_CHIP_DFU_OVER_BT_SMP=y to enable DFU over BT SMP.

When building on the command line, run the following command with board_target replaced with the board target name of the hardware platform you are using (see Requirements), and dfu_build_flag replaced with the desired DFU build flag:

west build -b board_target -- dfu_build_flag

For example:

west build -b nrf54l15dk/nrf54l15/cpuapp -- -DCONFIG_CHIP_DFU_OVER_BT_SMP=y

Factory data support

In this sample, factory data support specific to the nRF Connect SDK is enabled by default for all configurations. This means that a new factory data set will be automatically generated when building for the target board.

To disable factory data support, set the following Kconfig options to n:

To learn more about factory data, read the Factory provisioning in Matter user guide.

Custom board with Nordic SoC

To prepare the sample to work with a custom board, complete the following steps:

Refer to the Create your board directory Zephyr guide and create your board directory.

Modify the contents of the board.yaml file according to the Write your board YAML user guide.

Update the Write your devicetree (all .dts and .dtsi files) to match your board’s requirements.

Write Kconfig files to enable all required Kconfig options for your board.

If you want to build your custom board with nRF70 Wi-Fi support, set the CONFIG_CHIP_WIFI and SB_CONFIG_WIFI_NRF70 Kconfig options to y.

If your device uses external flash, add its devicetree definition under the board/<board_name>_<soc_name>.overlay file, and set nordic,pm-ext-flash in the devicetree’s chosen configuration.

Refer to the Advanced Matter Kconfig options user guide, create your list of advanced configurations for your board, and apply the selected Kconfig options in the prj.conf file.

See the list of threads used in Matter application and adjust stack sizes according to your board and project requirements.

A custom board does not have support for LEDs and buttons by default. Therefore, you need to provide your own implementation of the nrf/samples/matter/common/src/board/board.cpp board file.

For more information, see the following guides:

Board Porting Guide and Custom Board, Devicetree and SOC Definitions to learn how to create a custom board directory.

Optimizing memory usage in Matter applications to learn how to optimize memory on your board.

Advanced Matter Kconfig options to learn about Matter configuration.

Matter hardware and memory requirements to learn about hardware requirements for Nordic Development Kits and to use as a reference when planning your custom board.

Internal memory only

For the nRF54LM20 DK, you can configure the sample to use only the internal RRAM for storage. It applies to the DFU as well, which means that both the currently running firmware and the new firmware to be updated will be stored within the device’s internal RRAM memory.

The DFU image fits in the internal flash memory if you use MCUboot image compression.

This configuration is disabled by default for the Matter Smoke CO Alarm sample. To enable it, set the FILE_SUFFIX CMake option to internal.

To build the sample for the nRF54LM20 DK with support for Matter OTA DFU and DFU over Bluetooth SMP, and using internal RRAM only:

Add -DCONFIG_CHIP_DFU_OVER_BT_SMP=y -DFILE_SUFFIX=internal to Extra CMake arguments in your build configuration.

west build -p -b nrf54lm20dk/nrf54lm20b/cpuapp -- -DCONFIG_CHIP_DFU_OVER_BT_SMP=y -DFILE_SUFFIX=internal

To build the sample for the same purpose in the release configuration:

Add -DCONFIG_CHIP_DFU_OVER_BT_SMP=y -DFILE_SUFFIX=internal -D<sample_name>_EXTRA_CONF_FILE=prj_release.conf to Extra CMake arguments in your build configuration, replacing <sample_name> with the actual sample name (for example light_bulb or matter_bridge).

Replace <sample_name> with the actual sample name and run:

west build -p -b nrf54lm20dk/nrf54lm20b/cpuapp -- -DCONFIG_CHIP_DFU_OVER_BT_SMP=y -DFILE_SUFFIX=internal -D<sample_name>_EXTRA_CONF_FILE=prj_release.conf

In this case, the size of the MCUboot secondary partition used for storing the new application image is approximately 30-40% smaller than it would be when using a configuration with external flash memory support.

User interface 

This section describes the user interface available on the development kit in this sample.

Buttons and LEDs map 

This section explains the names of Buttons and LEDs visible on a board depending on the development kits that are used in this sample user guide.

Buttons and LEDs map
DK family	First LED	Second LED	Third LED	Fourth LED	First Button	Second Button	Third Button	Fourth Button
nRF52 and nRF53 DKs	LED 1	LED 2	LED 3	LED 4	Button 1	Button 2	Button 3	Button 4
nRF54 DKs	LED 0	LED 1	LED 2	LED 3	Button 0	Button 1	Button 2	Button 3

Development kit interface 

This sample implements the following interface available on a development kit. While reading the names, refer to the Buttons and LEDs map.

First LED:

Shows the overall state of the device and its connectivity. The following states are possible:

Short Flash On (50 ms on/950 ms off) - The device is in the unprovisioned (unpaired) state and is waiting for a commissioning application to connect.
Rapid Even Flashing (100 ms on/100 ms off) - The device is in the unprovisioned state and a commissioning application is connected over Bluetooth LE.
Solid On - The device is fully provisioned.

Second LED:

Shows the state of the alarm. The following states are possible:

Even Flashing (300 ms on/300 ms off) - The smoke alarm is expressed.
Even Flashing (500 ms on/500 ms off) - The Identify command of the Identify cluster is received on the endpoint 1.
The command’s argument can be used to specify the duration of the effect.
Flashing in combination with Third LED and Fourth LED when other alarms are triggered.

Third LED:

Shows the state of the alarm. The following states are possible:

Even Flashing (300 ms on/300 ms off) - The CO alarm is expressed.
Flashing in combination with Second LED and Fourth LED when other alarms are triggered.

Fourth LED:

Shows the state of the alarm. The following states are possible:

Even Flashing (300 ms on/300 ms off) - The battery level low alarm is expressed.
Flashing in combination with Second LED and Third LED when other alarms are triggered.

Second, third and fourth LEDs combined:

Shows the state of the alarm. The following states are possible:

All three LEDs, Short Flash On (300 ms on/700 ms off) - The hardware fault alarm is expressed.
All three LEDs, Long Flash On (700 ms on/300 ms off) - The end of service alarm is expressed.
Flashing In Sequence from Second LED, through Third LED to Fourth LED (200 ms interval) - The self-test is triggered.

First Button:

Depending on how long you press the button:

If pressed for less than three seconds:
- If the device is not provisioned to the Matter network, it initiates the Simple Management Protocol (SMP) server and Bluetooth LE advertising for Matter commissioning. After that, the Device Firmware Update (DFU) over Bluetooth Low Energy can be started. Bluetooth LE advertising makes the device discoverable over Bluetooth LE for the predefined period of time (1 hour by default).
- If the device is already provisioned to the Matter network, it re-enables the SMP server. After that, the DFU over Bluetooth Low Energy can be started.
- If pressed for more than three seconds, it initiates the factory reset of the device. Releasing the button within three seconds of the initiation cancels the factory reset procedure.

Third Button:

Functions as the User Active Mode Trigger (UAT) button. For more information about Intermittently Connected Devices (ICD) and User Active Mode Trigger, see the Enable Matter Intermittently Connected Devices support documentation section.

SEGGER J-Link USB Port:: Used for getting logs from the device or for communicating with it through the command-line interface.

NFC port with antenna attached:: Optionally used for obtaining the onboarding information from the Matter accessory device to start the commissioning the device procedure while using a commercial ecosystem. See the Testing with commercial ecosystem section.

Building and running 

This section describes how to build the sample and commission it to the Matter network.

This sample can be found under samples/matter/smoke_co_alarm in the nRF Connect SDK folder structure.

To build the sample, follow the instructions in Building an application for your preferred building environment. See also Programming an application for programming steps and Testing and optimization for general information about testing and debugging in the nRF Connect SDK.

Note

When building repository applications in the SDK repositories, building with sysbuild is enabled by default. If you work with out-of-tree freestanding applications, you need to manually pass the --sysbuild parameter to every build command or configure west to always use it.

When building this sample with Sysbuild for an SoC that has a network core, the IPC radio firmware is automatically applied to the build. The IPC radio is one of the companion components in the nRF Connect SDK and allows to use the radio peripheral from another core in a multicore device. If needed, you can modify the IPC radio configuration in the prj.conf source file in the sample’s sysbuild/ipc_radio directory.

Before starting the commissioning procedure, make sure that the device is discoverable over Bluetooth LE. The device becomes discoverable automatically upon the device startup, but only for a predefined period of time (one hour by default). If the Bluetooth LE advertising times out, enable it again.

Testing 

This section shows how to test the sample. You can test it using your PC and the CHIP Tool for Linux or macOS or commercial ecosystem that supports Matter.

Testing with CHIP Tool 

Complete the following steps to test the Smoke CO Alarm device using CHIP Tool:

Prepare Matter network

To set up the Matter over Thread, complete the following steps:

Configure the Thread Border Router. See the Running OTBR using Docker section on the Thread Border Router page.
Download the prebuilt CHIP tool package from the Matter nRF Connect releases GitHub page. Make sure that the package is compatible with your nRF Connect SDK version.

Prepare your DK

To flash your DK with the sample and prepare it for testing, complete the following steps:

Connect the kit to the computer using a USB cable. The kit is assigned a serial port. Serial ports are referred to as COM ports on Windows, /dev/ttyACM devices on Linux, and /dev/tty devices on macOS. To list Nordic Semiconductor devices connected to your computer together with their serial ports, open a terminal and run the nrfutil device list command. Alternatively, check your operating system’s device manager or its equivalent.
Open a serial port connection to the kit using a terminal emulator that supports VT100/ANSI escape characters (for example, the Serial Terminal app). See Testing and optimization for the required settings and steps.
If the device was not erased during the programming, perform the factory reset procedure.

To restore the device settings and state to its factory set press the First Button for six seconds to initiate the factory reset of the device.

Commission to Matter network

To commission the device to the Matter network complete the following steps:

Obtain a Thread active dataset from OTBR:

Connect to the Raspberry Pi through USB or SSH.
Run the following commands:

sudo ot-ctl
> dataset active -x

Run the following command:

sudo docker exec -it otbr sh -c "ot-ctl dataset active -x"

The output should look like:

080000000000000000000300001735060004001fffe00208deadbeefcafe12340708fd123456789abc00000510112233445566778899aabbccddeeff00030a54657374576f726b3031010211220410aabbccddeeff00112233445566778899aa0c0402a0f7f8
Done

Run the following command and fill the <thread dataset> argument obtain in the previous step:
```
chip-tool pairing ble-thread 1 hex:<thread dataset> 20202021 3840
```

Observe the initial state

Observe that Second LED, Third LED and Fourth LED are turned off, which means that the device does not express any alarm.

Trigger the device self-test

In the interactive mode, trigger the device self-test by running the following command:

chip-tool smokecoalarm self-test-request 1 1

The Second LED, Third LED and Fourth LED will sequentially flash for 5 seconds.

Trigger the Smoke alarm

Replace the <test_event_enable_key> argument in the presented command with the value selected by you (by default, the enable key value is 00112233445566778899AABBCCDDEEFF):

generaldiagnostics test-event-trigger hex:<test_event_enable_key> 0x005c00000000009c 1 0

The Second LED will start blinking evenly with 300 ms interval.

Trigger the CO alarm

Replace the <test_event_enable_key> argument in the presented command with the value selected by you (by default, the enable key value is 00112233445566778899AABBCCDDEEFF):

generaldiagnostics test-event-trigger hex:<test_event_enable_key> 0x005c00000000009d 1 0

Nothing will change, because the CO alarm has lower priority than smoke alarm, so it will not be expressed.

Stop the Smoke alarm

In the interactive mode, stop the Smoke alarm by running the following command, replacing the <test_event_enable_key> argument with the value selected by you (by default, the enable key value is 00112233445566778899AABBCCDDEEFF):

generaldiagnostics test-event-trigger hex:<test_event_enable_key> 0x005c0000000000a0 1 0

The Second LED will be turned off and the Third LED will start blinking evenly with 300 ms interval, to express the CO alarm, as the next one in the order.

Testing with commercial ecosystem 

Before starting testing, ensure that the ecosystem supports the device types enabled in this sample. See the ecosystem manual page for instructions on how to use it.

When you start the commissioning procedure, the ecosystem controller must get the onboarding information from the Matter accessory device. The onboarding information representation depends on your commissioner setup.

For this sample, you can use one of the following onboarding information formats to provide the commissioner with the data payload that includes the device discriminator and the setup PIN code:

Smoke CO Alarm sample onboarding information

QR Code

QR Code Payload

Manual pairing code

Scan the following QR code with the app for your ecosystem:

MT:Y.K9042C00KA0648G00

34970112332

When the factory data support is enabled, the onboarding information will be stored in the build directory in the following files:

The factory_data.png file includes the generated QR code.

The factory_data.txt file includes the QR code payload and the manual pairing code.

This data payload also includes test Device Attestation, with test Certification Declaration, Product ID, and Vendor ID. These are used for Device Attestation within commissioning, and you can generate your own test Certification Declaration when you work on Matter end product.

Dependencies 

This sample uses the Matter library that includes the nRF Connect SDK platform integration layer:

Matter

In addition, the sample uses the following nRF Connect SDK components:

The sample depends on the following Zephyr libraries: