The Project CHIP K32W061 Lighting Example demonstrates how to remotely control a light bulb. The light bulb is simulated using one of the LEDs from the expansion board. It uses buttons to test turn on/turn off of the light bulb. You can use this example as a reference for creating your own application.
The example is based on Project CHIP and the NXP K32W SDK, and supports remote access and control of a light bulb over a low-power, 802.15.4 Thread network.
The example behaves as a Project CHIP accessory, that is a device that can be paired into an existing Project CHIP network and can be controlled by this network.
The K32W061 lighting example application provides a working demonstration of a light bulb device, built using the Project CHIP codebase and the NXP K32W061 SDK. The example supports remote access (e.g.: using CHIP Tool from a mobile phone) and control of a light bulb over a low-power, 802.15.4 Thread network. It is capable of being paired into an existing Project CHIP network along with other Project CHIP-enabled devices.
The example targets the NXP K32W061 DK6 development kit, but is readily adaptable to other K32W-based hardware.
The CHIP device that runs the lighting application is controlled by the CHIP controller device over the Thread protocol. By default, the CHIP device has Thread disabled, and it should be paired over Bluetooth LE with the CHIP controller and obtain configuration from it. The actions required before establishing full communication are described below.
The example also comes with a test mode, which allows to start Thread with the default settings by pressing a button. However, this mode does not guarantee that the device will be able to communicate with the CHIP controller and other devices.
Deployment of this firmware configuration requires the K32W061 board setups using the K32W061 module board, SE051 Expansion board and Generic Expansion board as shown below:
The SE051H Secure Element extension may be used for best in class security and offloading some of the Project CHIP cryptographic operations. Depending on your hardware configuration, choose one of the options below (building with or without Secure Element). NOTE: the SE051H is a derivative of the SE051 product family (see http://www.nxp.com/SE051) including dedicated CHIP support in addition to the SE051 feature set. See the material provided separately by NXP for more details on SE051H.
In this example, to commission the device onto a Project CHIP network, it must be discoverable over Bluetooth LE. For security reasons, you must start Bluetooth LE advertising manually after powering up the device by pressing Button USERINTERFACE.
In this example, the commissioning procedure (called rendezvous) is done over Bluetooth LE between a CHIP device and the CHIP controller, where the controller has the commissioner role.
To start the rendezvous, the controller must get the commissioning information from the CHIP device. The data payload is encoded within a QR code, printed to the UART console and shared using an NFC tag. For security reasons, you must start NFC tag emulation manually after powering up the device by pressing Button 4.
Last part of the rendezvous procedure, the provisioning operation involves sending the Thread network credentials from the CHIP controller to the CHIP device. As a result, device is able to join the Thread network and communicate with other Thread devices in the network.
The example application provides a simple UI that depicts the state of the device and offers basic user control. This UI is implemented via the general-purpose LEDs and buttons built in to the OM15082 Expansion board attached to the DK6 board.
LED D2 shows the overall state of the device and its connectivity. Four states are depicted:
LED D3 shows the state of the simulated light bulb. When the LED is lit the light bulb is on; when not lit, the light bulb is off.
Button SW2 can be used to reset the device to a default state. A short Press Button SW2 initiates a factory reset. After an initial period of 3 seconds, LED2 D2 and D3 will flash in unison to signal the pending reset. After 6 seconds will cause the device to reset its persistent configuration and initiate a reboot. The reset action can be cancelled by press SW2 button at any point before the 6 second limit.
Button SW3 can be used to change the state of the simulated light bulb. This can be used to mimic a user manually operating a switch. The button behaves as a toggle, swapping the state every time it is pressed.
Button SW4 can be used for joining a predefined Thread network advertised by a Border Router. Default parameters for a Thread network are hard-coded and are being used if this button is pressed.
The remaining two LEDs (D1/D4) and button (SW1) are unused.
Directly on the development board, Button USERINTERFACE can be used for enabling Bluetooth LE advertising for a predefined period of time. Also, pushing this button starts the NFC emulation by writing the onboarding information in the NTAG.
In case the OM15082 Expansion board is not attached to the DK6 board, the functionality of LED D2 and LED D3 is taken over by LED DS2, respectively LED DS3, which can be found on the DK6 board.
Also, by long pressing the USERINTERFACE button, the factory reset action will be initiated.
In order to build the Project CHIP example, we recommend using a Linux distribution (the demo-application was compiled on Ubuntu 20.04).
Download K32W0 SDK 2.6.6 for Project CHIP. Creating an nxp.com account is required before being able to download the SDK. Once the account is created, login and follow the steps for downloading SDK_2_6_6_K32W061DK6 (required for K32W061 flavor). The SDK Builder UI selection should be similar with the one from the image below. 
Start building the application either with Secure Element or without
user@ubuntu:~/Desktop/git/connectedhomeip$ export NXP_K32W0_SDK_ROOT=/home/user/Desktop/SDK_2_6_6_K32W061DK6/
user@ubuntu:~/Desktop/git/connectedhomeip$ source ./scripts/activate.sh
user@ubuntu:~/Desktop/git/connectedhomeip$ cd examples/lighting-app/nxp/k32w/k32w0
user@ubuntu:~/Desktop/git/connectedhomeip/examples/lighting-app/nxp/k32w/k32w0$ gn gen out/debug --args="k32w0_sdk_root=\"${NXP_K32W0_SDK_ROOT}\" chip_with_OM15082=1 chip_with_ot_cli=0 is_debug=false chip_crypto=\"tinycrypt\" chip_with_se05x=0 chip_pw_tokenizer_logging=true mbedtls_repo=\"//third_party/connectedhomeip/third_party/nxp/libs/mbedtls\""
user@ubuntu:~/Desktop/git/connectedhomeip/examples/lighting-app/nxp/k32w/k32w0$ ninja -C out/debug
user@ubuntu:~/Desktop/git/connectedhomeip/examples/lighting-app/nxp/k32w/k32w0$ $NXP_K32W0_SDK_ROOT/tools/imagetool/sign_images.sh out/debug/
- with Secure element
Exactly the same steps as above but set chip_with_se05x=1 in the gn command
and add argument chip_enable_ota_requestor=false
Note that option chip_enable_ota_requestor=false are required for building with Secure Element. These can be changed if building without Secure Element
- for K32W041AM flavor:
Exactly the same steps as above but set build_for_k32w041am=1 in the gn command.
Also, select the K32W041AM SDK from the SDK Builder.
Also, in case the OM15082 Expansion Board is not attached to the DK6 board, the build argument (chip_with_OM15082) inside the gn build instruction should be set to zero. The argument chip_with_OM15082 is set to zero by default.
In case that Openthread CLI is needed, chip_with_ot_cli build argument must be set to 1.
In case signing errors are encountered when running the “sign_images.sh” script install the recommanded packages (python version > 3, pip3, pycrypto, pycryptodome):
user@ubuntu:~$ python3 --version Python 3.8.2 user@ubuntu:~$ pip3 --version pip 20.0.2 from /usr/lib/python3/dist-packages/pip (python 3.8) user@ubuntu:~$ pip3 list | grep -i pycrypto pycrypto 2.6.1 pycryptodome 3.9.8
The resulting output file can be found in out/debug/chip-k32w0x-light-example.
Program the firmware using the official OpenThread Flash Instructions.
All you have to do is to replace the Openthread binaries from the above documentation with out/debug/chip-k32w0x-light-example.bin if DK6Programmer is used or with out/debug/chip-k32w0x-light-example if MCUXpresso is used.
The tokenizer is a pigweed module that allows hashing the strings. This greatly reduces the flash needed for logs. The module can be enabled by building with the gn argument chip_pw_tokenizer_logging=true. The detokenizer script is needed for parsing the hashed scripts.
The python3 script detokenizer.py is a script that decodes the tokenized logs either from a file or from a serial port. It is located in the following path examples/platform/nxp/k32w/k32w0/scripts/detokenizer.py.
The script can be used in the following ways:
usage: detokenizer.py serial [-h] -i INPUT -d DATABASE [-o OUTPUT] usage: detokenizer.py file [-h] -i INPUT -d DATABASE -o OUTPUT
The first parameter is either serial or file and it selects between decoding from a file or from a serial port.
The second parameter is -i INPUT and it must se set to the path of the file or the serial to decode from.
The third parameter is -d DATABASE and represents the path to the token database to be used for decoding. The default path is out/debug/chip-k32w0x-light-example-database.bin after a successful build.
The forth parameter is -o OUTPUT and it represents the path to the output file where the decoded logs will be stored. This parameter is required for file usage and optional for serial usage. If not provided when used with serial port, it will show the decoded log only at the stdout and not save it to file.
The token database is created automatically after building the binary if the argument chip_pw_tokenizer_logging=true was used.
The detokenizer script must be run inside the example's folder after a successful run of the scripts/activate.sh script. The pw_tokenizer module used by the script is loaded by the environment. An example of running the detokenizer script to see logs of a lighting app:
python3 ../../../../../examples/platform/nxp/k32w/k32w0/scripts/detokenizer.py serial -i /dev/ttyACM0 -d out/debug/chip-k32w0x-light-example-database.bin -o device.txt
The building process will not update the token database if it already exists. In case that new strings are added and the database already exists in the output folder, it must be deleted so that it will be recreated at the next build.
Not all tokens will be decoded. This is due to a gcc/pw_tokenizer issue. The pw_tokenizer creates special elf sections using attributes where the tokens and strings will be stored. This sections will be used by the database creation script. For template C++ functions, gcc ignores these attributes and places all the strings by default in the .rodata section. As a result the database creation script won't find them in the special-created sections.
If run, closed and rerun with the serial option on the same serial port, the detokenization script will get stuck and not show any logs. The solution is to unplug and plug the board and then rerun the script.
Note: This solution is temporary.
In order to use the tinycrypt ecc operations, use the following build arguments:
NXPmicro/mbedtls library (mbedtls_repo=\"//third_party/connectedhomeip/third_party/nxp/libs/mbedtls\").To disable tinycrypt ecc operations, simply build with chip_crypto="mbedtls" and with or without mbedtls_repo. If used with mbedtls_repo the mbedtls implementation from NXPmicro/mbedtls library will be used.
The internal flash needs to be prepared for the OTA process. First 16K of the internal flash needs to be populated with a Secondary Stage Bootloader (SSBL) related data while the last 8.5K of flash space is holding image directory related data (PSECT). The space between these two zones will be filled by the application.
The SSBL can ge generated from one of the SDK demo examples. The SDK demo example needs to be compiled inside MCUXpresso with the define PDM_EXT_FLASH. The SSBL demo application can be imported from the Quickstart panel: Import SDK example(s) -> select wireless->framework->ssbl application.
The SSBL project must be compiled using the PDM_EXT_FLASH define.
Once compiled, the required ssbl file is called k32w061dk6_ssbl.bin
Before writing the SSBL, it it recommanded to fully erase the internal flash:
DK6Programmer.exe -V 5 -P 1000000 -s <COM_PORT> -e Flash
k32w061dk6_ssbl.bin must be written at address 0 in the internal flash:
DK6Programmer.exe -V2 -s <COM_PORT> -P 1000000 -Y -p FLASH@0x00="k32w061dk6_ssbl.bin"
First, image directory 0 must be written:
DK6Programmer.exe -V5 -s <COM port> -P 1000000 -w image_dir_0=0000000010000000
Here is the interpretation of the fields:
00000000 -> start address 0x00000000 1000 -> size = 0x0010 pages of 512-bytes (= 8kB) 00 -> not bootable (only used by the SSBL to support SSBL update) 00 -> SSBL Image Type
Second, image directory 1 must be written:
DK6Programmer.exe -V5 -s <COM port> -P 1000000 -w image_dir_1=00400000CD040101
Here is the interpretation of the fields:
00400000 -> start address 0x00004000 CD04 -> 0x4CD pages of 512-bytes (= 614,5kB) 01 -> bootable flag 01 -> image type for the application
DK6Programmer can be used for flashing the application:
DK6Programmer.exe -V2 -s <COM_PORT> -P 1000000 -Y -p FLASH@0x4000="chip-k32w0x-light-example.bin"
If debugging is needed, MCUXpresso can be used then for flashing the application. Please make sure that the application is written at address 0x4000:
The OTA topology used for OTA testing is illustrated in the figure below. Topology is similar with the one used for Matter Test Events.
The concept for OTA is the next one:
Computer #1 can be any system running an Ubuntu distribution. We recommand using TE 7.5 instructions from here, where RPi 4 are proposed. Also, TE 7.5 instructions document point to the OS/Docker images that should be used on the RPis. For compatibility reasons, we recommand compiling chip-tool and OTA Provider applications with the same commit id that was used for compiling the Lighting Application. Also, please note that there is a single controller (chip-tool) running on Computer #1 which is used for commissioning both the device and the OTA Provider Application. If needed, these instructions could be used for connecting the RPis to WiFi.
Build the Linux OTA provider application:
doru@computer1:~/connectedhomeip$ : ./scripts/examples/gn_build_example.sh examples/ota-provider-app/linux out/ota-provider-app chip_config_network_layer_ble=false
Build OTA image and start the OTA Provider Application:
doru@computer1:~/connectedhomeip$ : ./src/app/ota_image_tool.py create -v 0xDEAD -p 0xBEEF -vn 1 -vs "1.0" -da sha256 chip-k32w0x-light-example.bin chip-k32w0x-light-example.ota doru@computer1:~/connectedhomeip$ : rm -rf /tmp/chip_* doru@computer1:~/connectedhomeip$ : ./out/ota-provider-app/chip-ota-provider-app -f chip-k32w0x-light-example.ota
Build Linux chip-tool:
doru@computer1:~/connectedhomeip$ : ./scripts/examples/gn_build_example.sh examples/chip-tool out/chip-tool-app
Provision the OTA provider application and assign node id 1. Also, grant ACL entries to allow OTA requestors:
doru@computer1:~/connectedhomeip$ : rm -rf /tmp/chip_*
doru@computer1:~/connectedhomeip$ : ./out/chip-tool-app/chip-tool pairing onnetwork 1 20202021
doru@computer1:~/connectedhomeip$ : ./out/chip-tool-app/chip-tool accesscontrol write acl '[{"fabricIndex": 1, "privilege": 5, "authMode": 2, "subjects": [112233], "targets": null}, {"fabricIndex": 1, "privilege": 3, "authMode": 2, "subjects": null, "targets": null}]' 1 0
Provision the device and assign node id 2:
doru@computer1:~/connectedhomeip$ : ./out/chip-tool-app/chip-tool pairing ble-thread 2 hex:<operationalDataset> 20202021 3840
Start the OTA process:
doru@computer1:~/connectedhomeip$ : ./out/chip-tool-app/chip-tool otasoftwareupdaterequestor announce-ota-provider 1 0 0 0 2 0
doru@computer1:~/connectedhomeip$ : sudo docker kill $container_id
doru@computer1:~/connectedhomeip$ sudo ip link set dev eth0 down doru@computer1:~/connectedhomeip$ sudo ifconfig eth0 -multicast
If OTBR Docker image is used, then the “-B” parameter should point to the interface used for the backbone.
If Wi-Fi is used on a RPI4, then a 5Ghz network should be selected. Otherwise, issues related to BLE-WiFi combo may appear.