How to retrieve the Matter QR code?

[SunHuang]

Due to production requirements, I need to obtain the device's QR code. However, I found that the QR code can only be retrieved using the code snippet below after calling Nrf::Matter::StartServer().
Since there are several production test items that need to be performed, I would like to retrieve the QR code immediately after the hardware initialization.
Is there any way to obtain the QR code right after the device boots up?
My SDK version is NCS 2.9.0.

CHIP_ERROR Sunion::AppTask::StartApp()
{
	ReturnErrorOnFailure(Init());

	AppEvent event = {};

    DoorLockServer::Instance().SetSoundVolume(kLockEndpointId, Para.BuzzerPercent);


    char buffer[128 + 1];
    chip::MutableCharSpan qrCode(buffer);
    chip::RendezvousInformationFlags rendezvousFlags = chip::RendezvousInformationFlag::kBLE;

    if (GetQRCode(qrCode, rendezvousFlags) == CHIP_NO_ERROR)
    {
        ChipLogProgress(AppServer, "SetupQRCode: [%s]", qrCode.data());
    }
    else
    {
        ChipLogError(AppServer, "Failed to get QR code");
    }

	while (true) {
		k_msgq_get(&sAppEventQueue, &event, K_FOREVER);
		DispatchEvent(event);
		Ex_StateMachine();
	}

	return CHIP_NO_ERROR;
}

[SunHuang]

Hi,

I understand the steps you mentioned, but in my case, it's for mass production purposes. I need to transmit the QR code using a specific communication format. This protocol is for internal use. I must send out the QR code immediately upon startup.

[JONATHAN LL]

Checked internally and for production we do recommend to use our Factory Data module. Here is an instruction for QR code generation: https://docs.nordicsemi.com/bundle/ncs-latest/page/matter/nrfconnect_factory_data_configuration.html#generating_onboarding_codes . but it can be used independently based on VID/PID/discriminator and passcode.

You may use the helper python script and integrate it in production line, where factory_data partition content can be generated uniquely for each device. For development, we also include the passcode in the firmware which allows to print the URL to QR code in the shell command.

[SunHuang]

Hi,

I understand what you mean, and we do generate the QR code in that way as well. However, what I'm referring to is the production testing phase. I would like to verify that the hardware functions correctly before transmitting data using our custom communication protocol. You only need to tell me how to read the QR code before calling Nrf::Matter::StartServer().

[JONATHAN LL]

From the developers here, this is the recommendation.

When the customer generates QR code externally, but at the same time would like the accessory to generate and transmit QR code using some propriatary protocol.

To make it possible, Matter Factory Data must contain passcode. Then for example in our samples we do use the PrintOnboardingCodes function to print the QR code on UART.

Here is the example: https://github.com/nrfconnect/sdk-nrf/blob/main/samples/matter/common/src/app/matter_init.cpp#L345C2-L345C22

However, to save it to the buffer, please take a look at the functions here, which should help: https://github.com/nrfconnect/sdk-connectedhomeip/blob/3ccd6078b9b33af0fa6ddb71e51bb9860f9198a0/src/setup_payload/OnboardingCodesUtil.cpp

Regards,
Jonathan

[SunHuang]

JONATHAN LL said:

However, to save it to the buffer

I don't understand what you mean. Can't I get the string directly?

[JONATHAN LL]

https://github.com/nrfconnect/sdk-connectedhomeip/blob/3ccd6078b9b33af0fa6ddb71e51bb9860f9198a0/src/setup_payload/OnboardingCodesUtil.cpp#L52 

void PrintOnboardingCodes(const chip::PayloadContents & payload)
{
    char payloadBuffer[chip::QRCodeBasicSetupPayloadGenerator::kMaxQRCodeBase38RepresentationLength + 1];
    chip::MutableCharSpan qrCode(payloadBuffer);

    if (GetQRCode(qrCode, payload) == CHIP_NO_ERROR)
    {
        PrintQrCodeURL(qrCode);
    }
    else
    {
        ChipLogError(AppServer, "Getting QR code failed!");
    }

    chip::MutableCharSpan manualPairingCode(payloadBuffer);
    if (GetManualPairingCode(manualPairingCode, payload) == CHIP_NO_ERROR)
    {
        ChipLogProgress(AppServer, "Manual pairing code: [%s]", manualPairingCode.data());
    }
    else
    {
        ChipLogError(AppServer, "Getting manual pairing code failed!");
    }
}

[SunHuang]

Hi,

As I mentioned earlier, I must call PrintOnboardingCodes after executing Nrf::Matter::StartServer(), otherwise the system crashes. That’s why I’ve been emphasizing whether it’s possible to directly obtain the QR code string,because I believe it’s stored somewhere (likely in the factory data). So, how can I retrieve the QR code from anywhere in the program?