C-V2X RX Sample App

This Document walks through the cv2x_rx_app sample application.

1. Create Callback functions for ICv2xRadio and ICv2xRadioManager methods

// Globals
static Cv2xStatus gCv2xStatus;
static promise<ErrorCode> gCallbackPromise;
static shared_ptr<ICv2xRxSubscription> gRxSub;
static uint32_t gPacketsReceived = 0u;
static array<char, G_BUF_LEN> gBuf;

// Resets the global callback promise
static inline void resetCallbackPromise(void) {
    gCallbackPromise = promise<ErrorCode>();
}

// Callback function for Cv2xRadioManager->requestCv2xStatus()
static void cv2xStatusCallback(Cv2xStatus status, ErrorCode error) {
    if (ErrorCode::SUCCESS == error) {
        gCv2xStatus = status;
    }
    gCallbackPromise.set_value(error);
}

// Callback function for Cv2xRadio->createRxSubscription() and Cv2xRadio->closeRxSubscription()
static void rxSubCallback(shared_ptr<ICv2xRxSubscription> rxSub, ErrorCode error) {
    if (ErrorCode::SUCCESS == error) {
        gRxSub = rxSub;
    }
    gCallbackPromise.set_value(error);
}

Note: We can also use Lambda functions instead of defining global scope callback functions.

2. Get a handle to the ICv2xRadioManager object

int main {
    // Get handle to Cv2xRadioManager
    auto & cv2xFactory = Cv2xFactory::getInstance();
    auto cv2xRadioManager = cv2xFactory.getCv2xRadioManager();

3. Request the C-V2X status

We want to verify that the C-V2X RX status is ACTIVE before we try to receive data.

// Get C-V2X status and make sure Rx is enabled
assert(Status::SUCCESS == cv2xRadioManager->requestCv2xStatus(cv2xStatusCallback));
assert(ErrorCode::SUCCESS == gCallbackPromise.get_future().get());

if (Cv2xStatusType::ACTIVE == gCv2xStatus.rxStatus) {
    cout << "C-V2X RX status is active" << endl;
}
else {
    cerr << "C-V2X RX is inactive" << endl;
    return EXIT_FAILURE;
}

4. Get handle to C-V2X Radio

auto cv2xRadio = cv2xRadioManager->getCv2xRadio(TrafficCategory::SAFETY_TYPE);

5. Wait for C-V2X Radio to be ready

if (not cv2xRadio->isReady()) {
    if (Status::SUCCESS == cv2xRadio->onReady().get()) {
        cout << "C-V2X Radio is ready" << endl;
    }
    else {
        cerr << "C-V2X Radio initialization failed." << endl;
        return EXIT_FAILURE;
    }
}

6. Create RX Subscription and receive data using RX socket

resetCallbackPromise();
assert(Status::SUCCESS == cv2xRadio->createRxSubscription(TrafficIpType::TRAFFIC_NON_IP,
                                                          RX_PORT_NUM,
                                                          rxSubCallback));
assert(ErrorCode::SUCCESS == gCallbackPromise.get_future().get());

// Read from the RX socket in a loop
for (uint32_t i = 0; i < NUM_TEST_ITERATIONS; ++i) {
    // Receive from RX socket
    sampleRx();
}

7. Close RX Subcription

We supply the callback in this sample and check its status, but note that it is optional.

    resetCallbackPromise();
    assert(Status::SUCCESS == cv2xRadio->closeRxSubscription(gRxSub,
                                                             rxSubCallback));
    assert(ErrorCode::SUCCESS == gCallbackPromise.get_future().get());

    return EXIT_SUCCESS;
} // main