TIDC-CC2650STK-SENSORTAG: UART_read() returns zero

Hi everyone

There is a problem with the function UART_read(). I get a message on UART. Maximum message length is wantedRxBytes = 5. The message does not have a specific length. I need to know the exact number of bytes received. UART_read() always returns zero, however, the message is accepted. The source code of the program is presented below:

static void readCallback(UART_Handle handle, void *rxBuf, size_t size)
 {
     Event_post(eventH, UART_RX_COMPLETE);
 }

void taskFxn(UArg arg0, UArg arg1)
{
    eventH = Event_create(NULL, NULL);

    UART_Handle handle;
    UART_Params params;

    UART_Params_init(&params);
    params.writeDataMode = UART_DATA_BINARY;
    params.readDataMode  = UART_DATA_BINARY;
    params.readMode      = UART_MODE_CALLBACK;
    params.readCallback  = &readCallback;
    params.baudRate      = 2400;

    handle = UART_open(Board_UART, &params);
    UART_control(handle, UARTCC26XX_CMD_RETURN_PARTIAL_ENABLE, NULL);
    
    wantedRxBytes = 5;
    uint8_t rxBuf [wantedRxBytes];
    Int RxBytes = UART_read(handle, rxBuf, wantedRxBytes);

    uint8_t tBuf [5] = {0x01, 0x02, 0x03, 0x04, 0x05};

    while(true)
    {
        uint16_t events = Event_pend(eventH, Event_Id_NONE, 0xFFFFFFFF, BIOS_WAIT_FOREVER);

        if (events & UART_RX_COMPLETE)
        {
            UART_write (handle, tBuf, RxBytes);
            Task_sleep(10000);
            Event_post(eventH, UART_TX_COMPLETE);
        }

        if (events & UART_TX_COMPLETE)
        {
            RxBytes = UART_read(handle, rxBuf, wantedRxBytes);
        }

    }
}


Thanks in advance.