error codes for APP_UART_COMMUNICATION_ERROR

[ms360]

I'm seeing a few of these errors in my uart evt handler

I cannot seem to find where these are enumerated in app_uart_fifo.c or nnrf_drv_uart.h or nrfx_uarte.h.

Question 1 - Where can I find these?  

<error> app: APP_UART_COMMUNICATION_ERROR : 1 00
<error> app: APP_UART_COMMUNICATION_ERROR : 5 00
<error> app: APP_UART_COMMUNICATION_ERROR : 4 00

Here is the code generating that log - 

NRF_LOG_ERROR("APP_UART_COMMUNICATION_ERROR : %d %02x", p_event->data.error_code, NRF_UARTE0->ERRORSRC);

When this happens, I try to run

app_uart_flush();

app_uart_close();

APP_UART_FIFO_INIT();

Question 2 - Is there a better way to recover? 

Thanks!

[Vidar Berg]

Hello,

The error message is including the value from the UART ERRORSRC register. 1 = OVERRUN, 2 = PARITY, and so on. 

When this happens, I try to run

app_uart_flush();

app_uart_close();

APP_UART_FIFO_INIT();

What happens if you don't do this? The app uart library should "recover" (i.e. re-enable reception) by itself if you just ignore the APP_UART_COMMUNICATION_ERROR event. 

Best regards,

Vidar

[ms360]

Thanks Vidar. The double digit hex value is the ERRORSRC register in my log. 

The single digit that precedes it is p_event->data.error_code, which is showing 1,4,5 in this case. 


I am considering trying nrfx_uarte to see if this still happens 

[Vidar Berg]

ms360 said:

The double digit hex value is the ERRORSRC register in my log. 

Thanks for pointing that out. However, it doesn't make sense that the error is 0 as the APP_UART_COMMUNICATION_ERROR event is only triggered after a "NRF_UARTE_EVENT_ERROR" event. The nrf52840 uart has 2 uarte instances, could it be that the app uart library is using the other instance in your code?

ms360 said:

am considering trying nrfx_uarte to see if this still happens

I'm afraid this won't help if there really is a communication error detected by the UART hw. app uart library is also built on top of this driver already.

[ms360]

From sdk_config - 

#define APP_UART_DRIVER_INSTANCE 0

I'm afraid this won't help if there really is a communication error detected by the UART hw. app uart library is also built on top of this driver already.

Does app uart use DMA? 

Thanks Vidar

[Vidar Berg]

UARTE with easyDMA is used by default, but it only uses '1' byte RX buffers. Are you able to share a code snippet showing revelant parts of your app uart callback?

[ms360]

Yup!

Just to note - I am seeing some overruns. Data is definitely getting lost

<error> app: APP_UART_COMMUNICATION_ERROR : 1 01
<error> app: APP_UART_COMMUNICATION_ERROR : 1 00

static void uart_handler(app_uart_evt_t *p_event) {
    switch (p_event->evt_type) {
        case APP_UART_DATA_READY: {
            uint32_t ret;
            do {
                ret = app_uart_get(&(rx_buf[rx_tail]));
                if (NRF_SUCCESS == ret) {
                    rx_tail++;
                    rx_tail %= UART_RX_BUF_SIZE;
                } else {
                    // NRF_LOG_ERROR("ret: %02x", ret);
                }
            } while (ret == NRF_SUCCESS);
        
            app_sched_event_put(NULL, 0, process_data);    
            break;
        }
        case APP_UART_COMMUNICATION_ERROR:
            NRF_LOG_ERROR("APP_UART_COMMUNICATION_ERROR : %d %02x", p_event->data.error_code, NRF_UARTE0->ERRORSRC);
            app_uart_flush();
            Flush_Uart();
            uart_busy = 0;
            break;
        case APP_UART_FIFO_ERROR:
            NRF_LOG_ERROR("APP_UART_FIFO_ERROR");
            break;
        case APP_UART_TX_EMPTY:
            break;
        case APP_UART_DATA:
            NRF_LOG_ERROR("APP_UART_DATA");
            break;
        default:
            NRF_LOG_ERROR("default");
    } 
}

[Vidar Berg]

Thank you. I see the problem now. So ERRORSRC register is being cleared from the nrfx_uarte.c->uarte_irq_handler() handler before it calls your uart_handler():

So the UART and the app are basically not able to keep up with the reception speed. Is using HW flow control an option?