How do I get the uart interrupt going?

[Mitch996]

I''m trying to run a piece of PERIPHERAL example code running on a nrf51422 devboard

I'm using sdk 8.0 and the example's relative path is:

>nRF51_SDK_8.1.0_b6ed55f\examples\peripheral\uart

Now, this is what I'm hoping for. In most other examples, there's gonna be this initialization function where an interrupt handler will be present. I do modification to that handler, press ctrl-c, press ctrl-v and viola! My project moves forward by 80%.

This specific example however, deoesn't seem to operate by that principle. I found the interrupt handler, this to be more precise:

void UART0_IRQHandler(void)
{
    // Handle reception
    if (NRF_UART0->EVENTS_RXDRDY != 0)
    {
        uint32_t err_code;

        // Clear UART RX event flag
        NRF_UART0->EVENTS_RXDRDY = 0;

        // Write received byte to FIFO
        err_code = app_fifo_put(&m_rx_fifo, (uint8_t)NRF_UART0->RXD);
        if (err_code != NRF_SUCCESS)
        {
            app_uart_evt_t app_uart_event;
            app_uart_event.evt_type          = APP_UART_FIFO_ERROR;
            app_uart_event.data.error_code   = err_code;
            m_event_handler(&app_uart_event);
        }
        // Notify that new data is available if this was first byte put in the buffer.
        else if (FIFO_LENGTH(m_rx_fifo) == 1)
        {
            app_uart_evt_t app_uart_event;
            app_uart_event.evt_type = APP_UART_DATA_READY;
            m_event_handler(&app_uart_event);
        }
        else
        {
            // Do nothing, only send event if first byte was added or overflow in FIFO occurred.
        }
    }

    // Handle transmission.
    if (NRF_UART0->EVENTS_TXDRDY != 0)
    {
        // Clear UART TX event flag.
        NRF_UART0->EVENTS_TXDRDY = 0;
        on_uart_event(ON_TX_READY);
    }

    // Handle errors.
    if (NRF_UART0->EVENTS_ERROR != 0)
    {
        uint32_t       error_source;
        app_uart_evt_t app_uart_event;

        // Clear UART ERROR event flag.
        NRF_UART0->EVENTS_ERROR = 0;

        // Clear error source.
        error_source        = NRF_UART0->ERRORSRC;
        NRF_UART0->ERRORSRC = error_source;

        app_uart_event.evt_type                 = APP_UART_COMMUNICATION_ERROR;
        app_uart_event.data.error_communication = error_source;

        m_event_handler(&app_uart_event);
    }
}

I placed a break point at

        if (NRF_UART0->EVENTS_RXDRDY != 0)

and then I set the breakpoint hitcount to 6.

After the break point were hit 6 times I took a look at the RXD register in my keil watch 2 window, nothing, all 0s. The TXD has a value but that doesn't really mean anything.

What I' want is that I want a interrupt handler that I can migrate with ease, or at least I can view the content of what has been received on my devboard.

So... what did I do wrong?  Why is the RXD register always zeros? Anything I forgot to enable?

[Jørgen Holmefjord]

What are you expecting to see in the RXD register? Did you start any receive operations? If you place the breakpoint at the if-check, this will be hit by any following events in the handler, not just the RX event. Have you tried placing the breakpoint inside the EVENTS_RXDRDY if-check? If your breakpoint is hit, the IRQ handler seems to be working as expected.