APP stucks in simple_uart.c

Question

Hi Guys,

i've a problem with the simple_uart.c module. I print some intermediate values with app_trace_log -> simple_uart.c and sometimes, the application stucks at:

void simple_uart_put(uint8_t cr)
{
    NRF_UART0->TXD = (uint8_t)cr;
      
    while (NRF_UART0->EVENTS_TXDRDY != 1) //<<<< in this line
    {
        // Wait for TXD data to be sent.
    }

    NRF_UART0->EVENTS_TXDRDY = 0;
}

Does anybody know, how i can avoid this or continue without resetting the device?

Thanks in advance, cheers

Nikita · Accepted Answer

I'd recommend not to send the data through uart from interrupts. I'd go with using TX circular buffer in which I'd store the data to be sent by uart. And in the main loop I'd check for any data in TX buffer to be sent and send it if there is any.

UPD:

Something like this:

#define UART_TX_BUF_SIZE   256 // Buf size is power of 2 for MASK. If you need more than 256 bytes then change buffer size and idxIN and idxOUT types to uint16_t
#define UART_TX_BUF_MASK   (UART_TX_BUF_SIZE-1)

volatile bool uart_tx_is_busy = false;
volatile uint8_t idxIN = 0; // Buffer index input data
uint8_t idxOUT = 0; // Buffer index output data
volatile uint8_t uart_tx_buffer[UART_TX_BUF_SIZE];

void put_data_in_uarf_buf(uint8_t data)
{
    uint8_t nested;
    sd_nvic_critical_region_enter(&nested);
    if (uart_tx_is_busy == false && idxIN == idxOUT)
    {
        uart_tx_is_busy = true;
        NRF_UART0->TXD = data;
    }
    else
    {
        uart_tx_buffer[idxIN++] = data;
#if UART_TX_BUF_SIZE != 256
        idxIN &= BUF_MASK;
#endif
    }
    sd_nvic_critical_region_exit(nested);
}
uint8_t get_data_from_uarf_buf(void)
{
    uint8_t data;
    data = uart_tx_buffer[idxOUT++];
#if UART_TX_BUF_SIZE != 256
    idxOUT &= BUF_MASK;
#endif
    return data;
}
...
    simple_uart_config(RTS_PIN_NUMBER, TX_PIN_NUMBER, CTS_PIN_NUMBER, RX_PIN_NUMBER, HWFC);
    // Enable UART interrupt
    NRF_UART0->INTENCLR = 0xffffffffUL;
    NRF_UART0->INTENSET = (UART_INTENSET_TXDRDY_Set << UART_INTENSET_TXDRDY_Pos);
...
    // Enter main loop.
    for (;;)
    {
        if (NRF_UART0->EVENTS_TXDRDY == 1)
        {
            NRF_UART0->EVENTS_TXDRDY = 0;
            uart_tx_is_busy = false;
        }
        if (uart_tx_is_busy == false && idxIN != idxOUT)
        {
            uart_tx_is_busy = true;
            NRF_UART0->TXD = get_data_from_uarf_buf();
        }
        app_sched_execute();
        power_manage();
    }

APP stucks in simple_uart.c

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