Uart sending process was interrupted

[copperface]

void uart_init(void){
uint32_t err_code;

const app_uart_comm_params_t comm_params =
  {
    .rx_pin_no    = RX_PIN_NUMBER,
    .tx_pin_no    = TX_PIN_NUMBER,
    .rts_pin_no   = RTS_PIN_NUMBER,
    .cts_pin_no   = CTS_PIN_NUMBER,
    .flow_control = APP_UART_FLOW_CONTROL_DISABLED,
    .use_parity   = false,
    .baud_rate    = UART_BAUDRATE_BAUDRATE_Baud9600
  };

APP_UART_FIFO_INIT(&comm_params,
                    UART_BUF_SIZE,
                    UART_BUF_SIZE,
                    uart_event_handler,
                    APP_IRQ_PRIORITY_LOW,
                    err_code);


APP_ERROR_CHECK(err_code);}

This is my uart initial function. When I send some data via uart, the process was interrupted by other process, I don't know which one could cause this issue?( I have 3 timers, 100ms, 1.5s and 60s, and BLE service)

After I set the priority level to APP_IRQ_PRIORITY_HIGH, the code works ok.

So which one could cause this problem?

[FormerMember]

When using the softdevice, the radio handling has the priority APP_IRQ_PRIORITY_HIGHEST, but the application level events have priority APP_IRQ_PRIORITY_MID. It means that if the UART has priority APP_IRQ_PRIORITY_LOW and if there are some BLE application events, the UART will be interrupted.

The only problem I can think of, if having UART priority higher than BLE application events, is if there is a BLE application event that require the application to send a reply (for example during a bonding process) and it is not able to interrupt a UART interrupt.

[copperface]

Thank you for your answer. So is there a better way to avoid interrupt sending data via UART?

[FormerMember]

My previous answer was not entirely correct. When using BLE and UART, the radio will have higher priority than UART. It means that UART will have to be delayed when the radio radio is being used. So it is therefore not possible to avoid the UART pauses when used in conjuction with UART. To be sure to not loose any data on the UART, I would recommend you to use flow control (HWFC).