cause UART to crash by transmit data continuously

[leif]

Our project use 51822 and another MCU stm32 to transmit heart rate data by uart. then 51822 SPP heart rate to smart phone APP. Now, We meet a issue that 51822 UART will crash if coninuously transmit data over several minutes (i.e over 5 minutes) between STM32 and 51822. STM32 UART can send data to 51822 but 51822 UART can't receive it and send ACK to STM32. Even through we re-initialization 51822 UART but it take no effect. if transmit data time less than 3 Minutes the UART seem ok. we call your callback to init UART as below:

 const app_uart_comm_params_t comm_params =
    {
        RX_PIN_NUMBER,
        TX_PIN_NUMBER,
        RTS_PIN_NUMBER,
        CTS_PIN_NUMBER,
        APP_UART_FLOW_CONTROL_DISABLED, //APP_UART_FLOW_CONTROL_ENABLED
        false,
        UART_BAUDRATE_BAUDRATE_Baud57600  
    };
APP_UART_FIFO_INIT( &comm_params,
                       256,     
                       256,     
                       uart_event_handle,
                       APP_IRQ_PRIORITY_LOW,
                       err_code);
 We try to  decrease to  baud rate 38400 from 57600 but it still not fixed it. Another, i find if increase connection interval by modfiy min and max interval range that can delay UART crash time as below:
#define MIN_CONN_INTERVAL               MSEC_TO_UNITS(8, UNIT_1_25_MS)
/*< Minimum acceptable connection interval (20 ms), Connection interval uses 1.25 ms units. */
#define MAX_CONN_INTERVAL               MSEC_TO_UNITS(10, UNIT_1_25_MS)

what cause 51822 UART crash?

[RK]

You're probably overrunning the UART since you don't have flow control on and are using a high bitrate, eventually the softdevice interrupts for long enough the buffer fills, an error is flagged and depending on what the code does when there's an error (look at the code and see) the UART may appear to stop working. Have you checked the ERRORSRC register in the UART when you have this issue to see if any bits are set?

I doubt the UART has 'crashed', I'm sure it's still working away, but it's in an error condition the code you're using to drive it is not recovering from.

If you completely re-initialize the UART it should start receiving again, so it rather depends what you mean by 'even though we re-initialize .. ' and what the code you're using does on init if there was an outstanding error.

High baudrates + no flow control + softdevice isn't a recipe for success. STM32 MCUs support flow control, why don't you use it and make all your problems go away.

[baptiste]

Hi Leif, I suppose to have the same problem with my uart on NRF51822 after a time (between 30 and 1H30), the nrf51 stop to receive frame on rx (without any error reported by the driver), the frame is sent every 5 minutes. The only way is to reset the chip by the STM32. I would like to know how you resolve your issue ?, because at current time, i've no idea what is the problem, thank you for your help.