nRF52 UART locks up after OVERFLOW error

[Gordon]

Hi!

I'm using an NRF52 with app_uart. As expected at 115200 baud rate, I occasionally get overflow errors which I can see in my event handler.

However, after these errors the UART no longer receives any characters and is broken until I reinitialise it.

In nRF51 it seems you could write UART_ERRORSRC_OVERRUN_Clear to the error flags to clear the error, but the enum doesn't exist on nRF52 and there seems to be no mention of it in the docs. Looking at nrf_drv_uart it seems like it may clear the error flags, but then also disable interrupts.

So, if you're using app_uart to receive in an IRQ, what are you supposed to do in order to keep receiving even after getting an overflow event (this is with SD 3.0.0).

I should probably swap to app_uart_fifo - however I may very occasionally get overflows there and I want to be sure that the UART will keep working even in that case before I move to using fifos.

Thanks!

[Matt]

Can you enable flow control here? Does the other end (eg. the PC end) support the flow control lines ?

[Gordon]

I'm afraid not. It's for the Espruino JS interpreter so it's pretty general purpose and I can't guarantee there will always be flow control available. I'm honestly not worried about the overflows, it's the recovery afterwards that's an issue for me.

[Matt]

You need to consult with the Nordic experts then. As for my own application (PC <-serial -> N52832 <-ble-> N52832) again I do not have the luxury of utilizing flow control (the usb to ttl console cable does not come with flow control lines!) so I just implement my own makeshift flow control in the application message layer.

[Hung Bui]

Hi Gordon,

I afraid you will have to clear the event and reinit the uart drv:

nrf_drv_uart_uninit(&_uart_instance);
uart_init();

[Gordon]

Ok, thanks! Will that code also clear the overflow event?