nrf_serial_rx_drain not clearing overrun error (?)

[Pete W]

Hi,

I'm using nrf_serial to configure and then read data from a GPS engine, but I am getting unrecoverable OVERRUN errors on start-up if the GPS device is sending data when I try to configure the serial port. I was hoping that I could just call the nrf_serial_rx_drain(xxx) function in my serial_event_handler to reset the buffer read and write pointers, but this has no effect, and the OVERRUN error appears on every subsequent character. Th only way I can get round it is by staging the initalisation as follows:

1. Initialise the serial port for TX only by setting the RX pin to NRF_UART_PSEL_DISCONNECTED.

2. Send a command to the GPS to switch off all messages.

3. Re-initialise the serial port to enable RX

4. Send a command to the GPS to enable the required messages.

but this is clunky and I still have to insert a short delay between each step to prevent the overruns.

Am I using nrf_serial_rx_drain(xxx) incorrectly, or misunderstood its function ?

Thanks

[Krzysztof Chruscinski]

Hi,

couple of questions. Are you using UART or UARTE underneath? What device are you using and which SDK? Are you using flow control?

If you are not using flow control (and don't plan to use it) I would recommend to check nrf_libuarte_async library for UARTE. It is capable of reliably receiving data of any length. nrf_serial stops and starts reception between every byte so it is possible to hit framing error if interrupt is not handled on time.

[Pete W]

Hi, sorry for the slow response - I thought I had replied to you. I'm using the nRF52840 and SDK15.3, and UARTE, with no flow control. I did try the libuarte_async library, and although I got the example working I had trouble integrating the ble stack and rest of my application - I couldn't set up sdk_config.h to get everything to compile. I'm not having any other issues with the nrf_serial library so I'll stick with that for now but will give libuarte_async another look when I get a chance.

Regards

Pete

[ovrebekk]

If it works, don't fix it ;)

If you have any more questions just let me know, and I will follow up with Krzysztof if needed. 

Best regards
Torbjørn