nRF52 UART Lock Up in NCS Connect

[NautDesigner]

We are seeing an issue where we are connecting to an LTE/GPS chip via interrupt UART. Things work great until have an irregular amount of time, communication to the LTE chip is no longer possible. If we remove power from the LTE chip and then power it back up, we still are unable to communicate. The only thing that resolves the issue is to restart the nRF52.

Any thoughts on what we can do to reset the UART?

[NautDesigner]

From what I can see, it is RX that is the problem, not TX. 

[Einarh]

Hello!

Things work great until have an irregular amount of time

Can you please expand on what you mean by this?

NautDesigner said:

From what I can see, it is RX that is the problem, not TX

Can you also explain how you came to this conclusion?

Best regards,

Einar

[Einarh]

NautDesigner said:

Nothing to log. Just send data and nothing returns.

What do you mean? If something goes wrong there is likely something getting logged:

http://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/services/logging/index.html

[NautDesigner]

Currently set to LOG_LEVEL_DBG which isn't outputting anything. What level would we need to get more indepth info? We also wouldn't want to show this level of detail until the issue occurs. Is there a way to restart/re-init the UART on the nRF52?

[Einarh]

I see, then logging is already enabled, strange that you're not getting any warnings.

Have you done any debugging to figure out exactly where in your code something goes wrong?

Also, it looks like you're using the Zephyr UART API, have you considered using the nrfx UARTE driver?

[NautDesigner]

Using NCS. Is there a way to restart/re-init the UART? Right now when this happens, rebooting the nRF52 is the only option that fixes it.

[Einarh]

Have you tried uart_irq_rx_disable/uart_irq_rx_enable?

You could also look into the Power Management module.

Though I still believe the best way to handle this would be to figure out what is actually going wrong so you can avoid ending up in this crashed state at all.