UART0->ERROSRC value 0x09

[Siddhesh]

Hardware:Two nrf52840 DK 
Software: SDK15.2

We have 2 development boards acting as a master and slave communicating over UART. We are using the serial library for this application.
When we pressed the reset button on the slave end, we get a "NRF_SERIAL_EVENT_DRV_ERR" event on the master side.
Debugging shows the value of the ERRORSRC to be 0x09. No data can be received on the master end when this driver error occurs.

We tried connecting a serial cable to the master and used Realterm to emulate the slave behavior. This had no errors on reception.

This concludes that the driver error is caused only when the slave resets and the reset state of the board causes a break on the master side.

Is there any way to resume reception after driver error or what is the correct action to be taken for such an error ?

[awneil]

Siddhesh said:

When we pressed the reset button on the slave end, we get a "NRF_SERIAL_EVENT_DRV_ERR" event

It is very common - to the extent that applications should expect it - to get a "junk" character or two at startup. Often with framing and/or parity errors.

This is probably what you're seeing.

The Nordic examples do not handle this sensibly:

 https://devzone.nordicsemi.com/f/nordic-q-a/41480/multiperipheral-nus-crashes/161714#161714

[Kenneth]

Unfortunately the examples and libraries have been setup to stop receiving data on error, so you would need to reinit() for instance the serial driver on error. Alternatively in this case I suspect you will avoid the error by adding an pull-up resistor on the UART_RX input pins on both DK.

[awneil]

The examples don't just "stop receiving" - they do a Fatal Error & crash!

It's easy enough to just handle the case of a UART error appropriately; eg, ignore the byte.

I did post an example of doing that in one of the past threads on this - but can't now find it.

Kenneth said:

you will avoid the error by adding an pull-up resistor

Maybe - but that just masks the symptom.

Your code really needs to properly handle UART errors.