I have a custom board with nrf52840 chipset that controls a GSM modem over UART, and this setup works just fine (zephyr project).
Now, I'm trying to replicate this setup with an nrf52840DK board controlling dev kit of the same modem, but I don't see any activity on the UART Tx line.
I'm using the exact same project that works fine on the custom board. Are there any specific configurations that need to be set when using the DK?
Hi again Vidar,
Tx line is working fine, I was using wrong settings on the oscilloscope!
Thanks a lot for your support.
Have you checked if the UART pins you use are available on the DK board and that they aren't routed to any buttons or LEDs (see silkscreen on the backside)? P0.26 and P0.27 are normally available.
I just tried P0.27 for Tx and still nothing happens on it. "I'm using an oscilloscope to probe the line"
Can you double-check that PSEL.TXD is set correctly? Also, does the application appear to function normally except for the missing UART transmissions?
I'm new to the zephyr development environment, so I don't know what the best way to check the registers would be? I will look into that.
The application looks to be working fine, since I can probe the correct activity on the pin used for the modem power up control.
Is probably fastest to just read it with nrfjprog from the command line if you are familiar with this tool.
Example: reading PSEL.TXD for UARTE0
$ nrfjprog --memrd 0x4000250C
You can also read the peripheral registers when debugging in VS code or Segger embedded Studio. Which IDE are you using?