Connecting Serial Port without USB on nRF52840DK

RE: Connecting Serial Port without USB on nRF52840DK

Einar Thorsrud — Fri, 11 Mar 2022 14:20:47 GMT

You can use any GPIO as long as it is available, though it is a good idea to avoid GPIOs that are close to the radio to avoid causing noise for the radio (those ar marked with "low frequency I/O only" in the pin assignments table).

RE: Connecting Serial Port without USB on nRF52840DK

Mehmet C. — Fri, 11 Mar 2022 13:56:11 GMT

Thank you for the answer.

> The default GPIO pins used for UART on the DK are connected to the onboard debugger

I thought there would be a jumper connection to override this and connect the output to the GPIO header.

> you need to select other GPIO pins

This might work. I couldn't find any information on this but can I use any GPIO pins for this purpose? Or is there a specific pins I would need to use?

RE: Connecting Serial Port without USB on nRF52840DK

Einar Thorsrud — Fri, 11 Mar 2022 13:01:16 GMT

Hi,

The default GPIO pins used for UART on the DK are connected to the onboard debugger and not the GPIO header when the debugger is active (you can see this on the explanation printed on the back of the DK PCB). To use the UART with another device you need to select other GPIO pins and configure our firmware to use those instead.

Regarding FW, if you use the nRF5 SDK we can use the UART example as reference. That use the pins specified in the board file, so you would have to change those in components/boards/pca10056.h. If you are using the nRF Connect SDK you can specify other pins in an overlay file, as shown here.