Using multiple UART instances on the nrf52840

[Tim Adu]

Hello,

Here's my current setup:

I am using the nrf52840 SoC for development, which as I understand, has 2 UART instances available. One instance is being used for a third party chip. This means I am no longer able to use UART for logging (I had to disable the UART backend and enable the RTT backend instead).

Now I would very much like to use the UART backend for logging, as I am particularly interested in using the CLI commands feature for doing some automated testing.

So, how do I make use of the other UART instance, and possibly bind it to the logger UART backend?

Thanks

[RK]

You are using the nRF52840 chip or you are using Nordic's development board based off the chip? Two rather different things. If you are using the chip in a custom design you can do whatever you want, if you are using the nRF52840 dev kit then yes one of the two UARTs is presented via a USB-CDC device as a serial port. You can just open that serial device on your PC/linux box/mac and read it as a .. serial device and you can log via the UART backend. That's the point of the logging interface, you can select whether it's presented via RTT or through the UART. And if you want to connect directly to the UART with a UART you can cut the solder bridges (see the manual). 

I think you're overcomplicating it - yes one UART goes via a third party chip, however it does that in order that you can open it as a serial device on your computer, it's not stolen from you, it's made available to you in a consumable form. I think that's what you actually want. 

[awneil]

I think you've missed the point - I think he's asking how he can use the two UARTs on the nRF52840 at the same time...?

[Tim Adu]

Precisely!
And I'm currently using the nrf52840 development kit, but will eventually move to a custom board

[awneil]

I don't know - I'm following this thread to find out!

I guess the easiest approach would probably to use the default UART for the NRF_LOG, and then select the other one for your "custom chip" comms ... ?

[Tim Adu]

That makes perfect sense;  but it's not exactly obvious how to select the other UART instance.
Thanks anyways for backing me up (that's why I responded to your thread).

[awneil]

Presumably, in what you currently have for your "custom chip" comms, there must be a "UART init" somewhere early on ... ?