UART 1 vs 2 use

Issue: Understand the role of the two UARTs - exposing the correct port to allow upgrade of the 4200 / RUI programming

Setup: Creating a PCB with the 4200 + Nano Every


I’ve got my RAK811 / Arduino working just fine and now I’m working on a RAK4200 implementation. I’m too impatient to wait for my RAK4XXX breakout boards to arrive to try things so …

I can see the recommendation that I use UART2 to talk to my MCU (Arduino Nano Every).

  1. To be completely sure, does this UART provide the AT interface like the RAK811 does?

UART1 is showing as reserved:

  1. Is this the serial interface to update the main firmware?

  2. Does this also provide an interface to update the boot loader should that be required?

  3. Docs refer to this as a debug port as well, is this debug output from RUI & anything we code using RUI that references this port?


Yes,this debug port can using RUI code.
Please refer the document:

Hi @nmcc,

In the RAK4200 AT Command Manual, there are some description about UART1 and UART2 for reference, and i think it is helpful for you:

Thank you both, always best to check before sending off gerbers for PCBs.

@Fomi, I can’t find that document in downloads or that entry on the Quickstart or Documentation pages. Is there somewhere else to get info?