Repurposing Thingy:91X Qwiic Connector Pins (P0.03/P0.04) for UART Communication - Official Support Confirmation

[Nekhil R]

Hi Nordic team,

I’m working on a custom LoRa interface using the Thingy:91X, and I’d like to know whether the Qwiic connector pins (P0.03 – SDA, and P0.04 – SCL) can be repurposed for UART communication.

According to the documentation, these pins are connected to the I²C bus by default and routed through level shifters. However, it’s also mentioned that they can be used as GPIOs by cutting SB8 and SB9.

My specific questions are:
1. After cutting SB8 and SB9, is it safe and officially supported to use P0.03 and P0.04 as UART TX/RX?
2. Will the existing level shifter (U24) on those lines interfere with UART signals, or can they be used without hardware modification beyond cutting the solder bridges?
3. Will standard UART baud rates (e.g., 9600 to 115200) work reliably over those pins?

My goal is to connect a LoRa-E5 module via UART using the existing Qwiic connector, to avoid soldering directly to test points.

Any guidance or confirmation would be greatly appreciated!

Thanks,
Nekhil

[Menon]

Hello,

I believe that cutting SB8 and SB9 physically removes the level shifter from the signal path, so it won’t interfere, and P0.03 and P0.04 can then be used as UART RX/TX. However, I do have some confusion regarding this, so I’m checking internally to get more clarity. I’ll update you as soon as I have more information.

Kind regards,
Abhijith