I2C1 has decided to stop working?

NicRoberts · ‎2026-01-27

NUCLEO WB55

For an unknown reason I2C1 has just stopped working. The BLE & UART are working but the boards (I've tested on 2 identical boards) are no longer talking to the sensors via I2C.

When I scope them up the traces for SCL & SDA are both flat lines (yes I checked the scope is working properly).

Frustratingly, this all worked before xmas.

Anyone any clue what could cause this?

Andrew Neil · ‎2026-01-27

Some more details of your setup would help:

How to write your question to maximize your chances to find a solution

@NicRoberts wrote:
Frustratingly, this all worked before xmas.

So what have you changed between then & now ?

@NicRoberts wrote:
SCL & SDA are both flat lines

High or low?

Can you toggle them just as plain GPIOs

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.