I2C SDA pin broken?

[TNils.1]

Hi

I am trying to configure I2C2 on an STM32F405RG on pins PB10/SCL and PB11/SDA, but I am getting very strange output on SDA.

STM32 is I2C master. Using I2C example from STM32F4-Discovery folder.

Using 4k7 ohm pull-ups to 3.3V.

Is the output pin broken, or what could I have missed?

Top is SCL and Bottom is SDA, trying to initiate communication repeatedly,

I would have tried I2C1 instead but the MCU is on a custom PCB and those pins are already occupied.

[TNils.1]

Ok, so I patched the board and tried I2C1 on PB8 and 9 instead.

Exact same behaviour. So clearly something is wrong.

I am trying to run the STM32Cube_FW_F4_V1.25.0\Projects\STM32F4-Discovery\Examples\I2C\I2C_TwoBoards_ComPolling example downloaded the other day.

Any ideas?

Thanks!

[waclawek.jan]

Bad solder joint? Broken wire? Try measuring directly at the pin, try to wiggle the pin as GPIO output, try measuring the same signal with both probes.

JW

[TNils.1 · Accepted solution]

Thanks! Some times you just don't think about the obvious. Probe adjustment issue . Of course 🙂