Issue with PA2 and PA12 pin in L432KC Nucleo

[xpp07]

I'm using a reflective sensor to measure speed. In my PCB, I wrongly connected PA12 to the output of the sensor. I actually needed PA2 to use it as TIM2_CH3. So I jumped PA12 and PA2. This pin is pulled up to 3.3V with a 10K resistor. With no sensor connected, I clearly should read 3.3V at PA2 input, as it's pulled up. But I'm reading 1.4V. I have an external power supply for the controller. When I power up ST Link through the USB connector, then I read the 3.3V correctly. What's happening here?

[waclawek.jan]

Depending on how exactly you power the target mcu, the STLink mcu might be unpowered, and then you are parasitically powering it through that solder bridge. Disconnect it.

JW