Why does Nucleo's PA 3 terminal show 3.3 V with ADC

[Ken Inoue]

Posted on July 25, 2017 at 01:56

Thank you for your patronage. 

I'm Japanese student. Sorry for my poor English.

I'm using STM32F334Nucleo.

Nucleo's PA 3 terminal indicates about 3.3 V in ADC in a situation where nothing is connected.

On the other hand, the PA0 terminal shows about 0V in the AD conversion in a situation where nothing is connected.

Why do these two differ?

[Tesla DeLorean]

Posted on July 25, 2017 at 02:49

Probably because it is connect to the VCP USART from the ST-LINK. Review the schematic

[Ken Inoue]

Posted on July 25, 2017 at 06:45

Thank you for your early reply. I was able to solve this problem. I am very grateful to you.

[Zt Liu]

Posted on July 25, 2017 at 02:57

this is your target mcu

belowed is your st-link

you should probably removed SB13 and connect SB62

[Tesla DeLorean]

Posted on July 25, 2017 at 03:46

Or just use the pins designated for the Arduino analogue interface.