Input pin in pull up mode is being in high impedance state

[Vladyslav8989]

I have set PA3 pin as input with pull up mode. But testing this pin by multimeter I get high impendance state (0.5V) on it. Must be 3.3V (logical 1). I use stm32F417ZGT6. 

[Andrew Neil]

welcome to the forum.

Please see  How to write your question to maximize your chances to find a solution for best results.

In particular, Please give details of your hardware.

[Vladyslav8989]

Schematic of PA3 port connecting

[TDK]

The attached code initialized PA3 as input with pullup. No problems there. Nothing special about PA3.

The issue is likely with your hardware. It's also possible you're not measuring the actual pin. Show a picture of your setup, schematic, and what you're actually measuring.

[Vladyslav8989]

Schematic of PA3 port connecting

[waclawek.jan]

Note, that the internal pullup is nominally 40kOhm, so it won't provide enough current to overcome an external 10kOhm pulldown to a valid logic 1 state.

Actually, if VDD is around 3V, a 40kOhm/10kOhm divider you have should result in cca 0.6V, matching your observation.

JW

[Vladyslav8989]

What I should to do to have logical 1 on PA3 input with pull up mode?

[mfgkw]

> What I should to do to have logical 1 on PA3 input with pull up mode?

Remove your external resistors...

[Vladyslav8989]

I see... maybe... My mentor something about this possible necessity was mentioned too. But for this need to dismount resistor from pcb. For this need access to soldering iron. So, it's complicated. Maybe some other ways?

[Andrew Neil]

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@Vladyslav8989 wrote:

My mentor something about this possible necessity was mentioned too.

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Time to go back to this Mentor again, then - and clarify that.

Maybe show them this thread?

 

BTW: Note that everyone can see every post - there's no need to repeat posts with the same information for different people.

You can mention multiple people in one post with '@'

[waclawek.jan]

No.