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GPIO Read interact with GND or VCC

ULOK
Associate II

‎2024-11-05 03:43 PM

Hi,

I use STM32F103C8T6 a GPIO input pin to read a high or low signal from another GPIO output pin, and connect a 3Mohm resistor between two pins, and I notice touching GND with hand will influence the signal status, than I measure the resistance between GND and GPIO pin, it is around 10Mohm. I want to isolate the signal from GND interference, how should I do? I have to keep 3 Mohm resistor. will it be better if connect a capacitor between input pin and GND? or connect a large resistor in between?

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Andrew Neil
Evangelist III

‎2024-11-05 04:51 PM

@ULOK wrote:

I have to keep 3 Mohm resistor. 

Why??

At that level of resistance, it is to be expected that touching with a hand will be significant!

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ULOK
Associate II
In response to Andrew Neil

‎2024-11-05 05:01 PM

Hi, it is intended for hand detection, but touching GND will also be detected which is surprise. 3Mohm vs. 10(or 6Mohm), I want to increase the resistance to GND so that GND will not influence signal that much.

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