Resetting input pin hysterisis

Hello Experts,

I'm trying to use a digital pin to read a voltage level, to see if it high or low. The pin has a hysterisis. Trigging a low and high occurs at different levels.

The voltage level is fluctuating so the input pin may be triggered low and then at the time of reading it is actually somewhere inbetween. But I will see the Low that was triggered before.

I'm hoping that enabling the pullp resistor (internally) would set a high. Then, when reading the pin, a low will really be a true representation of the current voltage on the pin.

My worry is that enabling the pullup would be a problem since I have a live cirquit connected. this means that with the pullup I will have two different positive voltages connected to the same pin. Can this be a problem?

Thanks /Jonas

That will not be problem. Do not exceed the max input voltage.

Many thanks for your kind help! /Jonas

Jonasforssell: Hello Experts,

I'm trying to use a digital pin to read a voltage level, to see if it high or low. The pin has a hysterisis. Trigging a low and high occurs at different levels.

The voltage level is fluctuating so the input pin may be triggered low and then at the time of reading it is actually somewhere inbetween. But I will see the Low that was triggered before.

I'm hoping that enabling the pullp resistor (internally) would set a high. Then, when reading the pin, a low will really be a true representation of the current voltage on the pin.

My worry is that enabling the pullup would be a problem since I have a live cirquit connected. this means that with the pullup I will have two different positive voltages connected to the same pin. Can this be a problem?

Thanks /Jonas

There is only one voltage at the pin, the pull-up and the output impedance of the external circuit act as a voltage divider. If both are always in the 0 to 5V range then the pin is guaranteed to be in that range too since it is always somewhere between the two voltages.