Software Hysteresis For A/D

[wuchy143]

Hello,

I have a PIC12F615 which I'm using it's 10bit A/D to read a POT from 0-5V. I'm then taking that A/D reading dividing it down by 4 so that I can use it to plug into a timer which I'm using for PWM. This gives me 8 bits of resolution for my PWM signal.

Problems: My PWM signals jumps around a lot due to the instability of the A/D reading. At times if you tune the pot correctly I am able to get the PWM to go back and forth between 2 levels.

I understand that I need to implement some software hysteresis to properly address this issue and was wondering if anyone had some good approaches for my current system.

Thanks

 

[ronsimpson]

You can read the ADC in 8 bit mode.
Have you thought of averaging 4 readings? Or averaging and through out any reading very different than the average.

 

[Gobbledok]

Yep averaging a few readings will work well. Add 4 x 10-bit values together and then divide by 16 to give you your 8-bit averaged result.

Also, because a pot is a slow moving analog signal you could put a small value capacitor on the analog input pin.