ADC reading problem on PIC18F452

[Sunny]

Thanks again. I'll follow your advice and do some test with another AD pin to try out the code first. Will let you know how it goes.

Best Regards!

[jfarkas]

The maximum recommended impedance for analog sources is 2.5 kΩ.
From datasheet

[Guest]

Thanks for the comment, jfarkas.

PCM Programmer, I removed all the connections to the AN0 pin, just used a 100ohm pot to adjust the voltage. However it's still the same thing (except that now it's 1.3 times instead of 1.25 times) ! I really don't know what's wrong there.

Then I used another bare board to build up a circuit just contains the PIC and the pot, it works.

I'm not going to spend more time on this one for now. Luckily I don't need the whole 5V range, so I'll just scale it in the code to have a "proper" pressure value.

Thanks again for your help!

[Ttelmah]

I'd be looking very carefully at how stable, and well decoupled the supply rail is. All the calculations you have done, are based on the chip having _exactly_ 5v at the supply pin....

Best Wishes

[Sunny]