ADC external comp pins

[hax]

Hi all,

I want to use the comparator pins on a 40x2 chip for reading adc10 voltages using an external precision voltage source for best accuracy.

The manual says the adcconfig Vref+ pin is A.3 and the Vref- pin is A.2, but in the picaxe pinouts section here http://www.picaxe.com/What-is-PICAXE/PICAXE-Pinouts/

it says that those pins are Comp2+ and Comp1+ respectively. Shouldn't they be Comp1+ and Comp1-? Also, looking at the pinouts page, what are the other A.0 and A.1 reference pins? How are they used, and are they used by another command?

 

[hax]

oh I have just found the Compsetup command. Never knew it could do that. So it looks like the ADCCONFIG command uses both internal comparators.

 

[hippy]

The ADC and Comparators are separate pieces of on-chip hardware, and it is common for on-chip hardware to share I/O pins. Looking at the PICmicro datasheet shows -

Leg 4 is C2IN+ and Vref-
Leg 5 is C1IN+ and Vref+

So it appears the PICAXE documentation is correct -

Leg 4, A.4 is Comp2+ and Vref-
Leg 5, A.5 is Comp1+ and Vref+