RA0 (as ANALOG) and RA3 (as VREF+) usage question on PIC18F

[ik1wvq]

Hi,

I need to use RA0 as analog input, and RA3 as VREF+, with RA1 and RA2 as normal DIGITAL inputs/outputs. (on PIC18F2620)

It is possible to make this?

I ask this because I suppose what RA3 must be defined as ANALOG for
using as VREF, and then RA1 and RA2 also bacame defined as analog ...
(AN0_TO_AN3_ANALOG)

It is correct???

Thanks in advance.

regards

Mauro

[Ttelmah]

RA3, has to be defined as Vref, not as an analog input.

What you need, is:

setup_adc_ports(AN0 | VSS_VREF);

This says "set AN0 as an analog input" (first part of what you want), and then says "set the voltage reference 'low', to use Vss, and the voltage reference 'high' to use it's Vref input (second part...)".

The Vref settings are separate from the analog input selection.

Look at the section in the processor include file, for "Constants used in setup_adc_ports", and read the comments on the lines, and partiularly the second block of stuff headed "The following may be OR'ed in with the above using |".

Best Wishes