**RESOLVED** ADC module, only getting a max count of 511

[rmteo]

First time using the ADC module with a PIC18F4620 to measure 0-5V. Works fine to 2.50V, beyond that, the result stays constant. I checked ADResult and it shows 511 counts from 2.50-5.00V. Any ideas what I'm doing wrong?

[CharlieM]

Are you sure you have your AD registers set correctly?

[rmteo]

I'm using the default from the sample ADIn.bas, what should they be?

Code: Select all

TRISA.0 = 1        // configure AN0 as an input 
ADCON1.7 = 1       // set analogue input on PORTA.0 

[Jon Chandler]

Try changing the conversion time....I was having this same problem too, reading exactly half scale as maximum.

From the documentation:

sub SetConvTime(pValue as byte)
• pValue - ADC conversion time. Valid arguments are FOSC_2, FOSC_4,
FOSC_8, FOSC_16, FOSC_32, FOSC_64 and FRC. You should refer to your
particular device datasheet for further information.
Set the ADC conversion time

[rmteo]

That did it. Thanks, Jon.