Analog to digital conversion

[Guest]

I am trying to read the analog voltage on pin A1. Using the development board, I modified example 7 from the book

setup_adc_ports( RA0_ANALOG );
setup_adc( ADC_CLOCK_INTERNAL );
set_adc_channel( 0 );

to use ( RA1_ANALOG ) instead, but the compiler gave me the error "Undefined identifier RA1_ANALOG". What am I doing wrong?

[Ttelmah]

First, what chip?.
Now look at the data sheet for the chip. What 'patterns' of analog inputs a supported?. Gnerally, on most chips, you cannot have RA1, as analog on it's own. The patterns normally run something like:
AN0
AN0+AN1+AN3
etc.

Hence there is no 'RA1_ANALOG' definition, since the chip does not support just having this pin as an analog input....

Best Wishes

[Guest]

Thanks for the quick reply!

Its the PIC18F452. I've got the data sheet pdf in front of me, looking at section 17 (A-D Conversion) I haven't found what combinations are allowed yet, but the one you suggested seems to work OK. Thanks :-)

[jfk1965]

Look in the PICC/ devices folder and find the 18F452.h file and scroll down to the A/D section you will see all the valid options for that chip.

JFK

[Guest]

Ah yes, there they all are - loads of options.

Thanks!