referance voltage for adc

on the BV502 can I set an external referace voltage for the ADC or do I have to use the fixed votage, and if so what is that fixed voltage??
Thanks

By default the ADC voltage is fixed at 3.3V. If using rookie then it is simply a case of adc_init(channel) and adc_get(channel) to use.

All the pins are available so it is possible to use a different source, you will need to consult the PIC32MX170 data sheet.