Re: DSPIC33CK ADC Configuration help
In addition to the datasheet you should really read DS70005213, the "12-Bit High-Speed, Multiple SARs A/D Converter (ADC) FRM", which is intended to give generalized information while the datasheet gives the device-specific ones.
Yours has gotten a total of 13 ADTRIG?L/H registers. (The 'x' and 'n' wildcards seem to be somewhat inconsistently within the docs - or I do not understand the scheme.) As the ADTRIG.. registers are assined to analog input channels (not ADC cores), these 13 registers could support up to 26 analog channels (19 external plus 2 internal channels available).
Details are in the FRM. I haven't yet used a CK/CH device. Anyway, I assume that once you've got the concept of triggering channel conversions (vs. selecting an input by writing some value to an input mux register), the rest will not be too difficult.
And no - x/n has little to nothing to do with the DAC core involved in the conversion.
PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)