Hello,
1. If I configure 28X2 as "adcconfig 0101", and on VRef+ at external pin I set 4V, and on VRef- at external pin I set 1V (that difference is 3V), the difference will be read with "readadc" as all 255 levels from 1V to 4V (every level resolution= 11,7mV) or it will be read as only 204...