On 22/05/2011 19:09, Yigit Turgut wrote: >> How is the pot actually connected? You don't show it on your schematic. >> What voltage/value are you seeing? (as an aside, I thought the 2550 has >> a 10-bit ADC?) > Pot and 1.5v battery are connected to AN0 all in series.Ground of > battery is connected to ground of the circuit. In series? In that case you will always read ~+1.5V then. Can you show a schematic just to confirm what is connected to what? > That's correct it has 10bit ADC, I am using most significant 8bits of > it. I am just experimenting. > >> If I understand you right, it works okay with some voltage "directly" >> applied to the input, but not when you apply through the pot? > Yes that's correct. > >> I can't see any reason the pot wouldn't work too with the ends at >> Vdd/Vss and wiper to AN0, providing the voltage driving the pot is of a >> low enough impedance not to raise the total over whatever it is MC >> recommends (10K generally IIRC) - have you confirmed with a >> multimeter/scope the voltage is actually present and changing at the >> pin? (i.e. the pot isn't dodgy or you have an open circuit somewhere) > I confirmed that pot works by externally testing it with scope and > multimeter using the same source I apply (1.5V battery). > >> Also, your circuit doesn't show any power bypass caps in place. > There is a 220nF capacitor connected to VUSB (14) pin of PIC, sorry > didn't mention that. Yes, I saw that on the schematic, you will need a cap between Vdd and=20 Vss too though. The datasheet should have a recommended minimum=20 connection diagram for reference. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .