1 Reply Latest reply on Mar 8, 2011 8:35 PM by userc_45579

    Analog Inputs Strangeness

      I'm seeing something very strange with the analog inputs on J2/J3 on our Cypress IO board.  I have a potentiometer wired so that Pin 1 (VDDIO) is one one side of the pot and pin 14 (GND) is on the other side of the pot.  Pin2/P0_0/AI1 is connected to the potentiometer wiper.  When I move the wiper, AI1 is steady at about 50%, but _all_ the other analog inputs (AI2-AI8) follow the potentiometer.  When I attach the wiper to AI3, AI1-AI3 are steady and AI4-AI8 follow the wiper.  I've put a volt meter on the wiper and it's acting exactly as I'd expect.  I suspect I'm mis-wiring something; but what? 


      What am I doing wrong?  I just noticed that digital 15/16 mention analog comparator for analog out.  Does it get used for analog in also?  If so, do I need to gound it


      Here's some other anticipated answers: (1) I'm watching this in the driver station software not our software. (2) I'm setting the board up in enhanced IO mode.  (3) I flashed the board with the V2 hex file.  (4) I've borrowed a second board from a rookie team we are mentoring and saw the exact same behaviour on that board. (5) J1 and J4 are jumpered for 3.3V. (6) all 16 digital ports are configured for pulled down input.


      Thanks in advance


      Michael Andrews, FIRST Team 281