Paul Duffy wrote:

> Hi
> 
> I am using the 16F684 and want to read 2 different A/D inputs to set 2 different time delays in my widget.  I have 2 potentiometers, set up as voltage dividers, connected to the A/D inputs.  My attempts to read the A/D are failing.  Here is the relevant code snippet:
>   .....
>   .....
>    off = 0;
>    on = 0;
>    ansel = 0b0000011;          //select AN0, AN1 (pins 12, 13) as A/D inputs
>    adcon1 = 0b01010000;     //select 16*Tosc clock - gives TAD of 4uS 
>    adcon0 = 0b00000001;     //turn on A/D, select AN0 as input, don't start conversion
> 
>    while(1)                            //Main Loop - continuously update porta and portc.  
>         {
>         porta = off;                  //display via leds connected to available port pins
>         portc = on;                  //display via leds connected to available port pins
>     
>         adcon0 = 0b00000001;           //turn on A/D, select AN0 as input, don't start conversion
>         delay_ms(10);                      //delay each time through loop, 
>         set_bit(adcon0,1);                  //start a/d conversion
>         while (!test_bit(adcon0,1));      //wait for completion
>         on = adresh;                          //store on_time - AN0
>         if(on==0)on = on+1;                //ensures on_time !=0
>    
>         adcon0 = 0b00000101;           //Change the input to AN1, don't start conversion
>         delay_ms(10);                       //delay each time through loop, 
>         set_bit(adcon0,1);                 //start a/d conversion
>         while (!test_bit(adcon0,1));     //wait for completion
>         off = adresh;                         //store off_time - AN1
>         if(off==0)off = off+1;               //ensures off_time !=0
>         }
> 
> As it is, this does not work at all.  I see no change on the leds connected to portc or porta when I change the potentiometers.  If I remove one of the "adcon0=..." statements, then one of the potentiometers is read and displayed in both ports.  Depending on which of the 2 "adcon0=..." statements I delete, I can read either potentiometer.  How do I switch between the a/d inputs so that I can read both potentiometers?
> 
> Thanks in advance for any help.
> 
> Paul Duffy
> 

 >    set_bit(adcon0,1);                 //start a/d conversion
 >    while (!test_bit(adcon0,1));       //wait for completion

You have not "inverted" the test there ?
It shouldn't be "while (test_bit(adcon0,1));" ?

I might might have got the logic levels wrong though...

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist