This is a jal procedure for reading the AD module of the 12F675. I
think is self explanatory. Try to convert it in C and will (probably)
work.

 const bit ref_extern    = high
 const bit ref_vdd       = low
 const bit left_justify  = high
 const bit right_justify = low

 procedure one_ch_ad_read ( byte in channel, bit in ref, bit in justify ) is
; result in adresh and adresl,
; channel = 0...3, ref=high means external reference, justify=high
means left justify
   var byte local
   if    channel == 0 then local = 0b_0000_0001
   elsif channel == 1 then local = 0b_0000_0010
   elsif channel == 2 then local = 0b_0000_0100
   elsif channel == 3 then local = 0b_0000_1000
   end if
   asm bsf _rp0    ; set bank1
   ansel = ( 0b_0001_0000 + local ) ; fosc/8, internal 4MHz clock
   asm bcf _rp0    ; set bank0
   channel = channel << 2
   adcon0 = ( 0 + channel )
  if ref then
     asm bsf vcfg
  else asm bcf vcfg
  end if
  if justify then
      asm bcf adfm
  else asm bsf adfm
  end if

   asm bsf adon                    ; supply the ad module
   delay_10uS ( 1 )                ; wait the sampling time
   asm bsf go_done                 ; start the conversion
   while go_done loop end loop     ; wait for ad completion
 end procedure

usage:
one_ch_ad_read ( 0, ref_vdd, left_justify )
read the adresh and adresl


On 9/18/06, Shawn Wilton <black9@gmail.com> wrote:
> Yeah, I have tried this and the conversion never returns.  I block on the
> poll of the Go\Not Done bit and it never changes back to a zero indicating a
> successful conversion.
>
>
> On 9/18/06, Vasile Surducan <piclist9@gmail.com> wrote:
> >
> > There are two wais (at least) of using the AD module in PIC
> > microcontrollers.
> > First one is: set the AD channels and device operating frequency, turn
> > on the AD module, wait 20uS for aquisition time and wait untill the
> > GO/DONE bit is changing
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