ADC problem

[NacNud]

Hello,

First I want to say that this is a nice forum finding solutions for PBP.

Here is my queston about an Analog to digital conversion.
I want to put an conversion in the variable word_temp_int, but this ain't seem to work. Every result of the AD conversion is 0.
Using a PIC16F870.

This code is in my interrupt routine, the routine is 500 ms. The varaiable word_wachttijd_aantal is decreased with every interrupt.

if (word_wachttijd_aantal == 12) and (byte_status == 1) then
   adcon0.0 = 1                            ' AD converter on
endif
if (word_wachttijd_aantal == 11) and (byte_status == 1) then
   word_pot_adc = 0                     ' reset value potmeter
   adcon0.2 = 1                         ' start AD conversion
endif                
if (word_wachttijd_aantal < 11) and (byte_status == 1) then
   if adcon0.2 == 0 then                   ' test AD conversion ready
      word_temp_int.highbyte = ADRESH      ' store AD value
      word_temp_int.lowbyte = ADRESL       ' store AD value
      word_pot_adc = word_pot_adc * 9      ' some calculations
      word_pot_adc = word_pot_adc + word_temp_int
      word_pot_adc = word_pot_adc / 10
   endif
   adcon0.2 = 1                            ' start new AD conversion
endif

The AD converter is put on when word_wachttijd_aantal is equal to 12.
500 ms later the AD converter is started when word_wachttijd_aantal is equal to 11.
500 ms later the AD converter is stored in word_pot_adc because word_wachttijd_aantal is less than 11 and adscon0.2 is equal to 0 a long time ago.
After the AD value is stored in word_pot_adc a new AD conversion is started.

If I put de code untherneath here at the same place it works fine.

test:
   adcon0.0 = 1                            ' AD converter on
   pause 500                               ' wait 500ms is
   adcon0.2 = 1                            ' start AD conversion
ADC:	
   pause 5                                 ' wait 5ms aquisition time
   if adcon0.2 = 1 Then ADC                ' test if AD conversie is ready             
   word_pot_adc.highbyte = ADRESH          ' store AD value
   word_pot_adc.lowbyte = ADRESL
   adcon0.0 = 0                            ' AD converter off
goto test

[mister_e]

what about if you put an PAUSE 50 after starting the analog to digital conversion. This will give the PIC enough time to convert and store it to your var.

BTW wich PIC are you using ?

if nothing work, can you post/attach your whole code?

[NacNud]

I have found the answer myself. The if statements where more than 4 levels deep. Thx mister_e for your reply.

[mister_e]

I have found the answer myself. The if statements where more than 4 levels deep

kinda, but look a this part of your code really closer

if (word_wachttijd_aantal < 11) and (byte_status == 1) then
   if adcon0.2 == 0 then                   ' test AD conversion ready
      word_temp_int.highbyte = ADRESH      ' store AD value
      word_temp_int.lowbyte = ADRESL       ' store AD value
      word_pot_adc = word_pot_adc * 9      ' some calculations
      word_pot_adc = word_pot_adc + word_temp_int
      word_pot_adc = word_pot_adc / 10
   endif
   adcon0.2 = 1                            ' start new AD conversion
endif

in clear if you A/D conversion is not ready you begin a new one...
Simple to modify...

if (word_wachttijd_aantal < 11) and (byte_status == 1) then
   while ADCON0.2    'wait until AD conversion is ready
          pause 5
   Wend
      word_temp_int.highbyte = ADRESH      ' store AD value
      word_temp_int.lowbyte = ADRESL       ' store AD value
      word_pot_adc = word_pot_adc * 9      ' some calculations
      word_pot_adc = word_pot_adc + word_temp_int
      word_pot_adc = word_pot_adc / 10
   adcon0.2 = 1                            ' start new AD conversion
endif

IF THEN statement don't use stacks... SO you can use as many level you want... SUBs use stacks