I am confuse

[mackrackit]

I think this chip has the comparators off on reset. I need to double check.

Thinking more along the lines of not reading both the high and low bytes of the 10 bit setup might be the problem???

[Acetronics2]

Hi, Dave

you're right ... I never trust in defaults ... ( overhead, yes ... but sleeping nights ...)

what about this one :

TRISA = %00001111

RA5/MCLR/VPP bit 5 ST Input, Master Clear (Reset) or programming voltage input.

I am using RA5 as my communication out to the LCD

...

Alain

[mackrackit]

Alan,

That would make the display act funny

[timseven]

Well, first I did was to change the out pin to the LCD (Sorry I was using RA6 not RA5) to PortB.1 as for the test only. Second, I changed ADC to 8 bits and it went to zero but refuse to read any change voltage so I set it to back to 10. I wonder how can I set the AD comparators off using ADCON0. I read the 16F88 spec sheet page 114 and I don’t find a way to turn those comparators off. Please advice.

[mackrackit]

http://www.picbasic.co.uk/forum/showthread.php?t=561
Worth reading.

[mackrackit]

I picked up the below method of reading the ADC here
http://www.rentron.com/PICX2.htm
I like it much better than ADCIN.

The below code is an example for reading ADC channel 0. Look at the example on the above link to add other channels.

It looks like a lot of stuff to do to read the ADC, pretty much what ADCIN does behind the scenes. This way you have control.
The "READ_AD" part is only needed once no matter how many channels you are reading (reusable).

Use your LCD or SERIAL to see what is happening. I have this running at 2400 baud. Works OK with the internal OSC for testing.

[color=#000000]    '16F88 ADC TEST  FOR CHANNEL 0
    DEFINE OSC 4           
    OSCCON = %01100000
    @ __config _CONFIG1, _INTRC_IO & _WDT_OFF & _LVP_OFF & _MCLR_OFF &_CP_OFF
    ANSEL = %00001111
    TRISA = %11111111
    CHAN0  VAR WORD   'VAR TO HOLD ADC0 READING
    START:
    HIGH PORTB.3    'HEART BEAT
    PAUSE 250
    LOW PORTB.3
    PAUSE 250
    'BELOW WILL SHOW WHAT THE ADRESH AND ADRESL REGISTER HOLDS
    SEROUT2 PORTB.2, 16780, ["ADRESH ",DEC ADRESH," ADRESL ",DEC ADRESL,$a,$d]
    PAUSE 50
    'BELOW SHOWS THE 10 BIT READING OF ADC0 IN VAR CHAN0
    SEROUT2 PORTB.2, 16780, ["CHAN0 ",DEC CHAN0,$a,$d]
    GOSUB ADC_0      'STARTS THE READING OF ADC CHANNEL 0
    GOTO START
    
    ADC_0:       'READ AN0
    ADCON1 = %10000000      'SET FOR 10 BIT
    ADCON0 = %00000001      'TURNS ADC ON
    GOSUB   READ_AD
    CHAN0.HighByte = ADRESH  'PLACES THE HIGH AND LOW BYTE
    CHAN0.LowByte  = ADRESL   'INTO VAR CHAN0
    RETURN
    
    READ_AD:   'DOES THE ADC CONVERSION
    PAUSE   50
    ADCON0.2 = 1
    PAUSE   50
    RETURN  

[Melanie]

You can actually improve on that Dave...

Instead of...

ADCON0.2=1
PAUSE 50
RETURN

... which makes the assumption that your ADC reading will complete in 50mS... well - suppose it didn't? And suppose it only took only 50uS then you've wasted a shed load of time!

So, rather than a hit or miss approach, nail it properly...

ADCON0.2=1
WHILE ADCON0.2=1:WEND
RETURN

To find out why I've done this, read the Datasheet description for pin ADCON0.2