ADC problems with a 16F1826 chip

Hello all
I'm trying to use a new chip to me, an 16f1826. I liked the idea of the 4.086 internal voltage reference. I wrote the test code below, trying to follow the datasheet. Unlike others, I've never had a problem using ADCIN so I am using it. The program compiles, loads and runs, but the display reads 00001, 00002 and 00003, depending on what my test pot is set to. Interestingly, it does correspond to 1, 2 and 3 volts input, but I'm assuming its coincidental since its a 10 bit register. The Microchip errata says that in my silicon version there is sometimes a flaw in the ADC circuit such that the "done" bit never comes true but I'm assuming thats not the problem because it does change its value and updates each cycle through. Any thoughts or comments would be appreciated.

Take care

Alec

Code:

---

'****************************************************************
'*  Name    : 16f1826_test                                      *
'*  Author  : alec noble                                        *
'*  Notice  : Copyright (c) 2012 alec noble                    *
'*          : All Rights Reserved                              *
'*  Date    : 8/31/2012                                        *
'*  Version : 1.0                                              *
'*  Notes  :                                                  *
'*          :                                                  *
'****************************************************************
 #CONFIG
  __config _CONFIG1, _FOSC_INTOSC & _MCLRE_ON & _CLKOUTEN_OFF
  __config _CONFIG2, _PLLEN_OFF & _LVP_OFF

#ENDCONFIG

OSCCON = %01111010          '16 mhz internal clock, PLL off

DEFINE OSC 16

'define adc_bits = 10

TRISA = %00000001          'RA0 input, all others output
trisb = %00000001

FVRCON = %11000011          'Fixed voltage reference on, comparator and output off, set to 4.096

ANSELA = 1                  'AN0 analog, all others digital
ANSELB = 0                  'all port B digital
ADCON1 = %11100011          'right justified, clock = fosc/64, neg ref = Vss, pos ref = FVR

ADC    var word
txpin  var portb.0

ADC = 0

Pause 500                  ' let everything stabilize

SEROUT2 txpin, 84, [24]    'turn serial LCD on

main:
    ADCIN 0, adc
    SEROUT2 txpin, 84, [12]
    PAUSE 5
    SEROUT2 txpin, 84, [128,  dec5 adc]
    pause 250
    goto main

---

Just change your define to all uppercase and no = sign..

define ADC_BITS 10

Without the correct define, PBP is still using 8-bits, and all you see are the top 2 bits when it's right justified (0-3).

Damn!!!

Thanks Darrell - ebeer to you:biggrin: