12F1840 ADCIN troubles, help needed :(

[CuriousOne]

Hello.

I'm trying to use ADCIN on 12F1840, here's the code:

;----[12F1840 Hardware Configuration]-------------------------------------------
#IF __PROCESSOR__ = "12F1840"
  #DEFINE MCU_FOUND 1
#CONFIG
cfg1 = _FOSC_INTOSC           ; INTOSC oscillator: I/O function on CLKIN pin
cfg1&= _WDTE_OFF              ; WDT disabled
cfg1&= _PWRTE_OFF             ; PWRT disabled
cfg1&= _MCLRE_OFF             ; MCLR/VPP pin function is digital input
cfg1&= _CP_OFF                ; Program memory code protection is disabled
cfg1&= _CPD_OFF               ; Data memory code protection is disabled
cfg1&= _BOREN_ON              ; Brown-out Reset enabled
cfg1&= _CLKOUTEN_OFF          ; CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin
cfg1&= _IESO_ON               ; Internal/External Switchover mode is enabled
cfg1&= _FCMEN_ON              ; Fail-Safe Clock Monitor is enabled
  __CONFIG _CONFIG1, cfg1

cfg2 = _WRT_OFF               ; Write protection off
cfg2&= _PLLEN_OFF             ; 4x PLL disabled
cfg2&= _STVREN_ON             ; Stack Overflow or Underflow will cause a Reset
cfg2&= _BORV_19               ; Brown-out Reset Voltage (Vbor), low trip point selected.
cfg2&= _LVP_OFF               ; High-voltage on MCLR/VPP must be used for programming
  __CONFIG _CONFIG2, cfg2

#ENDCONFIG

#ENDIF

;----[Verify Configs have been specified for Selected Processor]----------------
;       Note: Only include this routine once, after all #CONFIG blocks
#IFNDEF MCU_FOUND
  #ERROR "No CONFIGs found for [" + __PROCESSOR__ +"]"
#ENDIF


OSCCON = %11110000  'SET INTOSC TO 32MHZ

TRISA=%00110000 'set LATAA.4 as input
ANSELA=%00010000 'set LATAA.4 as analog
ADCON0=%00001101  'ENABLE AND CONFIGURE ADC
ADCON1=%11100011   'JUSTIFY
CM1CON0=%00000000   'DISABLE COMPARATORS

DEFINE OSC 32
DEFINE ADC_BITS 10
DEFINE ADC_SAMPLEUS 50
DEFINE ADC_CLOCK 3
VOLTAGE VAR WORD
SHEMAVALI VAR LATA.4
LED VAR LATA.2


'PACUKA:
'HIGH LED
'PAUSE 200
'LOW LED
'PAUSE 200
'GOTO PACUKA

CIKLURI:
ADCIN 3,VOLTAGE
IF VOLTAGE=>1023 THEN 
HIGH LED
else
low led
endif
pause 5
GOTO CIKLURI

The problem is that VOLTAGE variable always reads 1024, if input is not connected to ground.

Any ideas?

[grahamg]

Firstly ADCON1=%11100011 'JUSTIFY statement is conflicting with DEFINE ADC_CLOCK 3.
Secondly IF VOLTAGE=>1023 THEN statement can never be greater than 1023. DEFINE ADC_BITS 10 means maximum value of voltage =1023.

[CuriousOne]

well that IF is just experiment
In real life, ADCIN returns 0 if input is grounded, if any other voltage is applied, it returns 1023.

[CuriousOne]

Found the problem!

I was using Fixed internal voltage reference, but was not enabling it at all.

added

FVRCON=%11011111

and now it works OK!

[CuriousOne]

Well, troubles continue.

I've built a following circuitry. 10K resistor goes to LATA.2 pin and goes then to gnd.
100k variable pot is connected one end to VCC, another to LATA.2
LED is connected to GND via 1k resistor from LATA.1

Wiring is 100% checked and corrected for shorts, misswire, etc.

The code is as follows:

OSCCON = %11110000  'SET INTOSC TO 32MHZ
TRISA=%00110000 'set PORt as input
'ANSELA=%00010101 'set PORTA.4 as analog
ADCON0=%00001111  'ENABLE AND CONFIGURE ADC
ADCON1=%11000011   'JUSTIFY
FVRCON=%11011111 'VREF ENABLE & set at 4.096v
WPUA=%00000000 'pull up disable
'CM1CON0=%00000000   'DISABLE COMPARATORS

DEFINE OSC 32
DEFINE ADC_BITS 10
DEFINE ADC_SAMPLEUS 50
DEFINE ADC_CLOCK 3
VOLT VAR WORD
LED VAR LATA.1

greater:
adcin 2,volt
high led
pause 1
low led
pause volt/10
goto greater

This code should do a simple thing - vary LED brightness according to pot setting. And sure it does, but the problem is that it works in very narrow range, because port sinks huge amount of current - up to 25mA via that pin. So say to achieve 2.5v on the pin, the pot resistance should be set somewhere to 40 ohms. I think this is not correct, right?

Also I found a strange thing - if I set TRISA=%00110010, which means to set LATA.2 as input, the code does not works at all, but it also stops consuming current on that pin. What can be the reason?

[mark_s]

Well, troubles continue.

Also I found a strange thing - if I set TRISA=%00110010, which means to set LATA.2 as input, the code does not works at all, but it also stops consuming current on that pin. What can be the reason?

I think you have set porta.1 to input and not porta.2

This sets PORTA.2 as input

%00110100

Not sure about your other problems