Analog In for 16F88 with IR Sensor.

I'm having difficulty getting the following code to work. I have it wired such that the Sensor (QRE1113 Sparkfun) inputs to RA1/AN1, and outputs to a LED on RB4. I have verified the functionality with a digital signal (pushbutton), but cannot get it to work in Analog.

Even now, my push button works, using the following code, but the sensor does not. Using a Voltmeter, my sensor currently provides a range of about 1.7-4.6 Volts, so hopefully it should switch whenever it crosses 2.5.

I feel that it may be one or a combination of the following:

- Not Defining my Analog controls correctly / completely
- Not having a reference voltage (maybe?)
- Not understanding how to define 8 bit thresholds properly.

Any assistance appreciated, and thank you for your time,

Code:

---

'----------Variables------------
    x  var byte              ' Byte for potentiometer input     
'----------Initialization---------
 
    TRISB = %00000000
    TRISA = %00000010
   
    'DEFINE OSC 8        ' Sets the internal clock speed to 2 MHz             
    'OSCCON.4 = 1       
    'OSCCON.5 = 0                                               
    'OSCCON.6 = 1

    ANSEL = %00000010  ' Leaves AN1 in analog mode, all else digital.               
                                                                     
'--------Main Code--------                           
   
myloop:

    adcin 1, x                ' Read analog voltage on AN1 and
                              ' convert to 8-bit digital value
                              ' and store as x.   
    if x > %10000000 then
        PORTB.4 = 1
    endif
   
    if x < %00000111 then
        PORTB.4 = 0 
    endif 
 
goto myloop                  ' Go to loop label 

end

---

(newbe here)

Should that be High PORTB.4 and LOW PORTB.4?

I also don't see an ADCON1 being setup

Code:

---

if x > %10000000 then
        PORTB.4 = 1
    endif
   
    if x < %00000111 then
        PORTB.4 = 0 
    endif

---

There are two versions of the QRE1113 - one digital, one analog . Are you sure you have the analog version?

Quote:

---

Originally Posted by norohs

(newbe here)

Should that be High PORTB.4 and LOW PORTB.4?

I also don't see an ADCON1 being setup

Code:

---

if x > 000000 then
        PORTB.4 = 1
    endif
   
    if x < 000111 then
        PORTB.4 = 0 
    endif

---

---

You're correct, for my purposes, the high / low settings should be reversed. I'm trying to read up more on how the ADConverter works, to get this circuit working. There are lots of examples of using it with a LCD on RA4, but I can't find anything more.. general.

And yes - I'm sure I have the Analog version. Also, looks like you can't edit old posts, I meant to set my thresholds at 128 on both sides, but forgot to edit it before copying in. The low threshold should be set at 128, not 7.

I'm getting the impression that I need the following things for my 16F88

Code:

---

ADCON1.7 = 1

---

or

Code:

---

DEFINE ADC_BITS 10

---

Do I need both of these if I only want my A/D to be 8 bits? (IE: ADC_BITS 8)