12F675 compare voltage help.

[geckogrotto]

I am trying to figure out how to use a 12F675 to compare voltage.
This will eventually be used to meaure a current load.

I am sending the output to serial and checking it via hyperterm just so I can see whats going on.

I have the chip connected like this.
1 + 3
2 NC
3 NC
4 NC
5 NC
6 pin2 serial.
7 testing connected to ground/pos/nothing.
8 ground and serial ground.

Here is my code most copied off this forum.

@ __CONFIG _INTRC_OSC_NOCLKOUT & _WDT_ON & _PWRTE_ON & _MCLRE_OFF & _BODEN_ON
    ' Internal Oscillator
    ' Enable watch dog timer
    ' Enable power up timer
    ' Disable MCLR pin
    ' Enable brown out detect

DEFINE OSCCAL_1K 1
INCLUDE "modedefs.bas"
CMCON = 7 ' turn off analog comparator
DEFINE OSC          4
DEFINE ADC_BITS     10  '10 BIT A/D CONVERSION RESULT
DEFINE ADC_CLOCK    3   'INTERNAL A/D RC CLOCK
DEFINE ADC_SAMPLEUS 50  'SET SAMPLE TIME IN MICROSECONDS
adval0  VAR WORD		'Create adval0 to store result

TRISIO = %000001        ' Set GSIO 0 & 3 TO INPUTS, others to OUTPUT
ANSEL.0 = 1             ' Set GSIO 0 to ANALOG
ADCON0.7 = 1	        ' Right Justify for 10-bit
I var byte







Pause 2000 


loop:
    ADCIN 0, ADVAL0         ' Read A/D channel 0            
    SerOut GPIO.1,N2400,["Result ",#adval0,13,10]

Pause 200
GoTo loop

When I have pin 7 connected to ground.
I get all 0's
When I have pin 7 connected to +
I get Result 1020
When I disconnect 7 from + I get Result 600 and it slowly goes down to 113 to 140.

Can someone explain to me what this is telling me?

[dhouston]

The ADC is 10-bits so the highest possible reading is 1023. Your 1020 indicates 3V (if that's your Vcc).

The 600 that fades indicates the ADC input is floating.

The 0 reading indicates the 0V.

[geckogrotto]

Ok thanks that helps but what does it mean its floating?

That mean the VCC is floating or when the ADC is connected to nothing its floating?

[dhouston]

The ADC input is floating and the reading is meaningless if it has no connection.

[geckogrotto]

Thank you very much.

[geckogrotto]

I am stuck again.

I multiply by 1000 to shift where the decimal will be.
The problem is my first calculation is
1022*1000 comes out 38960 instead of 1022000 How do I keep my whole number?


I tried this as well
dummy VAR WORD
adval0=1019
dummy = adval0*1000*3
adval0 = div32 1023


Gives me 111... Should be giving me 2988 or something...