Software ADC Comparator?

[Jerson]

Ryan

You seem to be reading 3 diff adc ports. First of all, you have to tell us what is each one for any of the code I gave to make sense.

The code I gave wants only 1 adc port to sense the light intensity. So, the other 2 are redundant. And the code I gave should do exactly what you asked for.

Check your code. You seem to have got it diff from what I have given you.

in Pseudo code what I have sent you does this

if CurrentADC != PreviousADC
Output = high
Wait 1 second
Output = Low
PreviousADC = CurrentADC
endif

Jerson

[Ryan7777]

here is where i am now, and it still doesn't work, no matter.. also, if I were to set my current reading and previous readings equal, the next loop through would set them to what ever the ADC says at sample time anyway.. so it would be pointless wouldn't it?
PreviousADC = CurrentADC ?

@ DEVICE pic16F684, HS_OSC, WDT_OFF, PWRT_OFF, MCLR_ON, BOD_OFF, IESO_OFF, FCMEN_OFF

DEFINE OSC 20
DEFINE ADC_BITS 10
DEFINE ADC_CLOCK 2
DEFINE ADC_SAMPLEUS 11

CMCON0 = %00000111
VRCON = %00000000

ANSEL = %00110100

ADCON0.6 = 0
ADCON0.7 = 0

voltLevBf VAR WORD ' variable for first reading or "previous"
voltLevAf VAR WORD ' variable for second reading "current"
voltLevCk VAR WORD ' variable for holding the difference
threshHold VAR WORD ' variable for the threshold
timOut VAR WORD ' variable for holding the timeout

prgSel VAR PORTC.2 ' not in use yet
swtOut VAR PORTC.3 ' output to LED

CLEAR

PAUSE 1000


autoGainPrg:

ADCIN 2, voltLevBf ' sample voltage on ADC 2

PAUSEUS 12

ADCIN 4, threshHold ' get threshold from pot set up as volt. divider on ADC 4

PAUSEUS 12

ADCIN 2, voltLevAf ' sample voltage on ADC 2 again, to check for difference

PAUSEUS 12

IF lghtlevAf > lghtlevbf THEN ' IF the second reading is higher than the first,

voltLevCk = voltLevAf - voltLevBf ' subtract the first reading from the second to get the Dif.

IF voltLevCk > threshHold THEN ' IF there is a difference, and it is greater then threshold

HIGH swtOut ' set the LED high

PAUSE 60 ' pause for 60 mS

LOW swtOut

ADCIN 5, timOut ' check volt. div pot on ADC 5, use number as time out - 0 to 1023

PAUSEUS 12

PAUSE timOut ' Pause for the time out setting, determined by ADC 5

ENDIF

ENDIF

GOTO autoGainPrg:

[Ryan7777]

just to make sure the problem i need to solve is clear, i will explain what i want yet again.
I will not be monitoring a sine wave, the signal will not vary that often actually and will never go negative in relation to ground. but for the sake of an example, I will use sinewave.

Say that there is a sine wave, the frequency of which does not matter, that is 2 Vp-p.
This Sine wave is "floating" with its zero point at 2 volts above ground, making the lowest peak 1 volt, and the highest peak 3 volts. then we'll say my threshold is set at 1.5V.
When the sine wave reaches 1.5V above the 1 volt line (not ground!), it triggers a response from my circuit, or flashes the LED once, and then waits.
Where the sine wave is "floating" (again, floating, not peaking) doesn't matter, it will be anywhere between 0 and 5 volts and is out of my control, it is an independent circuit.
The PIC circuit only needs to trigger when there is a positive going change in voltage that exceeds a threshold that i will need to have control of. so therefore, the threshold has to follow the 1 volt ( or 2V or whatever!) line automatically, while i can vary the threshold level, it will always be in reference to the 1 volt line! not ground. please see my example.bmp
(and yes i know that if my threshold is 1.5 volts, and the signal zero reference exceeds 3.5, the threshold will be out of range, and that is fine because 1.5V is only an example.)

[Jerson]

Ryan

Now, I understand what you're trying to do. However, reading the adc like this hardly gives you anything worthwhile.

ADCIN 2, voltLevBf ' sample voltage on ADC 2
PAUSEUS 12
ADCIN 4, threshHold ' get threshold from pot set up as volt. divider on ADC 4
PAUSEUS 12
ADCIN 2, voltLevAf ' sample voltage on ADC 2 again, to check for difference
PAUSEUS 12

Why? The difference between the 2 samples on ADC 2 is just around 25uS. Is this what you really want??

On reading closely, I think you need to do this

'Find the minimum value
MinAdc var word         'I'm assuming the ADC to be 10bit or more
CurrAdc var word
Threshold var word
DelayVal  var word

while 1                                     ' loop forever
    ADCIN 2, CurrAdc                    ' current ADC reading
    ADCIN 4, Threshold                 ' threshold setting
    ADCIN 5, DelayVal                   ' delay setting
    if CurrAdc > MinAdc + Threshold then
           High Output
           pause DelayVal
           Low Output
           if CurrAdc <> MinAdc then  ' check if the current ADC value < Min ADC
             MinAdc = CurrAdc          ' and correct the MinADC value
           endif
    endif
wend

Does this do what you want?
Jerson

[Ryan7777]

I don't know yet, i'll have to give that code a shot, one thing i did figure out tho is that my justification was wrong, i should have had it set to right justify, and I should have saw that earlier! I used serout to spit out the ADC values and now everything looks like it should, but i'll have to do further testing.

Thanks again!