Software ADC Comparator?

[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!