My girlfreind is right, I am a bonehead sometimes.  I was assuming it was an A/D
output.

Would a hardware solution work?  Use the input to pulse a RC circuit (2 resistors
and 1 cap).  Feed the cap voltage back to another input pin.  More pulses (1's) =
more voltage across the cap.  At some point you would have your digital high on the
2nd input pin.  Would make it easy to adjust your trip-point (if you need to do
that) on the fly but of course it uses more pins and external hardware.

Patrick J wrote:

> A/D ?!? I must be missing something here.. Not using any A/Ds...
>
> ----- Original Message -----
> Subject: Re: [PIC]:pic16F877... howto keep in range ?
>
> > Just use the upper byte of your A/D and throw the lower one away
> >
> > Patrick J wrote:
> >
> > > I have a sensor that gives output simular to this:
> > > empty: 000000100000010
> > > midfull: 011100011011101
> > > full: 11101111001111101
> > > As you can see I mostly get 1:s when the level is high.
> > > When empty, I get mostly 0:s when the sensor is polled.
> > > I want this sensor input to produce a thermostat-like output.
> > > ON until 'HOT' (or rather 'full')
> > > OFF until 'COLD' (or rather 'empty')
> > >
> > > My basic idea for this, is to poll the sensor and:
> > > if Sensor=1 then X=X+1
> > > if Sensor=0 then X=X-1
> > > Timeconstant: (exact timing, nor speed, is an issue)
> > > If Sensor=0, X will count down to min (LOW) in 3 secs
> > > If Sensor=1, X will count up to max (HIGH) in 3 secs
> > >
> > > A pic running at 4MHz polls the sensor at approx 80kHz, if the
> > > loop takes 50 cycles. 80000* 3sec gives X will be in the
> > > 0-240 000 range. 18 bits math.
> > >
> > > It would be more convenient to have a 0-255 range instead.
> > > 32 bits math is not fun. And takes up much ram for changable limits etc.
> > >
> > > I have a few ideas on howto do it:
> > > - divide X (32 bits) by 1024 and use that as new X (8 bits)
> > > - only add 1 when counted 1024 1:s. only sub 1 when counted 1024 0:s
> > > - some kind of (moving) average could be used ?
> > >
> > > My question is, is there a better/simpler way to keep X in a decent range ?
>
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