628 already have internal ref, not too good, low resolution,
you should have 10bits resolution with pwm but you'll have a lousy
comparation threshold detection even with externaly positive feedback on
the comparator. Try 12F675 or 16F870

regards,
Vasile
http://www.geocities.com/vsurducan


On Mon, 7 Oct 2002, Mike Singer wrote:

> > On Sun, 6 Oct 2002, Jeethu Rao wrote:
> > > Hi all,
> >  I need a cheap and dirty ADC with a 16f628,
> >  Scott's RC based ADC is a good option, but
> >  I think there is a way to use the Comparators
> >  And the PWM on board the f628 for it. I'm thinking
> >  Of making an RC low pass filter for the PWM output
> >  And using it for Ref. I should be able to get the
> >  Full 10bits accuracy of the PWM (atleast I think so).
> >  Is this doable or has anyone tried this?
>
> May be I'm missing something, but why not 16F870?
>
> PIC16F628   18LD  20MHZ 2K FLASH   $2.74
> PIC16F870   28LD  20MHZ 2K FLASH         $3.09
>
> Are extra pins a big trouble: ATtiny could be an answer.
>
>  Mike.
>
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