Andrew Warren wrote:
>
> Jim Dolson <PICLIST@MITVMA.MIT.EDU> wrote:
>
> > I just ordered a DS1669 (PIC controllable pot) to adjust the
> > contrast on an LCD panel under PIC control.  I'm always interested
> > in reducing the parts count.  How would I adjust the contrast
> > using PWM?
>
>     It's pretty simple, Jim:
>
>     1.  Generate a PWM signal.  If your PIC has a hardware PWM
>     generator, great... If not, do it in software.  Make the PWM
>     frequency as high as possible.

1a. And if you can't make the PWM frequency very high, then consider
bursts of pulse width modulated pulses, where a "burst" may only be a
single PWM cycle. The trick is that while your not PWMing (is that
one or two ems?) the PWM output is reprogrammed as an input and
consequently a high impedance (i.e. no load on your RC filter).


Scott