At 12:25 PM 1/7/98 -0500, you wrote:
>----------
Walter,

I like the approach.  Is there any code examples that do this?

>
>           --------------|   Output Bit
>          |                 |
>         /  Rh            |
>         \                  |
>          |--------------|   Vin Sense bit
>         /         |        |
>         \  Rl === C   |
>          |        |        |
>           -------
>              |
>            GND
>
>
>    Vin the sense bit is at the threshold of the gate going into the
>    micro controller. Rh and Rl are the two resistors parts of the POT
>    The output bit is PWM by software to act like a variable voltage
>    for the resistor chain.
>                 Rl                  Th
>   Vin = -------------- *  ------------ * K
>             Rl  + Rh         Th  + Tl
>
>   "Th"  is the high time of the output bit and "Tl" is the low time of the
>
>   output bit. The software to measure the pot position toggles the
>   output bit to keep the Vin at the gate threshold. Solving the above
>   equation will show that there is a direct relationship between the
>   software PWM times and the pot position.
>
>   Practical implementations will have two fixed value resistors on
>   each end of the POT so the POT will operate over its entire range.
>   The C value is non critical. It is only used for filtering.
>
>
>Walter Bankls
>
>