TONY NIXON 54964 wrote:
> Pretty big question :-)

Answer: yes.

For the locomotive model driver chip, I'd use a trim-pot.  A multi-turn
pot would be good.  Using the presumably 5v regulated supply on the
circuit would be the most stable, without having to add a voltage
reference.  I'd run the A/D in the way you described, and have it read
at two times;

1)  at reset,
2)  on seeing a continually grounded track data input line.

While the track data is grounded, I would have the chip read the value,
then convert it to RS-232 serial 2400 baud and emit it on one of the
pins used for controlling the locomotive lights.  Continually.

So the procedure for setting the identification becomes;

a)  ground the track data input line,
b)  connect a PC to the RS-232 serial output,
c)  apply power to the chip,
d)  watching the ID displayed on the PC, adjust the trim-pot to be
    midway between the thresholds of the desired ID,
e)  apply significant other's nail polish to trim-pot.

Some temperature stablisation may be required.  ;-}

--
James Cameron                              (james.cameron@digital.com)
Digital Equipment Corporation (Australia) Pty. Ltd. A.C.N. 000 446 800