> One example is using a capacitor and resistor on a 18F84 input pin to
> create an A/D converter. The cap will take a different amount of time to
> charge depending upon the current, which depends upon the voltage because
> of the resistor. This is not that accurate(temperature variability, etc.)
> and requires an internal logarithmic algorithm to get the optimum
accuracy,
> but it is a cheap, neat little solution. Other examples would be a
circuit
> to rectify,filter, amplify, and limit the output of a mic so that a PIC
> could tell if someone was talking or not. The moral of the story: most of
> the time an A/D is not needed and you can use a 16C/F84

I'm working on connecting temp probesto a 16C84.  One idea is to use a
voltage controller oscillator and connect it to an I/O pin and determine
the timing. Use an analog switch to multiplex the input and go through
timing a high and low reference voltage to compensate for any temperature
drift, etc. Perhaps there is an integrated A/D converter out there doing
all the already?

Regards,
Adi