Re: What is the quintessential Apple II?

["mdj" <mdj.mdj@gmail.com>]

Roger Johnstone wrote:

> A customer recently brought in a faulty timer board they wanted
> replicated. All it had to do was switch on a load once every 24 hours
> for a short time which was adjustable. The board looked overly
> complicated so I traced out the circuit to see exactly what it was doing.
> The original designer had used an 8-pin micro for the 24 hour timer, and
> a 555 timer IC with a variable resistor for the adjustable time. The
> best of both worlds!
>
> We made a new board with a single 8-pin micro on it which performed both
> functions. The resistor for the variable time is read by the micro
> charging up a capacitor, then timing how long it takes to discharge it
> through the resistor. I'm surprised no-one thought of doing that before ;
> o)

I must admit the smallest uC I've used is a 16 pin device which had the
benefit of 3 analog inputs, so a pot wired as a voltage divider is the
only hardware required.

Of course, if all I had left was a digital input, I'd use the same
technique you did, or see other post alternative technique which works
a lot better when the sample rate needs to be constant, or even just
relatively high.

Matt