Re: Wireless joystick for the Apple II?

[larwe <zwsdotcom@gmail.com>]

On Sep 25, 1:06 am, "Michael J. Mahon" <mjma...@aol.com> wrote:

> The servo PWM pulses vary from about 1 ms. to about 2 ms., so you'd need
> measure the duration of each pulse (just filtering would probably slow
> down response too much) and convert that timing variation into a
> resistance variation of a few ohms to about 150kOhms (an FET would be

I don't think a controllable resistance is necessary, IIRC the Apple's
analog joy/pot inputs work by measuring the time taken to charge a cap
from 0 to Vih from a V supplied by using the pot as a voltage divider
from Vcc. So a simple voltage source would work just as well.

DACs are quite rare on small micros (not unheard of but rare) - an
R-2R ladder would work, but one more usually gets "DAC" output from
these devices by PWMing.

It's conceptually simple but not just a matter of taking off the shelf
parts and wiring them together; definitely a weekend's worth of
tinkering and coding.