[COLUG] OT: OneWire hardware hacking

[Ethan Dicks]

On Jan 3, 2008 6:29 AM, Josh <josh at globalherald.net> wrote:
> Mike Schoenborn asked about the timing of the device in question.  It is a
> DS1821...
>
> My timing was off before:
>
> The Pulse "low" time can range from 0.1-10 Microseconds
> The pulse "high" time seems to be able to range from 0.1 microseconds to
> infinity
> The pulse transition time must be less than 100 nanoseconds
>
> Pages 16 and 17 of this datasheet provide more details:
>
> http://datasheets.maxim-ic.com/en/ds/DS1821.pdf

I don't know of a way to get just a 555 and (a small number of )
discretes to do as you describe (issue exactly 16 pulses then shut
down), but perhaps a 555 coupled with a 4-bit counter (like a 74LS93)
and perhaps an external flip-flop to toggle the gate input on the 555
so that it powers up to allow pulses through until the counter wraps
around to 0, which toggles the flop and inhibits further pulsing until
a reset.

So... a 2-3 chip solution?

-ethan