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At 10:02 PM 3/31/00 -0600, John A. Craft wrote:
>I've seen it done with pre-packaged products, but how can I leach enough
>power from RS-232 to power a F876?

In a production design?

Look up the 232 spec, and find the minimum load spec. This will tell you
how much current each connected driver must be able to source. Also, note
that the drivers only have to develop 3V into this load.

Use the highest impedance for your receivers you can, and pocket the
change. :)
In real life, they will do better than spec, but that's all the energy you
can count on.
It's a lot like phone line powered devices, you can only count on 20mA, and
no particular voltage at all.

This is a good excersize for those who skimp on their 232 interfaces to run
through, as it helps illustrate that the "other guy" may need some of that
margin too :)
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