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Subject: RE: stupid question
From: Nielsen Linus (ext) (
Date: 2002-08-19

> I am assuming that the serial line can be configured from
> software to be a simple digital input, which is bi-directional.

Yes it is.

> If this is the case, can we do the following:
> Usually have it set as an output, with 1 (+3.3v) on it.
> Connect a capacitor across it and ground, to store some 'juice'
> Use a simple push-to-make switch to ground it through a
> potential divider
> Each (say) 1/100s we could flip the digital line to an input,
> and read it.
> If its 0, the switch is down, if its 1, the switch is not down
> Bingo! we have an input, with just a couple of passive
> components, and no battary

Sounds feasible, yes.

> Can someone who has studied the schematics/ knows the SH2
> processor tell me if this is possible?

I can't see a reason why it shouldn't work.


Page was last modified "Jan 10 2012" The Rockbox Crew