Hi Bruce,

> Sorry if this has been discussed before, but I'd like to try to emulate the
> technique which Timex uses, wherein the wearer holds their watch up to the
> PC screen, which flashes, transferring data.  Basic visible light comm seems
> hard enough to me; most likely the watch has a blue light PIN diode or some
> such; but I'm REALLY ignorant about video; are there tricky things to
> consider re scan rates, etc.?

The Timex Datalink watches use an ordinary visible light phototransistor (albeit
followed by a tricky filter). And there's nothing magic with the light: you can
even download to the watch using an ordinary red LED. It is standard RS-232:
light=0, no light=1. Just watch the bitlengths. If you want to do it with video,
that's where the hard part comes in. You need full control over the video
controller in order to produce the required timing (that's why it can't be done
on a Mac, where the OS cannot be worked around).

By the way, I used to work for Timex and was involved in designing the watch.

/Michael
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