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Friday, November 18th, 2005

Time Event
USB gender changer and a warning about kernel summit gifts (aka d-link DWL-6730AP)
Week ago, I went shopping for a cable that would enable me to use sharp zaurus C3000 (aka spitz) as an usb host. I went to a (very strange) shop, and they did not have cable I needed, but they did have "usb gender changer". Basically two usb female connectors, connected. I thought "this can not work", but bought it anyway -- it was $1, and I could find uses for that one.

In fact it *does* work, but it is *very* incorrect. Current software for spitz ignores type of cable, and just provides usb host (and power!) even if cable does not have pins connected to indicate it is host. (That is dangerous, btw; don't plug in zaurus into PC with host modules loaded, not on 2.6.X).

Then I played a bit, and found out that zaurus provides enough power to charge t68i, but not enough power to power d-link access point. I experimented a bit, trying to power access point from 4xAA, but it did not seem to work. (AP is behaving strangely, anyway; if you plug/unplug it too fast, it appears to get confused).

I had strange feeling in my finger tip -- there's a metal surface on zaurus, and it should have been smooth. But my fingers suggested otherwise... on left part of it. I tried it with DC voltmeter, but found nothing. I thought to myself "vibrations from microdrive", and turned zaurus off. Did not help. Unplugged usb network card. Vibrations went away. Ouch. Plugged it back in, and this time voltmeter in AC 600V range... measured 80V. Okay, in AC 10V range, it measured 3V or so, so the power source is *very* weak and not too dangerous, but at least I know I was not dreaming.

So be careful with this thing. Apparently its power supply (jenec technology CO., model JTA0402D-A) puts something like 80V on its DC output lines :-( and access point happily passes it over ethernet cable. It is mostly harmless for humans, but I guess some equipment might care, and it is probably enough to generate radio interference.

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