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Voltage jumps when USB plugged in. (help)
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Voltage jumps when USB plugged in. (help)

by terpDriver on Mon Oct 24, 2005 2:23 pm

I'm troubleshooting my non-working in-progress minty number 2. I've got the firmware loaded and USB subsystem implemented.

When I connect the battery and flip the power switch everything that is supposed to get +3.3V gets it. But as soon as I plug in the USB cable everything that is supposed to get +3.3V jumps up to +4.35V. It does this regardless of whether the power switch is in the On or Off position. I'm at the point where I should be able to see output in hyperterminal, but nothing comes out and I think this is part of the problem. I've poured over my solder connections under a scope and don't see any bridges.

Any suggestions? Ladyada?
terpDriver
 
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Joined: Wed Apr 27, 2005 1:00 pm

Re: Voltage jumps when USB plugged in. (help)

by Guest on Tue Oct 25, 2005 9:58 pm

terpDriver wrote:It does this regardless of whether the power switch is in the On or Off position.

I've poured over my solder connections under a scope and don't see any bridges.


Sure sounds like a short or a low resistance connection. Check the +5V (USB pwr) and the +3V3 pwr with an ohm-meter or a continuity tester.

Try tracing between the tracks with a toothpick or similar, you can't always see the short.
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