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Old Jun 27, 2011, 07:36 PM
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utx
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Joined Apr 2011
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Quote:
Originally Posted by Paxman View Post
I think this is very interesting! I checked out your site and Im waiting for you to do some more finds on this matter. Please keep us updated!
Today I tried to trace the pin wires from the removed 0R resistor. I supposed that there is a resistor voltage divisor that converts the voltage to the 3.3V or lower levels of the processor, and changing the divisor I would be able to detect 3V on D+ instead of 5V on pin 1. I did not find any such part. It seems that the pin is connected to the semi-through hole and wired in one of internal layers of the PCB directly to the processor. It makes sense, but it complicates the modification.

Now I have a pin where I can control the camera behavior (left pin of the removed 0R on the image).

If I connect more than 4.3V there, idle camera switches to the mass storage mode (touch, release, and LED goes down exactly as it does after computer USB cable removal). If I connect 4.1V or more, camera stays in normal mode. (It explains, why the camera often leaves webcam or mass storage mode with a thin USB cable.)

So basically I would need to build a circuit that detects 3V bias voltage on the D+ line. When it is present, I should connect the pin to 5V, otherwise keep it open. Guessing that RC filter and open collector repeater may provide such function.

Maybe there is a better way to do it, but not having the main chip datasheet and the firmware source code, it is impossible to find it.
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