Originally Posted by utx
I am now able to charge with a standard USB charger and record at once with my V2 camera! Just a small hardware modification (one 0R resistor removal) was needed: http://www.penguin.cz/~utx/hardware/...e_modification
The current camera circuit switches to mass storage or webcam mode whenever power supply appears on pin 1 of the USB connector. I plan to do more experiments and change the circuit to switch to USB mass storage or webcam mode only if USB data lines are wired to a real USB host. It is not so elegant as firmware change, but my camera would be fully charged after car ride recording aswell.
After this first step my camera never switches to USB mass storage nor webcam modes.
Incredible detective work. Very, very interesting
Originally Posted by utx
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.
. Thank you very much for your clear and precise explanations, and the excellent picture. I'm now seriously considering removing the resistor on my own camera.
Unfortunately, although basically very simple, this modification can't be done by the majority of people reading this thread because of the tiny circuitry and lack of equipment. For me it would be challenging because of my no-longer-so-good eyesight and clumsy fingers
Have you considered (mis)using the "Reset" button as a helping hand? This button doesn't have much use as it is. I know this would not be an elegant solution, but maybe easier than building a small smt board/wiring harness to monitor the data line(s).
Anyway, please do keep us informed if/when you find something new.