I have just bought an iRiver H340. It can be charged using a USB connector. I also have a Garmin Etrex GPS, which came with an in car power supply with exactly the same USB connector. My question is: can I use this to charge my iRiver? The voltage is the same (5V) for both, and I would assume USB connectors use a standard protocol so polarity wouldn't be a problem, but wondered whether anyone out there knew for sure?