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July 16, 2008

iPhone 3G Firewire Charging Adapter

Update: CableJive will be selling an iPhone 3G Charge Converter starting around the end of August or early September.

Lots of folks are looking for something to fix the fact that their 3G iPhone doesn't work with existing iPod/iPhone docking devices. Apple didn't tell folks prior to the iPhone 3G release (including those in the "Made for iPod" program, my sources say) that they were disabling the ability for the iPhone to be charged using the 12V Firewire (on pins 19 & 20 of the Apple connector). Many accessories rely on this for powering the iPod/iPhone. To be fair, Apple has been pushing USB for some time, with some warnings to inside folks.

As an Apple activist and iPod/iPhone accessory hobbyist I've gotten a dozen or so emails about this problem. Folks want a solution that will let them plug their 3G iPhone into a device that provides Firewire power and have it work.

Conceptually, this isn't too difficult. I've made something for the Bose SoundDock, which took the 12V from the Firewire, reduced it to 3.3V to provide power back to the device to trick it into thinking an iPod was connected.

The iPhone 3G Firewire Charging Adapter is a slight derivation from this. The idea is to take the 12V from the Firewire pins (19 & 20), use a set of resistors to reduce the voltage to 5V, and provide that on pin 23 (ensuring ground is also sent to pin 16). Thus the female side of the adapter gets 12V on the Firewire pins, but the male end of the adapter outputs 5V on the USB pins.

Having made custom iPod/iPhone cables in the past I'm familiar with the amount of labor that goes into making this kind of thing from raw parts. For all the folks who expressed interest in the dock extender I hacked up, I (and a small team) made them for anyone willing to pony up $65 to cover the parts and the labor (a price that shocked some, but was no sweat for others).

I really don't have the time, but I can't resist throwing this idea out there to see what other folks are thinking.

Update: CableJive will be selling an iPhone 3G Charge Converter starting around the end of August or early September.

Posted by mike at July 16, 2008 7:57 AM