iPod / iPhone Dock with Full Time Power
I'd like to add my iPhone 3G into my carputer, and have a few questions on the best way forward.
Here are my interests for this project:
1. Need to have USB 2.0 connection to carputer
2. Needs to charge iPhone while car / carputer is powered off.
(I frequently have to leave my phone in the car - want it to stay powered during the day to charge.)
This was possible with my Windows Mobile phone - it had a dock that had 2 USB mini connections - one for data and one for dedicated power.
So here's my question.
How do I do that for the iPhone.
Should I (Can I) simply hack a cable that will connect the data side of the USB to the carputer, while drawing power from a full-time 12v source in the car?
I believe that the iPod / iPhone can take 12v power from the Firewire connection.
I don't know however if you can mix and match connections (i.e. Data from USB 2.0, power from Firewire)
If I am required to only use one connection mode, USB 2.0, can I simply step down the 12v from the always-on 12v rail from the car to 5v, and essentially supply a constant 5V connection to the dock while only providing a data connection while the carputer is turned on?