how to communicate with iPod via their expansion connector ?

iPod communication?

Hi,
I wonder if anyone has any info about how to communicate with iPod via their expansion connector.

I see that there are USB, FireWire and Serial ports on that connector, and I would like to know what is the best way of making a simple device to communicate with it when it is docked on a home-made docking station.

I went over the document on this page: Apple Accessory Protocol - nuxx.net but I have some minor issues to deal with such as the state of the following signals:

PIN 18 3.3V 3.3V Power (+) Stepped up to provide +5 VDC to USB on iPod Camera Connector.
If iPod is put to sleep while Camera Connector is present, +5 VDC at this pin slowly drains back to 0 VDC.

PIN 19,20 +12V Firewire Power 12 VDC (+)

PIN 21 Accessory Indicator/Serial enable Different resistances indicate accessory type:

• 1KOhm - iPod docking station, beeps when connected
• 10KOhm - Takes some iPods into photo import mode
• 68kOhm - makes iPhone 3g send audio through line-out without any messages
• 500KOhm - related to serial communication / used to enable serial communications Used in Dension Ice Link Plus car interface
• 1MOhm - Belkin auto adaptor, iPod shuts down automatically when power disconnected Connecting pin 21 to ground with a 1MOhm resistor does stop the ipod when power (i.e. Firewire-12V) is cut. Looks to be that when this pin is grounded it closes a switch so that on loss of power the Ipod shuts off. Dock has the same Resistor.

Click to expand...

Thanks in advance,
/Farhad