First the pinout:
dock pinout for serial i/o

iPod's white side up

the cyan one are the serial line:

12 TxD ipod sending line

13 RxD ipod receiving line

Magenta pads enable the dock serial connector

the green one are audioground,r,l

red +12V charging
grey GND

the remote control is using 19200 baud 8N+1 (one startbit 8 data bits 1 Stopbit) i measured a delay of 12 microseconds between end of the stopbit and the beginning of the next startbit.But it is also working without this delay.

Electrical: high +3,3V low 0V

default line state: high