> when starting io-fs-media with option -dipod,transport=ser:dev=/dev/ser1 do I 
> have to specify the acp=i2c option also, or is it only needed when starting io
> -fs-media -dipod with transport option set to "usb"?

Well, specifying the acp=i2c option tells the iPod driver if you have an authentication coprocessor or not. If you do 
have an auth chip you should use that option regardless of the transport being used (serial or USB).

If you don't have an authentication coprocessor, you can still get playback with analog audio over a serial connection, 
so the authentication is really only mandatory for USB playback.

Regards,
Gilles