Ipod serial remote system problem (4g, 5g, nano 3g)

Joined: 01 Jun 2008

Hi all,

First of all a huge thanks to everyone involved in these forums they've been an immense help to me with all the IPod interfacing aspects of my project.

I am sending simple remote mode serial commands to an ipod 5g and an ipod nano 3g, and neither have responded to any command yet.

here's my setup:
I have a C program (with pic programming) downloaded onto a PIC processor (using just the internal oscillator). The PIC uses a UART to send serial commands to the Rx pin on an ipod dock connector (from Ridax) hooked up to a 5g ipod. The pic operates at 3.3v from an external source (not from the ipod), 19200 baud rate, with ~15ms between each serial command sent. I am sending some control command followed by a button release command each time. The commands are copied and pasted out of all the accessory protocol command tables i've found throughout this site so they should be correct. I've verified with a logic analyzer that the correct serial commands are coming from the pic, with the timing i described.

heres a picture of my dock connector pinout:
http://uweb.ucsb.edu/~scottross/images/dockPinout.bmp

I've read that the ipod is fussy about the timing between commands, etc. Do i need an external oscillator? Also i've taken a signal reading directly at Rx pin 13 and it seems to be around 1.6v instead of the 3.3v i expected, coming from my PIC the serial signal is definently 3.3v in amplitude... is this normal?

I've really tried every configuration of the pins i could find on this site and other project sites, i've spent hours scouring this forum for things i could be doing wrong and haven't been able to make any progress. The only thing i could think of is its some timing issue with my commands, or that amplitude abnormality i described in the last paragraph. The only thing i've noticed about an ipod when its plugged in and being sent these commands is the playback timer on the ipod screen gets a little irregular (and actually stays that way forever :X but the audio doesn't skip or anything because of this)

Does anyone have some insight or help they could offer? This has been really frustrating..
Thanks in advance!