technical diversions

a place to document my current project of connecting an iPod to a Saab 9-3 convertible with the factory audio system.

Wednesday, January 19, 2005

second best solution...

Still searching how to detect when the iPod is playing, so the radio can switch to the iPod input.

It looks, after spending "quality time" with the oscilloscope, that there is no easy way to detect on the dock connector when the iPod is active (playing)

I can detect, pin 18 3.3V, when the iPod is docked but the signal is present even if the iPod is off (sleeping). The only bad thing about this is that i will not be able to just recharge the iPod and i.e. listen to the radio/CD. As soon as i put the iPod the radio will switch.

The other problem is that no available cable carries pin 18, i was hoping to use a cable obtained from an adapter like the belkin to avoid dealing with the dock connector.

I will research today if i can use pin 21, accessory indicator to detect the presence of the iPod. Technically it should be possible because the iPod can read the resistance value on that pin to ground to detect the type of docking unit, but it may be a very small signal... the good thig is that that pin is available in the belkin car cable.



  • At 26 August, 2005 08:50, Anonymous Anonymous said…

    I get a bit confused about the reference to pin 21 as the accessory detector when the iPod itself uses pin 20 for this. Does this mean the dock uses a different pin than the iPod main connector? or does the pin count consider the shell as a connection?

    Thank you.

  • At 21 August, 2006 14:38, Anonymous Kevin said…

    Why don't you just use a switch?
    Wire it to get a constant signal from somewhere else (I use a random 5V pinout from the back of my car stereo). This way, when you have the switch flipped to on, the head unit is in Input mode.
    I also found a much cheaper dock connector with the necessary connections already wired. It also comes in a USB version. Plus it's easy to take apart to rewire it if you want. (ezLink LineOut Cable)


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