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Research
A large amount of work went into determining whether this idea was actually feasible. No one appears to have made any similar efforts in 476 final projects before, and though there is a similar idea in ECE 313, that course was designed around a standard CD player and controlled the player by shorting the buttons.
We initially found the iPod Dock Connector pin-out, which is available from pinouts.ru After that, we eventually found the Apple Accessory Protocol, which is detailed best on the iPod Linux wiki.
Important Pins on the iPod
| Pin | Use |
| 1 | Ground |
| 11 | Serial Ground |
| 12 | iPod RX; microcontroller transmits on this pin |
| 13 | iPod TX; microcontroller receives from this pin |
| 21 | iPod Accessory resistor: We use 500k |
It's important to note which pins are the receive and transmit pins. On the pinouts.ru page, pin 13 is “Serial RxD,” which means serial receive from the iPod's point of view. Mixing it up could confuse you unnecessarily for a few hours.
Once we had a pinout and what looked like usable, if unofficial, documentation of the protocol, we started looking at actual connectivity to the iPod. There were a few efforts done by other people to create their own docks, but these were not quite what we were looking for.
After a bit of searching, we managed to find a hobbyist's website that had the actual iPod connectors available for sale. Even better, they also had a custom PCB available for sale to break out all of the individual signals from each of the pins, which was very useful because the pins themselves are rather small.
A short while later, we ended up discovering a second source for our PCB, which cost about the same as the original source but came with the dock connector pre-soldered, which was very useful as it was probably going to be a better soldering job than we could hope to accomplish by ourselves. Additionally, unlike the other source, it would ship within the United States. Using First Class Mail, we received our component in about 2 days (shipped on Thursday from CO, received on Saturday).