The next step is to work on the iPhone's connection. You should make yourself familiar with the connector. If you use a breakout board, this is quite easy. However, if you are using an iPhone cable, things are a little trickier. Firstly, you should look at Pinout.ru's iPod Guide
that lists the ports we need. We are aiming to use the iPhone's built in serial connection. The pins we need are:
- Pin 1 for GND
- Pin 13 for RX
- Pin 18 for 3.3V(+ve)
We could use pin 12 for TX as well but the ID-12 doesn't need data sent to it and I have had significant problems in sending data FROM the iPhone. If anyone knows why this is so, do let me know. Regardless, the iPhone only needs to receive and this is well because these two pins are very close together.
First, either solder your wires into the breakout board or open up the iPhone cable. To open a genuine iPhone cable, you need to run a thin blade around the inside of the plastic case. A small amount of force should release the clips on either side and then pulling on the metal plug with a pair of pliers should do the job. Be careful at this stage though as its VERY HANDY TO KEEP THE PLUG INTACT.
Taking apart the plug should reveal 4 cables. A genuine iPhone cable will have a sheath and small gold connectors. Cheaper cables will be glued in place and this can wreak the project. You dont want glue inside the unused sockets and the less force you need to remove the cables, the better.
Removing the small plugs requires a lot of force and yet, you MUST be as delicate as possible. The connectors are attached to the wires with a very small amount of solder. If the connectors snap they cannot be used and if the solder snaps, you will need to solder them again and if you use too much, the plugs will not fit back into their sockets. Also, you are limited on how many times you can place the plugs as the sockets will wear out. I personally went through 5 cables with this method; two of them were genuine. The geunine ones wear much less.
Place the black wire into the ground. You can decide which colour goes into which socket. I chose green for Pin12, white for Pin13 and Red for Pin18. Remember which is which!