iPod Accessory Connector
The Apple iPod has become synonymous with a new generation of upwardly mobile, music loving people. As the iPod was developed new features were added and by the 3rd generation the "dock connector" was provided for accessory connection. The unique feature of the dock connector is the protocols that it supports. Unlike most equipment, the iPod can be connected by USB, Firewire and standard RS232 as accessories require. The connector also gives provides audio in, audio out, video out (for the newer iPod generations) and the power input lines 3.3V, 5V and 12V.
Having said all that, I have to admit that I personal do not have an iPod, so why my interest in the connector? Well, the number of accessories available for the iPod has grown exponentially since the addition of the dock connector. Some of these accessories are useless to someone that does not own an iPod, but some are and to be able to use them, information about the connector is required. (For an example see my Kenwood to computer interface)
Luckily for me, the work in understanding the dock connector has been done by many others. The best documentation I have found is provided at Ipodlinux. Readers should visit the site for full details but in aide of the people looking at my projects or doing their own, some of the more important information is covered here.
The connector is made by JAE as
part of their 30pin DD1 series. There is four products available: two
cradle connectors (one at right angles the other with a 75° tilt),
one direct plug and one receptacle. It is the receptacle that is built
into the iPod, the accessories using the cradles or the plug (depending
on the construction of the device). As with most companies, Apple has
bought a proprietary version which means sourcing the correct version
is a little more difficult. Luckily Ridax from Ipodlinux has
managed to get hold of the correct connector in bulk and now sells it
and covers at Ridax
iPod Dock Connector sales site.
The pin-out of the connector is as follows: (Items with notes are indicated and connections important for the Kenwood to Computer Interface are in red)
01 Ground (1)
02 Line Out - Ground (1)
03 Line Out - R
04 Line Out - L
05 Line In - R
06 Line In - L
07
08 Video Out (Composite Video)
09 S-Video Chrominance
10 S-Video Luminance
11 Serial GND
12 Serial TxD
13 Serial RxD
14
15 Ground (2)
16 USB GND (2)
17
18 3.3V Power
19 Firewire Power 12V (3)
20 Firewire Power 12V (3)
21 Accessory Indicator (4)
22 Firewire Data TPA-
23 USB Power 5V
24 Firewire Data TPA+
25 USB Data (-)
26 Firewire Data TPB-
27 USB Data (+)
28 Firewire Data TPA+
29 Firewire Ground (5)
30 Firewire Ground (5)
- Pins 1 & 2 connected together in iPod
- Pins 15 & 16 connected together in iPod
- Pins 19 & 20 connected together in iPod
- Pin 21 is used by the iPod to determine the accessory being used. 500k is used for serial communication. (See Ipodlinux for more)
- Pins 29 & 30 are connected together in iPod
That's about all that can be said about the connector. At the same time as introducing the dock connector, a serial connector built around the headphone socket was also introduced. The RxD and TxD lines are connected in parallel to the lines from the Dock connector. Ipodlinux has information on this if you need it. Once you have got your connection sorted you need to know what protocol to communicate in. USB and firewire are obvious, but the serial connection is explained here.