Apple iPod, iPhone (2g, 3g), iPad Dock connector pins and signals

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Used in 3rd and later generation iPods for charging, connecting to a PC via USB or Firewire, to a stereo via line-out, to a serial device (controlled via the Apple Accessory Protocol). This connector exists in most Apple iPod MP3 players (iPod 3G, 4G, 5G Video, 5.5G Video, Nano (1G, 2G, 3G, 4G), Mini, Classic, Touch, Touch 2G, and iPhone (1G, 3G, 3GS, 4 and 4S))

Pin	Signal	Description	Apple pin numbering*
1	GND	Ground (-), internally connected with Pin 2 on iPod motherboard	30
2	GND	Audio & Video ground (-), internally connected with Pin 1 on iPod motherboard	29
3	Right	Line Out - R (+) (Audio output, right channel)	28
4	Left	Line Out - L(+) (Audio output, left channel)	27
5	Right In	Line In - R (+)	26
6	Left In	Line In - L (+)	25
7	?		24
8	Video Out	Composite video output (only when slideshow active on iPod Photo) or Component Video Pb	23
9	S-Video Chrominance output	for iPod Color, Photo only or Component Video Y	22
10	S-Video Luminance output	for iPod Color, Photo only or Component Video Pr	21
11	AUDIO_SW	If connected to GND the iPhone sends audio signals through pin 3-4, otherwise it uses onboard speaker.	20
12	Tx	ipod sending line, Serial TxD	19
13	Rx	ipod receiving line, Serial RxD	18
14	RSVD	Reserved	17
15	GND	Ground (-), internally connected with pin 16 on iPod motherboard	16
16	GND	USB GND (-), internally connected with pin 15 on iPod motherboard	15
17	RSVD	Reserved	14
18	3.3V	3.3V Power (+) Stepped up to provide +5 VDC to USB on iPod Camera Connector. If iPod is put to sleep while Camera Connector is present, +5 VDC at this pin slowly drains back to 0 VDC.	13
19,20	+12V	Firewire Power 12 VDC (+)	11,12
21	Accessory Indicator/Serial enable	Different resistances indicate accessory type: 1 kΩ - iPod docking station, beeps when connected 10 kΩ - Takes some iPods into photo import mode 6.8 kΩ - Serial port mode. Pin 11-13 are TTL level. Requires MAX232 chip to convert to RS232 levels. 68 kΩ - makes iPhone 3g send audio through line-out without any messages 500 kΩ - related to serial communication / used to enable serial communications Used in Dension Ice Link Plus car interface 1 MΩ - Belkin auto adaptor, iPod shuts down automatically when power disconnected. Connecting pin 21 to ground with a 1 MΩ resistor does stop the ipod when power (i.e. Firewire-12V) is cut. Looks to be that when this pin is grounded it closes a switch so that on loss of power the Ipod shuts off. Dock has the same Resistor.	10
22	TPA (-)	FireWire Data TPA (-)	9
23	5 VDC (+)	USB Power 5 VDC (+)	8
24	TPA (+)	FireWire Data TPA (+)	7
25	Data (-)	USB Data (-)	6
26	TPB (-)	FireWire Data TPB (-)	5
27	Data (+)	USB Data (+) Pins 25 and 27 may be used in different manners: To force the iPod 5G to charge in any case, when USB Power 5 VDC (pin 23) is fed, #25 must be connected to 5V through a 10 kΩ resistor, and #27 must be connected to the Ground (for example: pin 1) with a 10 kΩ resistor. iPod 5G can also be forced to charge by tying both #25 and #27 together, then connecting both to 5V via 10 kΩ resistor, and connecting pin #16 (usb-gnd) to the 5V. (Confirmed working with iPod 5G 20GB). This provides 500mA of current for charging. For quicker charing, up to 1A, see below. To charge an iPhone, 3G, 3GS, 4 / iPod Touch, 2nd gen, 3rd, 4th or iPod Classic (6th Gen), pin #25 (USB D+) should be at 2.8V, pin #27 (USB D-) should be at 2.0V; this is the output of the iPod 2.1A charger. There is a notification on the iphone that it is connected to the external charger and may drain amps from the usb. This can be done in a few ways: 33k to +5v (#23) and 22k to usb-gnd (#16) to obtain 2V; 33k to +5v and 47k to gnd to obtain 2.8V. 47k to internal +3.3v (#18) for 2.0V, 47k to +5V (#23) for 2.8V. The resistors are not to critical: 2 150k ohm resistors still work.  This way the USB function is still useable for normal operations and makes it easier the fit in a plug. To charge iPod Nano pins 25 and 27 should be tied together, then connected to +5V WITH a 10 kΩ resistor. Tying either wire to straight to 5V could damage the target - use resistors tied to both 5V and ground to be safe.	4
28	TPB (+)	FireWire Data TPB (+)	3
29,30	GND	FireWire Ground (-)	1,2

*There are two pins numbering schemes for this connector. The one on right column)is from Apple manual. It only became available after publishing of most pinouts and is not used on this site.

Back side of dock connector;
 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

On the iPod motherboard, pins 1&2, 15&16, 19&20, and 29&30 are connected together.

If you disassemble the original apple-ipod-dock-connector-cable and look at the connector itself, on the back side, where it is soldered, you can see the number 1 and 30 (e.g. Pins 1 and 30). In this description the NUMBERING is INVERSED: Pin 1 is Pin 30 and Pin 29 is Pin 2.

Apple Accessory Protocol

The remote control, iTalk and other serial devices use the Apple Accessory Protocol for communication with the iPod. This protocol was introduced with the 3rd generation iPods, and is also compatible with the 4th generation iPods and mini iPods. The connections uses a standard 8N1 (one startbit. 8 data bits, one stop bit) serial protocol, 19200 baud (higher rates up to 57600 are also possible, but speeds faster than 38400 may cause problems with large amounts of data), with a delay of 12 microseconds inserted between the end of the stopbit and the beginning of the next startbit (also works without this delay).

• Electrical: high +3.3V, low 0V
• Default line state: high.

Codes used for communication with peripherals are here

Additional notes

• This device may be connected to the firewire computer port by straight cable (±TPB, ±TPA should be twisted pairs).
• The iPod Nano 4th Gen no longer charges from the 12 V supply on the Firewire pins. If you tie Pins 25 and 27 together and then connect a 10 kOhm resistor to ±5 volts to pins 23 and 15 (or 16), it will charge. If you don't tie Pins 25 and 27 together, it won't charge.
• The iPod Touch 3G: may also require for Pins 1 and 2 (GND and audio out GND) to be connected in order to output audio (Pin 11 to GND). Works with appr. 500 kOhm between pin 21 and GND.
• The iPod Touch 2G requires Pin 11 to be connected to Pins 15/16; then connect that to Pin 21 with a 68 kOhm resistor to use the audio line out. This is because the device needs to be told to redirect the signal to the Line Out pins rather than to the built-in speaker. This explains why certain accessories won't work with the iPod Touch 2G and maybe even the iPod Touch 3G. The iPod nano 5G will require the Pin 11 connection but not the 68 kOhm resistor for redirecting audio. Nano 5G: connecting the 68 kOhm resistor to ground will disable the audio redirection accomplished by connecting Pin 11 to ground.
• You may need to ensure that Pins 1 and 2 are connected to GND for proper charging to occur.