PDA, Tablet PC, MP3 players and other portable devices  > Apple pinouts
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

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

9 S-Video Chrominance output

for iPod Color, Photo only

or Component Video Y

10 S-Video Luminance output

for iPod Color, Photo only

or Component Video Pr

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

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.
19,20 +12V Firewire Power 12 VDC (+) 11,12
21 Accessory Indicator/Serial enable

Different resistances indicate accessory type:
1kOhm - iPod docking station, beeps when connected
10kOhm - 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.
68kOhm - makes iPhone 3g send audio through line-out without any messages
500kOhm - related to serial communication / used to enable serial communications Used in Dension Ice Link Plus car interface
  1MOhm - Belkin auto adaptor, iPod shuts down automatically when power disconnected Connecting pin 21 to ground with a 1MOhm 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.

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 manner. 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 10kOhm resistor, and 27 must be connected to the Ground (for example: pin 1) with a 10kOhm resistor.

iPod 5G can also be forced to charge by attaching the data + and the data - pins to the 5v via a 10k Ohm resistor ( BOTH PINS) and connecting pin 16 to the 5v (ground). (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), usb data- (25) should be at 2.8v, usb data+(27) should be at 2.0v. This can be done with a few simple resistors: 33k to +5v (23) and 22k to gnd(16) to obtain 2v and 33k to +5v and 47k to gnd to obtain 2.8v. This is a notification to the iphone that it is connected to the external charger and may drain amps from the usb.

To charge iPod Nano pins 25 and 27 should be tied together and then connected to a 10K ohm resistor, and the other side of this resistors then needs to be connected to 5v power.

It's also possible to charge the iPod's or iPhone's battery to make use the of internal +3.3v output (18) terminal to connect the USB Data + (27) thru a 47k ohms resistor and the USB Data- (25) thru a 47k resistor to the USB Power source +5v (23).  This way the USB function is still useable for normal operations and makes it easier the fit in a plug. The resistors are not to critical 2x 150k's still work.

Added correction: iPod 2.1A charger advertises 2.8V on D+ and 2.0V on D-.  Tying either wire to 5V could damage the target - use resistors tied to 5.1V and ground to be safe.

28 TPB (+) FireWire Data TPB (+) 3
29,30 GND FireWire Ground (-) 1,2

*There are two pins numbering schemes for this connector, this one (on right column) is from Apple manual. 
It is become available after publishing of most pinouts and 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

Pins 1, 2 connected on motherboard.
Pins 15, 16 connected on motherboard.
Pins 19, 20 connected on motherboard.
Pins 29, 30 connected on motherboard.

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. So, don't look at the numbers on the connector.

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

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.  

30 pin Apple iPod proprietary dock of Apple iPod, iPhone (2g, 3g), iPad Dock connector connector layout
30 pin Apple iPod proprietary dock connector
at the docking station
Source(s) of this and additional information: Andreas Brendle, ipodlinux.org and other sources, Apple.Com, http://www.head-fi.org/forums/f15/ipod-touch-line-out-question-446731/, www.wikipedia.com
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