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Wednesday, February 16, 2011

iPhone USB Charger to make or trouble-shoot

First, you need 4 resistors with these values: 2 of 33 kΩ, 1 of 47 kΩ and 1 of 22 kΩ.

Apple iPhone (1G, 3G, 3GS, 4) Dock connector



30 pin iPOD proprietary connector layout


Pin Signal Description
1 GND Ground (-), internally connected with Pin 2 on iPhone motherboard
2 GND Audio & Video ground (-), internally connected with Pin 1 on iPod

3 Right Line Out - R (+) (Audio output, right channel) . See also

Apple iPhone headset  connector pinout
4 Left Line Out - L(+) (Audio output, left channel)
5 Right In Line In - R (+)
6 Left In Line In - L (+)



11 GND If connected to GND the iPhone sends audio signals through pin 3-4,

otherwise it uses onboard speaker.
12 Tx iPhone sending line, Serial TxD
13 Rx iPhone receiving line, Serial RxD
14 RSVD Reserved
15 GND Ground (-), internally connected with pin 16 on iPhone motherboard
16 GND USB GND (-), internally
connected with pin 15 on iPhone motherboard
17 RSVD Reserved
18 3.3V 3.3V Power (+) ?
19,20 +12V Firewire Power 12 VDC (+)
21 Accessory Indicator/Serial enable Different resistances indicate accessory type:

  1kOhm - docking station, beeps when connected

   68kOhm - makes iPhone 3g send audio through line-out without any


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

pin is grounded it closes a switch so that on loss of power the Ipod

off. Dock has the same Resistor.
22 TPA (-) FireWire Data TPA (-)
23 5 VDC (+) USB Power 5 VDC (+)
24 TPA (+) FireWire Data TPA (+)
25 Data (-) USB Data (-)
26 TPB (-) FireWire Data TPB (-)
27 Data (+) USB Data (+)

Pins 25 and 27 may be used in different manner.

To charge an

iPhone 3G / iPod Touch 2nd gen or Ipod Classic (6th Gen)

data- (25) should be at 2.8v, usb data+(27) should be at 2.0v. This can

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.

It's also possible to charge the iPod's or iPhone's battery to make

the of internal +3.3v output (18) terminal to connect the USB Data +

thru a 47k ohms resistor and the USB Data- (25) thru a 47k resistor to

USB Power source +5v (23).  This way the USB function is still useable

normal operations and makes it easier the fit in a plug. The resistors

not to critical 2x 150k's still work.

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

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 iPhone dock connector cable

and look at the connector itself, on the back side, where it is soldered,

can see the number 1 and 30 (e.g. pin 1 and 30). In this description

is INVERSED: pin 1 is pin 30 and pin 29 is pin 2, so, don't look at numbers


This device may be connected to the firewire computer port by straight

cable (TPB+/-, TPA +/- should be twisted pairs in cable). It seems there are

no file transfer allowed, but it can charge via this interface.


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