I believe I have found the proper resistance to mimic a dock. I have used 66kohm from pin 21 (ACC) to pin 1 (GND) and the "This accessory is not made to work with the iphone" message does not come up when connecting the iphone to the line-out circuit. I will post what I believe to be the schematic for the IPhone dock, which is how I determined what the proper resistance should be. I think the majority if this circuit is a debounce switch for the line-out jack. This is done by essentially floating pin11 (serial gnd) until the jack is inserted into the plug (J4). R21, R23, and R4 are connected serially between VDD and GND when no device is connected to the line-out plug. Most of the voltage drops across R21 which means Q2 is "low". Once the device is plugged in, R21, R23 and R4 are disconnected from GND so there is no voltage drop across these resistors which means Q2 goes high (~3.14v in reality). Since the "black box" is probably two transistors, I think that Q2 "on" allows Q1 and Q3 to connect (emitter to collector), effectively grounding pin 11 (serial gnd). At the same time, this sudden change in voltage is seen as a trigger (edge) to the HFC4098B. I believe this causes Q(2)' to either pulse Q5 or to stay at VDD but it allows Q4 and Q6 to connect. When Q4 and Q6 connect, R18 and R12 are now in parallel for an equivalent resistance of 67.013k. The resistor R18 is what everyone sees when probing the dock but I believe that when power is applied to the monostable multivibrator, the resistance becomes the equivalent parallel value. I used an exact 66k series combination since that's as close as I cared to get and it is working for me.
Sunday, January 4, 2009
IPhone Dock (Part II)
I believe I have found the proper resistance to mimic a dock. I have used 66kohm from pin 21 (ACC) to pin 1 (GND) and the "This accessory is not made to work with the iphone" message does not come up when connecting the iphone to the line-out circuit. I will post what I believe to be the schematic for the IPhone dock, which is how I determined what the proper resistance should be. I think the majority if this circuit is a debounce switch for the line-out jack. This is done by essentially floating pin11 (serial gnd) until the jack is inserted into the plug (J4). R21, R23, and R4 are connected serially between VDD and GND when no device is connected to the line-out plug. Most of the voltage drops across R21 which means Q2 is "low". Once the device is plugged in, R21, R23 and R4 are disconnected from GND so there is no voltage drop across these resistors which means Q2 goes high (~3.14v in reality). Since the "black box" is probably two transistors, I think that Q2 "on" allows Q1 and Q3 to connect (emitter to collector), effectively grounding pin 11 (serial gnd). At the same time, this sudden change in voltage is seen as a trigger (edge) to the HFC4098B. I believe this causes Q(2)' to either pulse Q5 or to stay at VDD but it allows Q4 and Q6 to connect. When Q4 and Q6 connect, R18 and R12 are now in parallel for an equivalent resistance of 67.013k. The resistor R18 is what everyone sees when probing the dock but I believe that when power is applied to the monostable multivibrator, the resistance becomes the equivalent parallel value. I used an exact 66k series combination since that's as close as I cared to get and it is working for me.
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2 comments:
i disassembled a apple usb cable to connect my iphone to my tv. I moved the pins to 2,3,4 & 8 and spliced an av cable in. sound still comes out of the speaker and it still doesnt recognize it. If i add a 66kohm resister from pin 21 (ACC) to pin 1 (GND) will it work?
hi
do you know how can i use the iphone 3gs main connactor line out for get audio also in phone call ?
thanks
amit
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