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Wednesday, September 4, 2013

Smartphone audio cable adapter


Unfortunately doesn't seems in the smartphone and tablet world, to exist a single standard for the audio connectors (see article about the smartphone audio jack).

On the market do exists cable converter of any kind, however they are often unnecessarily costly.
If you need an audio jack adapter between the main two standard in the smartphone world, OMTP and CTIA, here what I did.

Shopping list


Quite easy ... we need three things :
  • a 4 wire cable
  • a TRRS male jack
  • a TRRS female jack
I solved buying the needed material from Sparkfun.
I ordered a TRRS male jack with 18" of cable (CAB-11580) for $1.95 and a TRRS jack breakout (BOB-11570) for $3.95.
The TRRS jack breakout

It is possible maybe to find just a TRRS female for less, but the breakout is more flexible since it can be used also to provide a test platform (hook up oscilloscope, ecc.).
For about 9$ (the material plus shipment) is possible to have all the necessary to build the adapter.
A ready made cable converter can be found usually around 11$ plus shipment, but  the advantage to build it is that can be modified for other type of connections.

Schematic

OMAP<--->CTIA


Well, is really quite straightforward.
It is simply matter to connect the Tip and first Ring directly, and then swap  the other two.
The TRRS jack with the cable has this pinout :

  • Tip - red wire
  • Ring - white wire
  • Ring - green wire
  • Sleeve - black wire
On the PCB are marked the positions, so it is straightforward to connect the wires.
 




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