Saturday, July 4, 2009

Skype in iPod touch 2g: do-it-yourself microphone

Unlike iPhone, the iPod touch has no integrated microphone, second generation ipod touch, however, supports external microphone connected to the earphone plug, which allows the use of VoIP applications such as skype or fring with a wi-fi link. All you need is the right microphone; of course you can buy one for example from apple or griffin, but is funnier and cheaper to do it at home.

(By the way, if you'd like to download music for your ipod or iphone from youtube, check this post)

We will see how to buid a handsfree set that can be connected to an iPod touch 2g and used with skype or other application that uses the microphone; this will also work with an iPhone.

What will we need:
  • Handsfree set for mobile phone or other device with microphone and earphone. In this example we will use a popular one from nokia:

    Handsfree for skype in ipod touch

  • A 4-conductor 3.5mm plug, also known as TRRS plug:

  • Soldering iron

  • Multimeter
First let's identify microphone and earphone cables, for this we open the microphone case. This is a front view:

Nokia handsfree microphone

Seen from the back, at the right there are the lines coming from the earphone (green) and we can trace them back, the other two are microphone's (pink). Now we identify the color of the cables that correspond each one, polarity doesn't matter, only which pair of colors matching each:

iPod touch skype microphone and earphone lines

Colors will vary depending on the handsfree model, in this case they are:
  • Earphone: green and red-green

  • Microphone: yellow and red
ANow let's cut the cable of the handsfree and near the orignal connector and split the cables:

And solder them to the TRRS connector, like this:

You can note that one of the contacts is not used, since it is for the other channel in a stereo signal and the handsfree is monophonic. As VoIP apps like skype are not stereo, this is not a problem.

Some cables have a thin layer of insulating varnish that will complicate the soldering process, in this case gently scratch the insulation with a sharp edge, to remove the insulating varnish before soldering.

It is also wise to verify with the multimeter that there are not short-circuits in the solders, you should be able to measure the resistance of the microphone and earphone (some hundred ohms typically) and between them there should be an open circuit.

Finally, a video of the working handsfree:

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