Audio Jack 2.5 mm

Brad Midgley bmidgley at
Mon Apr 30 00:54:31 CEST 2007


Judging from the high-resolution picture on the wiki it looks like the
> phone has a very special 2.5mm connector with 4 separate electrical
> connections (instead of the more common 3-connection version).  If I'm
> interpreting this correctly they are running both ground,
> left-earphone, right-earphone and microphone in one plug.  To me, this
> seems much more convenient than the 2x 3.5mm plug method used for
> computer headphones.

hopefully it is a 4-conductor connector. unfortunately there are two ways
manufacturers commonly wire up the 4-conductor 2.5mm connector. I have a set
that is wired for the palm way of doing it that I plan to try.

Nokia ships 4-conductor 3.5mm stereo headphones w/mic with their n800. The
jack is backward-compatible with 3-conductor headphones. It's the first time
I've seen a 3.5mm plug that could work with a microphone. It just might take
a while to catch on.

On the a2dp front, we got some help from Nokia on our codec and now it's
running nicely in (mostly) 32-bit ops. It should be pretty easy for the cpu
to encode stereo audio on the fly, but there is still a delay that we need
to accommodate.

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