motorola usb->3.5->headset: compatibility?

Joachim Steiger roh at
Sun Jun 29 18:28:41 CEST 2008

arne anka wrote:
> hi,
> the other day i saw from motorola an adaptor changing a mini-usb into a  
> 3.5(?)mm headset jack.
> does anybody know whether it works with motorola phones only?
afaik yes.
means it only works with motorola devices.
motorola has 8-13 different 'functions' on the 5pin mini-usb-b
connector, including mono headset, stereo headphones out, high and low
voltage programming mode, usb-masstorage, usb-acm, serial debugport and
some others.

but thats only possible since they build them in such massive volumes
that the high initial cost for the custom-asic which contains
pmu+codec+usb-py+serial+mux makes any sense at all.
besides that, i would like to charge or speak ip to my phone while its
playing music, so i do not really favor too much muxing anywhere.

4-ring 3.5mm jack + usb for charging as well as data gives one the
biggest number of reasonable use-case combinations while still keeping
it simple.
after all we do not want bags full of adapters anymore, just because
everybody uses a different plug for the same thing.

> if not, it easily could solve the issues with audio jack of the freerunner  
> (whose impact i still fail to understand).
sadly not. see above.



Joachim Steiger
Openmoko Central Services

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