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I just see the post that make your own Google Glass earphone. on How can I get audio output from Google Glass to a 3.5mm headphone jack?

I'm curious that is there a document for Google Glass or Android in general document that defines that kind of function?

Thanks

Community
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Deqing
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2 Answers2

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It's undocumented, but its pinout has been experimentally determined. When a 500kΩ resistor is placed between pin 4 (Sense) and pin 5 (GND) of a micro-USB plug, the system treats it as an audio device. The pinout is:

  • Pin 1: +5V. This charges the battery. Glass can be charged while audio is active.
  • Pin 2: Right audio out
  • Pin 3: Left audio out
  • Pin 4: Sense. Connect to Pin 5 with a 500kΩ resistor.
  • Pin 5: GND
Zack Freedman
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  • I'm using V1.0 Glass and I haven't tried the earbud on my Glass. But I haven't found any USB switch in teardown photos nor any related code in kernel source released in April. May be the 2.0 one is different? – Deqing Nov 15 '13 at 22:17
  • I don't recall where, but I've heard some users state that the USB earbuds for 2.0 work for the first version. – JRomero Nov 16 '13 at 14:38
  • For my own reference. In tear down photo in catwig.com, there is a BGA12 chip with mark AAU below Audio codec TWL6041. MAX14532E matches the mark and location of capacitor and resistor matches the pinout. – Deqing Nov 18 '13 at 16:55
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Try to answer my own question with some research.

From the tear down images and kernel source code. I found something.

Google Glass uses a MAX14532E chip to switch 3 functions: USB, TTY, Audio, or nothing.

However the ID resistor checking routine only check 500K(Stereo) or 1M(Mono). If resistor of those two values are detected the micro usb will switch to Audio automatically. I still need to do more test to see if I can switch it manually.

BenMorel
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Deqing
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