Reacting to multi-buttons wired headphones

Question

I am driving some experiments with a pair of a-JAYS Four headphones (having 3 buttons on its wired remote/mic) plugged onto a Galaxy Nexus (ICS 4.0.2).

My issue is that only the middle button is 'recognised' by a test app I have written, i.e. triggering both Intent.ACTION_MEDIA_BUTTON and/or Activity.onKeyDown callback with KeyCode 79 when it is pressed.

Pressing the two other buttons don't trigger any of the previous methods. For info, those headphones and its 3 buttons work on Apple iPhones and Apple computers (at least a MacBookPro 2011), as advertised on the box...

Firstly I thought Android or my device could simply not handle more than one button on a wired jack remote (even if that sounds weird...) but then I had a try with a pair of headphones from HTC (the ones coming with one of their Desire device) having 3 buttons. Middle button would react the same way as my a-JAYS, but the two other buttons are also recognised with KeyCodes 87 and 88, respectively Play Previous and Play Next media keys.

So it seems that either the device or the low levels layers of Android are simply not able to catch certain headphones buttons signals :/ (at least those which are not 87 and 88)

Any idea anyone about how to make Android able to recognise other buttons/signals from such headphones as Apple compatible ones? Would it imply low levels drivers writing for ICS or am I missing something really obvious?

Any help would be much appreciated. Can post my test-app code if needed.

Cheers

Answer 1

The signals/ resistance from the volume control buttons (1.525-1.495 V for volume down, and 1.619-1.587 V for volume up) are currently unable to be recognized through the android framework's software. I believe this has to do with Apple having a patent on the designated volume controls and so Google won't release to developers how the framework recognizes particular signals through the fourth connector on the headphone jack. The center/mic/action buttons on headsets generally work, it shorts the path from ~2V to ~0V and Apple does not own the patent for that. If someone could figure out how to interact with the inputs on their own that would be huge. I am tempted to learn app development and find a workaround.

Answer 2

The problem is more complicated that it seems: http://david.carne.ca/shuffle_hax/shuffle_remote.html .

Answer 3

I have to emphasize that I am no expert on this topic, but from what I have read and tried so far I conclude that it is not impossible to have an Android phone respond to an iPhone headphone's volume buttons, but for some reason the performance is poor/lagging.

There are some apps trying to do the magic, but they are too unreliable for everyday use. I suppose the problem is that triggering the signal may have to be implemented at a lower OS level than most regular apps have access too.

The solution could probably be some kind of a ROM mod...

If you can implement this, I am sure it would be a big deal for the Android community, and maybe a good biz for you.

Kind Regards, your fellow Hungarian Gergő

Answer 4

You have to press and hold the middle button while plugging the headphones to the jack. That will make the microphone work on an Android. It works on my HTC Thunderbolt.

Answer 5

I believe it's a hardware issue (at least in regards to Apple headphones). If you look at the plug on those they have four contacts instead of the normal three. I'm willing to bet they run their button signals through that extra contact. AFAIK, there is no Android equipment wth jacks to match that.

So, ultimately I don't believe you can make apple earphones with buttons work for android (as far as button functions go).

Answer 6

You have to hold the middle the whole time for it to work. If you let go and not playin music it says accsessary not supported but if u play music and let go it simply stops the music until you hold it again. Maybe tape the middle button shut really tight?

Answer 7

If you look at the four contacts, tip-ring-ring-sleeve (TRRS), and know that MOST headphone sets are:

• tip: left
• ring 1: right
• ring 2: ground
• sleeve: mic

(1/4 inch pro audio stereo plugs are known as TRS - tip-ring-sleeve)

although some reverse the ground and mic contacts, what you need to know as far as how the device recognizes the different buttons you have, is that those buttons are making a short between the ground and mic contacts. (before IR, old school WIRED remotes for VCRs used resistance for different functions)

Now your homework to find out what is going on is:

1. measure the resistance between ring 2 and the sleeve for each one of your buttons
2. find out if it is a momentary short, or constant
3. if you have some other headphone/mic device that works correctly, measure those impedance (resistance) too

I don't know how into this you want to get, but you can buy resistors with the correct impedance to get the functions you want out of the Android device, the question is, do you know what functions the device is capable of, and what those impedances are that trigger that function.

daniel@destinypatrolsoftware.com