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General => General Chat => Topic started by: linux-works on June 27, 2015, 08:52:42 pm

Title: CTIA inline remote control protocol(s) and vendor-specific extension?
Post by: linux-works on June 27, 2015, 08:52:42 pm
anyone here familiar or experienced in this stuff?

I'm talking about the TRRS small size headphone jack that has a 4th band for remote control.  I've read here:

http://www.wisebread.com/build-a-cable-to-control-your-android-phone-while-you-drive (http://www.wisebread.com/build-a-cable-to-control-your-android-phone-while-you-drive)

and other places that its resistance based for some functions and 0 ohms to gnd for play/pause.  I have an android earbud cable that has this function and also a base noise cancelling cable that does this, as well.

here's where I'm a little confused; I tried using this cable on a player I recently bought (Fiio x3-II) and that claims to have ctia remote ability.  ok, fine, go to its config menu (on the audio player), enable the remote control option and lets see what happens.  I plug the cable with the 4 bands into the phones-out jack and press buttons.  the pause/play button does actually toggle those modes, so that's great.  but skip back and forward don't do anything.

then, just while trying random stuff, I multiclicked on the pause button.  that changed songs!  lets try some variations, 2 clicks and 3 clicks.  yup, that skips one way and the other way.  that's the 4 functions, but they are overloaded on the play/pause 0ohm-to-gnd band (or button) and the restance-based style does not seem to be supported by this player.

has anyone seen this before or know if this is just a vendor-strangeness thing?  I just happened to figure this out by trying multiclicking and I'm not even sure what made me do that ;)  I can now create some small controller that will receive my command and translate to multi-tap stuff, but it just seems strange that they'd do it this way on the player and become incompatible with, what seems to be a standard that uses R values and not pulses on a single band.

I have not tried to contact the vendor yet, but curious if anyone has seen this or tried to work with this inline remote stuff before.