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This is my first post here so bear with me. Here is what I'm trying to do:

I am making an audio box that receives a Bluetooth audio signal from a mobile device and can rewind or fast forward that audio track you are playing through the box. This is the same concept as having Bluetooth headphones that let you play/pause/fast-forward/rewind. I have searched high and low on the internet to learn how a Bluetooth audio remote works and I have come up with nothing. I researched AVRCP and I think that is what I need to use to accomplish this but I don't know how to implement it and take an electrical signal from a switch and turn it into an AVRCP signal to rewind the song on my phone. Let alone how an AVCRP signal works and how it can specify volume up or down or play or pause.

I hope I explained this well enough. If not I can explain more. Thanks for listening an I hope someone can help me solve this or at least tell me if it's possible or not and then point me down an alternate path.

Jeff

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  • \$\begingroup\$ Do you have a particular Bluetooth device selected? That might be a good start. \$\endgroup\$ – uint128_t Mar 1 '16 at 1:06
  • \$\begingroup\$ I have a samsung galaxy 5 active. I bought a universal bluetooth transmitter and receiver to receive the audio from the phone and to transmit the signal back to the phone to control the rewind/fast-forward. \$\endgroup\$ – Jeff Mar 1 '16 at 15:53
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Most bluetooth modules that have audio controls have two options. One is basic gpio for button input. The other is serial rx/TX or some other protocol (spi/i2c/apple ipod communication/etc) for digital communication. The rest is handled by the firmware of the IC.

Look up the protocol for your specific bluetooth IC and follow that, or look for a module that has button inputs available.

There are a few example projects online of someone taking a generic bluetooth audio receiver, and hacking in a microcontroller or buttons to control the source. One did it with a factory radio, jeep or toyota. It's not hard once you know the protocol needed.

Here is one using a 2 dollar bluetooth audio receiver, and a MSP430 connected to the UART on the bluetooth IC. They use a remote control IR receiver, but the same can be done with buttons instead.

The AVRCP protocol on the phone side is essentially just a bluetooth keyboard. That's it.

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  • \$\begingroup\$ Here are the bluetooth protocols for the phone. Advanced Audio Distribution Profile (A2DP), Audio/Video Control Transport Protocol (AVCTP), Audio/Video Distribution Transport Protocol (AVDTP), Audio/Video Remote Control Profile (AVRCP), Audio/Video Remote Control Profile (AVRCP), \$\endgroup\$ – Jeff Mar 1 '16 at 15:57
  • \$\begingroup\$ @jeff updated with an example project. \$\endgroup\$ – Passerby Mar 6 '16 at 2:49

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