- A2DP - audio
- AVRCP - remote control
- HSP, HFP - telephony
- CTP - cordless telephony (why not?)
That's the easy bit.
- Built in mic
- and voice-dialler.
- and noise-cancelling mics AND playback
- and volume-boost for quiet sources (I'm looking at you, DVD player)
- and AVC/compressor for classical music on noisy trains, planes and auto-mobiles.
That's easy too.
- I want it to take a micro-SD card for a built-in mp3 player
- And even have built-in storage, MTP or FAT32 block device.
- And have a built-in FM/DAB+ radio.
- It must charge from micro-USB, and be a USB audio-interface when plugged via USB.
- I also want a 3.5mm stereo line-in socket so I can use them as normal headphones. But I want it to take a 4-connector 3.5mm jack so that it can function as headphones with mic.
- It should detect when a 3-connector 3.5mm jack is inserted, and offer a 3.5mm microphone out socket.
- I also want a 3.5mm line-out that feeds whatever audio source is selected, so that I can feed into an amplifier or to a friend who has the same headphones (so line-out should not necessarily cut off the built-in speakers).
Did I miss anything?
- It should be able to record to micro-sd or built-in storage. In stereo. From the stereo noise-cancelling microphones any of the other audio sources, including USB, and the phone.
- I should be able to play from any source to the phone. While recording the phone conversation.
- And waterproof for jogging in the rain. (Not for me, for joggers).
For well less than £100.
On a stick. From standard parts.
BT interface. USB interface. Cross-bar audio mixer. SD interface. GPIO controlled radios.