Idiot's Guide To Bluetooth Design

Discussion in 'Technical Corner' started by weirdjim, Feb 26, 2019.

  1. weirdjim

    weirdjim En-Route

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    I admit to being stone-bone ignorant regarding Bluetooth design. I do know I'm in the throes of a new audio panel design and I'd really like to include the capability of working with aircraft bluetooth headsets if it isn't prohibitively expensive.

    Anybody got a lead to "The Compleat Idiot's Guide To Bluetooth Design"?

    Thanks,

    Jim
     
  2. Raymo

    Raymo Pre-takeoff checklist

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  3. weirdjim

    weirdjim En-Route

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    Github talks about how to select a product for bluetooth, and Digikey also has product, but I'm looking for a discussion of how it works, what peripherals are used for what. it seems real simple to transmit 4 channels of bidirectional voice for a few feet, but the devil is in the details.
     
  4. Cap'n Jack

    Cap'n Jack Final Approach

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    My experience has solely been the RFCOMM protocol (RS-232 over BlueTooth), but there are others for audio devices (Head set protocol, Hands Free, Audio, Audio/Video). I've also used libraries of code rather than "roll my own"
    List of BT protocols: https://en.wikipedia.org/wiki/List_of_Bluetooth_protocols
    Decent overview: https://developer.apple.com/library.../BT_Bluetooth_Basics/BT_Bluetooth_Basics.html

    Although you mentioned DigiKey, perhaps this has information useful: https://www.digikey.com/en/articles...balance-range-complexity-cost-and-performance
    Making your own BlueTooth seems on a par, to me, with making your own GPS receiver.
     
  5. rpadula

    rpadula En-Route

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    Jim,

    You want what is called Bluetooth classic. An aircraft headset likely uses HFP (hands free profile) for the mic and earpieces, and there's also A2DP for stereo music streaming. Here's a basic presentation on Bluetooth audio from Silicon Labs, one of the big BT silicon vendors:

    https://www.silabs.com/documents/login/presentations/Developing-Bluetooth-Audio.pdf

    There's really little need to "roll your own." The major players sell pre-made, FCC certified Bluetooth modules that you could solder in to your PCB. Many of these have audio in and out connections as well. And they seem to cost about $20 or less.

    SiLabs modules here: https://www.silabs.com/products/wireless/bluetooth/bluetooth-classic-modules

    My contact there recommended the WT32i:
    https://www.silabs.com/products/wir...-classic-modules/wt32i-bluetooth-audio-module
    https://www.silabs.com/documents/login/presentations/WT32i-Bluetooth-Audio-Module-Presentation.pdf
    https://www.silabs.com/documents/login/reference-designs/Reference-Design-DKWT32i.pdf
    https://www.silabs.com/documents/login/data-sheets/WT32i-DataSheet.pdf
    https://www.silabs.com/documents/login/user-guides/UG215.pdf

    Microchip also makes silicon and modules:
    https://www.microchip.com/design-centers/wireless-connectivity/bluetooth/applications/audio
    https://www.microchip.com/ParamChartSearch/Chart.aspx?branchID=12094

    One of my buddies bought some BT module on Ebay for the tube amp he was making. He said it had some software to set it up (i.e. so it shows as "Mark's Tube Amp" in the Bluetooth connections list, etc) and streams music straight from his iPhone to the amp. I'll see if I can find out which one it was.
     
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  6. weirdjim

    weirdjim En-Route

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    Sorry I'm so late, guys, but thanks a million for all your input.

    Jim
     
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  7. Doug Reid

    Doug Reid Pre-Flight

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    I use a bluetooth module to transmit ForeFlight audio to my intercom. The module will also connect to my phone. The biggest complaint I have is latency. Bluetooth range is very short...about 10 feet on most units.The module I use has its own lithium ion rechargeable battery...I paid $3 on ebay.
     
  8. Chip Sylverne

    Chip Sylverne En-Route PoA Supporter

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    Fear is the poison of our lives.
    When not synced to video, how does the audio latency manifest itself as a problem? It's just milliseconds, right? I just ordered a $10 Ebay receiver/transmitter that has bluetooth 5.0 to play with a headset design. 5.0 is supposed to minimize latency.
     
  9. Doug Reid

    Doug Reid Pre-Flight

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    It comes into play when you use it to make phone calls...to stream audio, you do not notice the delay. Bluetooth 5.0 is probably better.
     
  10. Sinistar

    Sinistar Pattern Altitude

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    Would you please clarify...do you mean headsets like Bose and Lightspeed that have bluetooth capability? If so they usually get the bluetooth from the phone/tablet right?

    Are there other aviation headsets that are wireless?...besides the Tango's (which use a non bluetooth frequency)

    Or maybe you mean something else?