QymBuds Air is happening!
Despite all the difficulties, the wireless TWS earphones QymBuds Air are happening! Yes, you read that right — True Wireless Stereo. It means there will be no wires at all: none to the playing device and none between the left and the right cup. The cups are completely independent of each other, each has its own battery and can play music on its own. Getting there was far from easy.
As it turns out, the world of controllers for BT audio is a very closed one. There are a few Chinese OEMs and Qualcomm, and that is that. Finding the microcontrollers themselves on the open market is impossible. The SDK/ADK (the tools for building firmware and software) are not publicly available, and neither are datasheets, application notes or examples. All you can find is this:
- Ready-made modules of dubious quality, on microcontrollers marked A3 from the OEM/ODM maker Bluetrum, which as far as I understand works only with Chinese companies. There is no way to work with such modules; they come as they are.
- Ready-made modules on Qualcomm chips. On AliExpress it is all rather murky: modules arrive with odd firmware, in one place the functionality is cut down, in another it is there but switched off. As for software, all that is freely available are old utilities that can pull a firmware backup off the chip, patch it for the functionality you want (though not all of it) and write it back. It is unclear how that old software works with the newer microcontrollers. But there is a ray of light: you can register as a developer on the site, though getting access to the documentation and the SDK/ADK requires passing a company check. Qualcomm microcontrollers are very capable and support a lot of formats and codecs, but the price bites.
You will ask what I am so pleased about then. And I will answer: I have a working TWS prototype of QymBuds Air. And that is not all.
In the course of the search I managed to reach a supplier of Airoha microcontrollers and to get at least some sort of datasheet and application note. Right now the first version of the board is being actively developed.
(The schematic of the main board)
(The 3D view and the PCB)
I have not given up on Qualcomm, and perhaps I will get access to the developer section. Then there will definitely be a Pro version of the wireless earphones. For now I can work with the Airoha microcontrollers, and there are plenty of plans. The current board can take audio both over Bluetooth and over a wire. The cups charge from an ordinary +5 V phone charger. The charging connectors are magnetic Pogo pins. Coming up next: long tests, picking the right battery capacity, putting wireless charging into each cup, developing a wireless charging case, and much more.
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