Hey guys,

It doesn't look like the ESP32 is going to work out. It does most of what I need it to, but on the calling side of things I can't get the software echo cancellation to work, and even then it's reported to be pretty poor. That means I would have to source and use a DSP to perform the software echo cancellation, and all the ones that would work are A: Expensive ($6+/unit at scale), B: impossible to buy in smaller quantities, and C: Not in stock for the next span of time.

I'm leaning towards the BM83 from Microchip, as it's still way cheaper than the BC127 I used before, and it has all the same bells and whistles (including a built-in DSP with acoustic echo cancellation).

That leads me to my current conundrum: microSD Card support. The BM83 does nothing to support it, so my wife actually suggested that I make an add-on module with an ESP32 and microSD card slot that will sit next to the BlueBus and stream your music files to the BlueBus. This means that I could bring microSD support to _all_ BlueBus units and I would also allow you to go through the directories using the HU so you can select your music files.

For those of you that want microSD card support, is this acceptable? The alternative would be a Rube Goldberg-esq setup where the BlueBus has an ESP32 and a BM83 but the ESP32 is only used for microSD support. This would increase the cost and complexity of the BlueBus, but you'd get negligibly better audio quality since the files wouldn't be transmitted over Bluetooth. Of course, it would only work for 2.x+ boards.

If you're wondering why I don't use an MP3 decoder, it's because they're $6.50/unit @ 250 units minimum -- no thanks.

Thanks!
-Ted