Gavin,
I'm bulding a paramotor headset.
My phone will connect to FSC-BT1058 for Calls and Music.
The BT modue is connected to a TI Codec via I2S (downlink and uplink).
Speakers (IEM) and mics are connected to the Codec.
For now (during development) I can work with two different FW versions, one supporting I2S input and one supporting Absolute Volume. However, I really need a combined version in a month or so.
I can share more details over email if needed.