It's super helpful that you noticed those pieces of information before I ran into those same frustrations on my own. Thanks!

Regarding the audio input, I was hoping that the RN-52 inputs could be made into a stereo line-in, like the BC127. On the Purpletooth board, that part at least worked perfectly. there was a small switch on the board which switched it between mic input and line input. Stereo audio was great. I admit that I didn't look closely to be certain that this could be done with the RN-52 before I ordered it. I was hoping to dig up the docs on it after it arrived.

I'm crossing my fingers really hard about the RN-52 chip, because I think I've taken that BC127 chip about as far as I can go with it unless Sierra finds and fixes the incompatibilities. I've got all the special cases and problem workarounds coded in, and they work (I can hear the empeg through the car stereo, change tracks on it with the car stereo and steering wheel controls, play and pause, etc,), but there are still problems:

- It's only working in "old avrcp" mode without track data. So I can never get the empeg to report track titles to the car stereo with it.

- There is that really weird problem where it has the overloaded CPU issue where the audio turns into KrKrKrKrKrkrkrkrkrkrKrKrKrKrKrKrkkkkkk for several seconds. It mostly only occurs after I use the head unit to switch to another source (such as CD) and then back again. But still, that's a bug in the protocol handling, out of my control.

- The workarounds I've done are not 100 percent reliable or pretty, and have some odd behavioral quirks. Such as, the startup/connection time to the bluetooth is longer than it should be, the play/pause doesn't look right on the car touchscreen (it has to always be in "play" mode and then you use the "pause" button to toggle on/off).

- The workarounds don't handle edge cases well, in regards to timing of things connecting/disconnecting and source switching.

So I'm hoping the RN-52 is more stable and I won't have to do any kludgy work arounds, and I can just do a 1:1 translation of input to output without any special case code.