Thanks! Maybe someday I will indeed try to do it sans Arduino and get it working fully internal to the player. But now that I have it working as an external box with all the features I want, I'm going to refine this for now and finalize the current design. In the meantime I'll give you any support you need for doing the internal version yourself.

Here's my thinking at the moment...

If anyone besides you or me ever wants one of these for themselves, then they can have three different ways of doing it:

1. Fully external box which requires no player modifications, uses analog audio plugs. Requires an Arduino and one of the WT32i dev kit boards.

2. External box like 1 above, which can also work with digital I2S connection, but you have to be willing to open up the empeg and solder to the I2S pads and hijack some wires out the back of the docking connector (I'm currently using three of the tuner module wires successfully for this).

3. Fully internal to the player, using the tuner serial lines for command/control of the bluetooth and the I2S pins for the audio, but requires additional connections and soldering internal to the player, and takes up a drive bay slot for the assembly.

I currently have a working implementation for either/both Way 1 and Way 2, and I'm designing my second revision of the printed circuit board already. Once I get that second PCB made and tested, I could be set up for manufacturing these things as complete modules, or selling them as kits. The second revision of the PCB will allow the module to be used in either Way 1 or Way 2.

For way 3, I think that you should totally run with that. You know so much more about programming for the Empeg and you know so much more about EE than I do, I think you'll be totally successful at that. Your version would be smaller, simpler, and MUCH cheaper to manufacture.

I'm pretty excited about this. I know the software is going to need a lot of tweaking though, so there will still be updates to the example code. If anyone else wants one of these, I'll bet that it won't pair up perfectly with their stereo and will need additional code tweaks. Each time I try this thing on a different bluetooth device, I discover some other little thing that doesn't work and I have to update the code again.

Still, having a lot of fun (and stress) with this project. I've been through so many twists and turns with the circuitry, most of which I haven't mentioned on here. Last couple of days it was weird thing with the serial connection failing on the PCB from Pad2Pad which turned out to be just traces grounding out when they weren't supposed to be, and I had to jumper around some shit. Next design from Pad2Pad will have bigger clearance around the traces than their recommended settings. Live and learn.

I'm super grateful for you and for the other folks on this BBS for the suggestions and the help. The initial idea for doing this was from two people: FieroSTI for having made a bluetooth input board for the empeg (the opposite thing of what I'm doing now), and Elperepat for pointing out the original BC127 breakout board at Sparkfun.com. From there it just snowballed. You all have been super helpful with all sorts of great suggestions related to the bluetooth stuff and for the electrical circuits. It's just been amazing. Thanks all!