Originally Posted By: tfabris
What can we do to prevent other people from making the same mistake and frying their stuff too?


Its not just I2S, but also the serial RX/TX pins in my case.

We can add circuitry inside the empeg to tristate the I2S outputs when Bluetooth is not connected. This would consist of some MOSFET transistors and a resistor or three, plus a signal to enable those outputs when needed. The tricky bit is, from where do we get that signal? It can be software controlled once I find a spare output pin somewhere, or manually controlled with a switch/button.

Or perhaps something more passive might work, such as diodes to prevent reverse current on those pins. That's easy enough for the empeg, but something similar should be done for the tuner as well: perhaps inline diodes on the tuner's half of its wiring harness. Nice and safe then, just need to ensure the voltage drop (from the diodes) isn't excessive.

Quote:
The new scheme will have IISC on the originally unused purple wire, so there's no danger there for that one. IISW and IISD1 will be on Tuner Level and Tuner Signal. I wonder if that might fry the tuner but not the empeg if they did that?


Could fry either/both. I think diodes might be the way to go.

Or, just put the new/smaller BT breakout module inside the empeg, so that it doesn't need I2S connections on the tuner wires. Will still have to do something similar for the serial connection though, either MOSFETs or diodes to prevent the same issues on those wires.

I'll be on Christmas break starting three weeks from now, and hope to take a really good look at things then. Perhaps there may be a feasible way to add another dedicated serial port to the empeg for just the BT module.

One crazy scheme bouncing around in my skull is to stuff an ESP8266 module inside there, and perhaps connect to the the empeg via a 4/8 bit parallel connection by plugging into the IDE cable. That would give enough bandwidth for comms between it and the empeg, and then it could easily manage most of the BT housekeeping duties on its own.

If you haven't yet discovered the ESP8266, well.. it's a nice fast micro-controller with built-in WiFi-N, 14 I/O pins, tons of RAM and flash memory, and can be programmed using the Arduino tools/libraries. It's also about the size of a small postage stamp, though it gets larger once soldered to a breakout board (similar to the BT breakout you found).

A nice side effect of embedding one of these, is that we could also use it to give the empeg a WiFi interface. smile