Had less time to work on this today, as I kept getting side-tracked on other projects. I did manage to move away from a breadboard and tangle of wires to a more organised system. Everything is on one piece of proto-board, into which I plug my teensy-LC, the motor drivers and the wires going to the electrodes. Just for fun, I used point to point wiring and solder blobs to make the board look a bit more interesting. Ok, so not just for fun - didn't have time to etch a PCB :D

Here it is:

I got code working that reads the values from each electrode through the 4051 multiplexers, but I still need to work out how to simultaneously generate a signal and send that out. DMA should be possible but I have almost no experience with that. Anyway, Here's a video because I'm experimenting with that too:

The video compression makes it look bad but 9 megs vs 180 made uploading feasible. Now it's just tidying up, adding the second set of electrodes, insulating stuff and writing a lot of code. easy, right?