Spent a few days creating a schematic to contain my current protoboard project, with some other additions I'd like to try when the parts come in. 

Right now the board is at 96x156mm, which is a bit big. Its constrained by the kindle battery I've chosen, so we'll see if its a good fit for the hands.

Right now it has the bare minimum for user input. I last minute added an SI4720 for some radio stuff, a mic input, and alternative (and most likely better) designs for battery management/boost converter. They're taken from adafruit's powerboost 1000c, which is a proven design. I tweaked some of the regulators based on what I have in stock. Added a USB wifi card (MT7601U) I found on aliexpress, which is supported in the mainline kernel. Makes ad-hoc UDP-OSC multicast stuff seem more plausible, too.

Unfortunately Friendlyarm raised the price of their nanopi neo core boards from about $9.99 to $18. Not too big a deal for one, but I'm making a few for my friends. Bummer. 

After I sent this off to jlcpcb, I decided to try my hand at a "what if" situation, and designed some of this synth in the style of the 1 square inch contest. I figure I could take a modular approach, so if you wanted, say, a 4 in/ 4 out soundcard, you could plop a tiny PCB on to your main PCB and be off to the races. Right now I've got a decent audio mux, the RF transceiver, a PCM2906 2in/2out soundcard, and an FE1.1s usb hub each on their own < 1 inch PCBs. 

I'm envisioning a sort of main bus backbone, eurorack style, on the main or carrier PCB, with room for all these little 'expansion cards' so the end user could build the synth they want. This'd make adding more buttons/knobs on the top easier, too, as you could create a PCB to mount to the front and hook into, say, a USB or UART interface.