I was thinking the same thing, in that I should get a small rectangular PCB to mount the Nano and the AD5204 onto.
One question about linking the Nano to the future MIDI interface: Will I be able to use the USB port on the Nano to do bi-directional communication with this separate I/O device? Or is the USB port limited to programming the Nano?
For the MIDI interface box, I was thinking another Arduino with a 5-pin DIN jack for receiving commands from the MIDI network, some way to store around 50 presets, ability to send preset information to the pedal's Nano, ability to receive information from the Nano inside the pedal for creating new presets, a mechanism for manually selecting preset numbers and storing current parameters, and some sort of visual indicator of selected preset number (small LCD I presume). I'm not so concerned about designing this piece yet, I just want to plan ahead with respect to how I'll interface it to the Nano inside the pedal.
I'm hoping the two could transfer data to each other VIA the integrated USB ports and not require direct connection to the pins on the Arduino. If I can do this, mounting it will be easier, as I can just notch the pedal's enclose to expose the USB port on the side. If it has to be attached to pins on the board, it'll add complication to the pedal's enclosure.
So for a shopping list, I've got:
- Arduino Nano - https://www.amazon.com/Gikfun-ATmega328-Micro-controller-Arduino-Ek1620x1/dp/B00Q9YBO88
- AD5204 board - I can't seem to locate where to buy one of these? I'm finding single digital POT boards, but not the 4 or 6 multi POT ones. Any suggestion?
- PCB board - Something like this https://www.amazon.com/Paxcoo-Double-Sided-Board-Prototype/dp/B01M7R5YIB
- Jumper wire - Which I already have
Then I'll need someway to tap 5v off of the pedal's incoming 9v power supply. I haven't thought through this yet though. I'll need to step it down from 9v to 5v somehow, but considering the current is so low, I assume it'll be fairly simple? Unless there's an Arduino board that'll accept 9vdc and be small enough to fit ...
Thanks again for your input, it's been a great help!