A friend and I have been talking about getting into DSP effects for a while and recently picked up a couple of Blackaddr's "Teensy Guitar Adapter" boards (I'm just going to refer to them as "Blackaddr boards"). I figured I'd do a build thread as we go along since I don't think many people know about the Blackaddr boards.
This pedal is primarily intended to be a developer platform for our needs. So it's big, has lots of knobs, and a small OLED display. We settled on the Hammond 1550G enclosures (roughly 8.5" x 5.75"). They're huge but I didn't want to get backed into a corner since the Blackaddr boards while electrically quite sound aren't really designed to cram into tight spaces.
Here's what I've modeled up so far:


I opted to put the Blackaddr board upside down since it's got quite a bit on its underside (which I haven't modeled in any detail) and mount it by its 1/4" jacks.
With 7 knobs, 6 switches (the knob by the display is also a button), and an I2C display we are way, way out of bounds from what the Blackaddr board brings out to its headers. It has 8 pins that it exposes from the Teensy and only one of those is an analog input. So I'm going to use an analog mux for sampling all those inputs.
I found some Neopixel type LED's in a standard 5mm "hat" LED form factor which I'll be using for the indicators since we would otherwise be short one pin. I may throw some more LED's on there somewhere.
[Note: there are lots of pins on the Teensy that aren't exposed, we could tap those if needed. I’m trying to make this easy plug together. ]
Well that's all for starters. Oh, well, one concern I have is the Teensy will be quite busy doing audio processing. I’m a little worried about it driving Neopixel protocol which also has a real time requirement. Worst case I think I just drop another Arduino of some type in the box and hook it up on the I2C lines.