I was approached by some composers who explained a need for a performance-oriented MIDI fader controller. They and I liked Notes and Volts' take on this concept:
The Notes and Volts design is based on the Teensy, which is difficult to source. I suggested we take the 16n Faderbank design and modify it for longer faders. This was met with a meh response, since having to plug into a PC to reassign CCs is not ideal. I decided quickly to start from scratch.
Client Requirements:
4 or 5 long-ass faders - 100mm+
Able to reassign CCs on the fly, (not like 16n Faderbank where you have to use a PC)
Wide, comfortable spacing between faders
A screen of some kind to show data
Good feeling caps
USB Midi to use with orchestral VSTs
My Additional Selfish Requirements:
Have CV outs
Have traditional MIDI (1/8" or DIN) in and out
Use 7 Segment LEDs because I think they're cool
Fit in a Hammond Enclosure
Use SAMD21G as the main brain
Firmware upgradeability
Open Source
I got to work designing this with 100mm faders in mind. 4 fit comfortably in a Hammond 1590XX, with room on the left and right sides for buttons and LED displays in an unconventional arrangement.
I designed the device around the SAMD21G, but I wanted to use a common arduino bootloader to allow for hacking. I settled on the Adafruit Feather bootloader. This had to be decided early, since that will define which pins I can use, and what additional components are needed (i.e. crystal oscillator).
Update November 14
PCBs have arrived.
CV Outs are on a seperate sub-board connected with a 10 pin IDC cable.
Update November 23
The caps I ordered are not the ones that actually arrived, so I am waiting on another shipment. The final colour will not be this garish yellow, I promise. I'm thinking textured beige/white with baby flue faders and yellow buttons.
Current functionality: assignable midi CCs by holding the left button and moving the slider you wish to change the CC number for. The sliders have been heavily smoothed to have minimal jitter - still needs improvement though once all other features are implemented. Case drill and mill design in Fusion 360 is good, tested using 3d printing. I'll be ordering metal enclosures soon once I have some art inspiration. LED displays can show the current CC being sent, and show helper text using a rudimentary alphabet font. Display times out after 4 seconds and goes to sleep unless a fader is moved. The back panel includes a USB C connector along with 4 CV outs, 1 traditional MIDI In and 1 MIDI Out (both 1/8" standard to keep size at a minimum). Switch on the inside to select between 1/8" midi standards A and B.
Easy firmware upgrading is implemented - a button on the inside needs to be "double clicked" while connected to a PC, and it will appear as a USB flash drive, onto which you can drag and drop a new firmware file.
To Do: Right button will change MIDI channel, in the same way as left changes CC.
Along with CCs I'd like to be able to send Pitch Bend and Program Change messages as well.
Holding both buttons at the same time will enter an options menu, allowing changing of
1. LED Brightness (value from 0 to 100%)
2. Left Button Assignment (Some musicians may want to send a note on/off with the two buttons, or program change up and down)
3. Right Button Assignment
4. Fader inversion (max at bottom instead of top).
Implement settings memory so your assignments are kept when power is disconnected.
Heavy Testing
Hardware Issues: This rarely happens, but the hardware only has 2 very minimal bugs (that I've found so far). The CV outs are out of order - out #4 is in the position of Fader #1 etc, and one MIDI A/B switch is backwards. This will be solved with a custom cable for these 5 units, and the mistake will be fixed for production.
Next Steps: Design and order Hammond enclosures. Finish implementing features. Will update with final product photos in a few weeks.
I plan on releasing this as a DIY kit (you solder it yourself, SMD parts preassembled and microcontroller flashed) with an optional charge to have me pre-assemble and test the device. Cost will be $180(CAD) for the kit, and $230 fully built.
These first 4 units however, I'd like to sell at $100 built and tested to folks that could give me feedback and suggest improvements. Like I mentioned, it is very easy to upgrade the firmware so once we have a feedback cycle going I can email you a new firmware for any suggested changes. I need to get this device in the hands of musicians to find the nit-picky details that will really make Fade4 shine. Please email me - fil@cctv.fm - if this device interests you.