This is a hardware-interface vor voctomix, developed late 2017 and tried in a few talks at 34c3.

Key features are:

• Custom PCB
• Cherry MX switches with custom 3D-printed keycaps
• 3D-printed top and bottom enclosure parts “sandwiched” around the PCB
• Arduino Nano which sends commands to a computer via USB
• Computer relays the commands to the voctomix software via socat
• is supposed to learn to speak TPC on its own (was not implemented on 34c3)

This is a community project with help from many friends.

The keycaps are gothic.FCStd, 20 * 33,5 mm for the composite mode buttons and 25 * 25 mm for the camera/channel buttons and the take button. Please adjust the side lengths in the spreadsheet of the file, but there are also stl files in the ‘case’ folder.

Lessons learnt after PCB production V 1.0:

• slightly wrong footprint for resistors, too short
• wrong footprint for cherry switches, contacts for LEDs are too far apart
• the Cherry MX I got from reichelt.de aren’t for PCB mount, be more careful when shopping
• wrong footprint for StreamOn switch, fix: bend up two diagonal contacts
• 1.5k ohm pull-up-resistors are required between A4 and 5V and A5 and 5V
• the buttons would look more evenly illuminated if the LED was behind the switches -> turn the Cherry MX around 180°

See here for a photo with hardware fixes.

Lessons learnt regarding the case

• I’ve actually included small changes into the file after printing, print as-is, and slice everything the way around it is supposed to end up. Yes, printing the buttons upside down would be faster but looks ugly. I found it easier to remove the support-material when the buttons were printed with raft.
• Print everything with transparent filament and then paint up the upper side of the case (except from the letters !!!) with a dark-ish pen that isn’t water-soluble. Due to the LEDs inside, the letters become illuminated.

Shopping list

• 1 arduino nano (clone)
• 1 ethernet-shield for arduino nano
• 12 Cherry MX switches with holes for LEDs, for PCB mount. I used ‘clear’ and would go for ‘brown’ next time.
• 12 3mm LEDs, 4 red, 4 blue, 4 other color (yellow). alternatively there are probably special LEDs für Cherry MX but I didn’t have the time for searching
• 1 tact switch for StreamOn-button
• 1 5mm LED red
• 1 5mm LED green
• 14 resistors 220
• 13 resistors 10k
• 2 resistors 1.5k
• 4 nuts and bolts M3 (best: screws with countersunk head)

Status

One device has been built so far and has been successfully used in a few talks on the 34th Chaos Communication Congress.

References

• Cherry MX keycaps
• Geekend Prototype
• Voctoknopf as a handheld controller