When last we visited the oMIDItone project, the plan was to turn the test code into a class, and add more heads to allow for a wider range of pitches to be played at once. Sounds simple enough, but it took a lot longer than I ever thought it would, with many complications and lessons along the way. I'll go over everything in roughly the order it happened in, starting with code challenges, then moving on to hardware challenges, and finally the (more or less) working prototype. Hold on to your hats, as this post is almost as long as it took me to build the damn thing.
I recently taught a class about using Teensy as a USB game controller input for your computer. It's about an hour and a half of me rambling about how to connect various inputs, how to use the Teensy USB libraries, and going over example code.
I recently received an Otamatone as a gift. I quickly found out I lack the training to accurately hit notes by ear. As a solution to my lack of skill, I decided to modify my Otamatone into a MIDI-controlled instrument. This is the story of my first attempt at doing so.
My friend Marv was selling some 4x4 mechanical keyboard kits, and I drew up laser-cut acrylic cases for them. The first case is for the original design which used an arduino micro. This turned out to be a difficult-to-track-down MCU, and another friend dvdfreitag has made a new version which uses the much more readily available Pro Micro for the MCU.
I made a laser-cut acrylic case for my LimeSDR Mini. CAD Files below. I also installed an FM filter. You can see the comparison before and after on the ameteur 20m band, and boy does it make a world of difference.
I made a very simple 20m dipole. It's two lengths of wire connected to an SO-239 connector in a PVC enclosure, and tied off to the swamp cooler on top of my roof and a nearby tree.