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So... what's my problem, anyway?

A project log for Tannerino

Arduino Electro-Theremin (slide theremin), with MIDI output and a 8-bit sine wave oscillator

urishaniuri.shani 04/22/2018 at 22:000 Comments

As I wrote before, the Tannerino will be a slider MIDI controller for monophonic (or pseudo-polyphonic) tone generation. I plan on making the slider about 60 cm long, and make it produce continuous notes over up to 4 octaves. Initially, I thought of just providing a center note with a pitch-bend cc, as I found out that pitch-bend can provide up to 24 semitones up or down. This was also the reason I decided to go with an external 16 bit ADC, as the pitch-bend cc is also a 16 bit number. But, I found out later that most synthesizers can only do (+) or (-) 2 semitones. So, here's one problem I'm facing. The other problem I have in this design is the integration of a switch in the slider. In some of the versions of the original instrument, there was a switch located on the slider, which turned on the sound output of the oscillator. I thought of having a ribbon cable dangle from the slider, but that doesn't seem like a long-term solution, as it will probably just crack with material fatigue over time. Third problem, which came up while testing my initial firmware with a menu over an LCD, was with the tone generation. Without the LCD, the sound was continuous and (thanks to the nature of a clean sine wave) quite boring. But when I added the LCD, the sound was jittery and the sound was more like a cricket. So, to recap, I have three design problems / goals:

  1. Make the MIDI output a continuous one when gliding through different notes.
  2. Find a way to have a mechanical switch, actuated by the player while sliding through notes, and placed on the slider itself.
  3. Get a consistent sound output going while still having a menu based UI, as well as MIDI generation.

So, solving the first problem will, I suppose, require some interpolation of the current location of the slider, and sending a MIDI note with relative pitch-bend cc.

The next problem is more of a mechanical problem. I thought of maybe having a T-shaped bracket with contacts on both sides, but that still requires some investigation.

The third problem (which is probably far from being last), requires some investigation into what actually happens when the note is played. I got a kit oscilloscope with the boards I designed for my other project, and hopefully I can figure out what's up with that once I get the scope going. 

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