Sunday, October 08, 2017

Four Channel Control Voltage to MIDI CC

This is a very simple four channel control voltage to MIDI CC converter. This device scales positive voltages, then limits positive and negative voltages, before being converted to a digital value and sent as a USB MIDI continuous controller message. Note that negative voltages are simply clipped.

This data can then be used to map control voltage signals to digital software.

In the example video, four control voltages from an LFO, an ADSR and two channels of Maths are converted to MIDI CC messages and mapped to parameters in Lumen.



Download the code here:

Example Video

Friday, October 06, 2017

Progress on Eight Voice USB MIDI to CV

Yesterday I made this eight voice USB MIDI to CV interface. Bus powered, with each voice corresponding to a MIDI channel. Each voice currently has a note gate, pitch CV and velocity CV. All outputs are buffered. The gate is 5V. The pitch has a range of just over four octaves. Tuning seems relatively stable.

I would like to add a 'mode' control, where one of four modes can be selected:

  • Melodic mode: Eight melodic voice outputs; each voice has note gate, pitch CV and velocity CV
  • Rhythmic mode: Eight drum voice outputs; each voice output has note gate and velocity CV; plus eight CV outputs that are assigned to MIDI CC
  • Mixed mode: Four melodic voices; four drum voices; plus four MIDI CC CV
  • Gate mode: Eight note gates; plus sixteen CV outputs that are assigned to MIDI CC
  • High resolution mode: Eight note gates; plus sixteen CV outputs that are assigned to pitch bend

Stay tuned!

Tuesday, October 03, 2017

New Me-ism: Monthly Wrap Up - September 2017

Cross-posted from New Me-ism


September was a mixed bag.


Even though I generated more waste than in August, I did get a chance to try out dehydrated food extensively by hiking for seven days total throughout this month at Baroota and the KIWT.

Here's my rubbish for this month:

Far too much plastic! Damn.

Monday, October 02, 2017

Comparing Optomix Vactrol Response

A comparison between channel 1 and channel 2 of my Optomix module, in terms of using the 'strike' input with a 20ms 5V gate.

Sunday, October 01, 2017

Mixed-mode USB MIDI to CV

This is a simple mixed-mode USB to MIDI device. Mixed-mode because it supports both pitched and percussive sounds.

MIDI channels 1 - 4 are mapped as monophonic data to Pitch Control Voltage 1 - 4, Velocity Control Voltage 1 - 4 and Note Gate 1 - 4. These are suitable for controlling melodic synthesisers with pitch and velocity being mapped to different parameters, and the note gate triggering an envelope.

With MIDI channel 5, MIDI note 60 is mapped to Note Gate 5, MIDI note 62 is mapped to Note Gate 6, MIDI note 64 is mapped to Note Gate 7 and MIDI note 65 is mapped to Note Gate 8. These are suitable for triggering percussive sounds.

The range of the pitch output is approximately 5 octaves. Velocity is mapped to a voltage range of 0 - 5 volts. The note gate outputs are 0V for note off, and 5V for note on.

A set of four MCP4922 dual DAC chips are used. These provide 12-bit accuracy with a buffered output. A 100 ohm resistor is used between the DAC output and the CV output for pitch. A 1000 ohm resistor is used between the DAC output and the CV output for velocity. Each gate output pin is routed directly from the Teensy to the gate output socket via a 1000 ohm resistor.

The code works for Teensy 2.0 and 3.6, as well as other models. Simply adjust cs_offset (for chip select offset for the DACs) and gate_offset (for gate pin offset), and route the pin outputs accordingly.

More information about connecting an MCP4922 can be found here.

These are ideas I am still fleshing out. Once I am happy I will make a more in-depth tutorial, covering the setup and mapping in more detail.

In the meantime, download the code so far here: