SimpleSeq MIDI Sequencer

August 7, 2011

Overview

SimpleSeq is a MIDI sequencer designed to be used as an instrument or drum machine. It can trigger notes and sounds on a synthesizer, VST plug-in, or any sound generating device that supports the MIDI protocol.

Time Invested: 3 weeks
Cost: $15
Features:

  • Two-note polyphony
  • Velocity control for each note
  • Tempo control
  • Pitch shifting
  • 8 and 16-step sequencing
  • 8 assignable MIDI CC controls

Video

Details

This project is based off of Michael Roebbeling's SimplenZAR, which I modified and made my own. Below is a list of changes I made and features I added.

For the circuit, I...

  • Added a second button for navigation
    - [left]-[enter]-[right] instead of [select]-[enter]
  • Embedded the microcontroller and power supply into the circuit
  • Used brighter LEDs with 220 Ohm current-limiting resistors

For the firmware, I...

  • Rewrote the "loop" section of the code, so the device is constantly checking for user input (every 10ms), not just when notes are played
    - the original device would "freeze" in between every note, which became a major problem at slow tempos
    - from what I now understand, what I did was essentially event-driven programming
  • Added the ability to navigate forward and backward through steps and menus
  • Added the ability to play two notes simultaneously (aka. two-note polyphony)
  • Added the ability to store presets in EEPROM (three total)
  • Added the ability to control eight MIDI CC functions (eg. filter cutoff frequency, resonance, portamento, etc.)
  • Added the ability to mute all notes
    - helpful when assigning MIDI CC functions in Ableton, etc.
  • Changed the way tempo is set (using BPM, rather than milliseconds of delay), and constrained the range from 60 to 300 BPM
  • Changed the way new notes start when added to a sequence
    - repeats the previous note, instead of always playing a C
    - this keeps the user from hearing a wrong note when C is not in-key
  • Simplified parts of the original code

The sequencer is still breadboarded and looks pretty ugly ever since I embedded the microcontroller, but it works just fine. You can find the source code and a hand-drawn schematic of the circuit below.

Gallery

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Source Code:

Download

Schematic:

Download

License: CC BY-SA 4.0 Deed - You may copy, adapt, and use this work for any purpose, even commercial, but only if derivative works are distributed under the same license.

Category: Software, Hardware