A simple firmware MIDI sequencer program for an Arduino board with a SparkFun MIDI Shield or equivalent
This is an Arduino "sketch" (project), intended to be compiled using the free Arduino development software. It is intended to be run on standard sized Arduino boards such as the Arduino Uno, with a daughter board.
This sketch provides a fully functional MIDI sequencer, and is designed to work with the SparkFun MIDI Shield. The shield has MIDI In, MIDI Out, three buttons and two potentiometers (knobs you can turn).
If you hold the shield with the MIDI connectors at the bottom, the buttons, from left to right are Play, Stop and Record. The knobs, again from left to right are Tempo and Velocity.
The sketch comes up with the sequence from Pink Floyd's song On The Run (from the Dark Side of the Moon CD), which is legal "fair use" because I am providing it for educational purposes only. It's only 8 notes, which are listed on the Wikipedia page for the song, so I'm not revealing any secret musical arrangement.
The sequencer plays a sequence of MIDI notes when you connect the MIDI Out of the shield to the MIDI In of a synthesizer and press the Play button. All the notes have an equal duration. The green LED on the shield will light while it is playing.
You can input a different series of MIDI notes to the sequencer to play by connecting the MIDI Out of a keyboard (or other MIDI instrument) to the MIDI In of the shield. Note: There is a switch on the MIDI Shield, and for inputting notes, it must be in the Run position; for writing a sketch to the Arduino, it must be in the Prog position.
To change the sequence, make sure the playback is stopped, press the Record button, and the red LED will light. Then play the notes you want in the order you want them played. When inputting, you do not need to play fast or even, just in the right order. If you make a mistake press the Stop button and start over. If you complete playing the sequence in the correct order, press the Record button again. it will immediately begin playing your new sequence.
The circuit for the MIDI shield can be found here: https://www.sparkfun.com/datasheets/DevTools/Arduino/MIDI_Shield-v13.pdf
The sketch uses a timer library created by Simon Monk and Jack Christensen. You can find it here: https://github.com/JChristensen/Timer
There is an out-of date page about it on the Arduino website here: http://playground.arduino.cc/Code/Timer
Follow the instructions at the github site about unzipping the library in your Arduino library folder, and if necessary, from inside this project, select the menu Sketch->Import Library and import the timer library.