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MIDI Drum Machine
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selected Features
Photos
Schematic
Circuit Board Layout
Firmware
MIDI Protocol Details

MIDI Drum Machine Features

  • Eight Velocity Sensitive Pads
  • Fast Response, approx 1 ms (plus 2 or 3 ms for MIDI Note-On message transmit)
  • Eight Configurable Parameters per Pad (64 total)
  • All front panel configuration available while playing, no special modes
  • Channel Parameter, which MIDI channel a pad sends onto
  • Bank Parameter, set which voice bank, for some mulit-bank synth
  • Voice Parameter, set what sound will be played
  • Note Parameter, what note (pitch) will be played
  • Harmonize Parameter, TODO: what did this do...
  • Threshold Parameter, TODO: what did this do...
  • Sustain Parameter, how long will the sound last
  • Limit Parameter, TODO: what did this do...
  • "All Notes Off" Button

Front Panel Operation

drum machine illustration

To adjust parameters, the user presses the Pad button to select which pad to configure. The one of the 8 LEDs arranged in the shape of the pads lights to indicate which pad is selected. The Option button is pressed to select one of the 8 configurable parameteters, indicated by the 8 LEDs on the far right. At all times, the 3 digit display shows the configured value of the select option and pad. Pressing the Up and Down buttons increments and decrements the value. By using this simple interface, each pad to easily to configured to play a custom sound from any synth connected to the MIDI network. typical system connection diagram

MIDI is Required

This simple diagram shows how the MIDI Drum Machine would be used. It only produces MIDI output messages. There is no direct audio output. The MIDI network (red lines) requires synthesizers to receive the MIDI commands and play sounds, which are typically mixed (plus symbol) and of course amplified. Of course, more complex systems are possible. The key point is that this drum machine only prodives MIDI output messages.

TODO: Create some pages that explain the bits and bytes of MIDI, and specifically how they are used by this project.

TODO: Add a section about the other cool features that were planned but never got implemented (MIDI merge, interrupt driven serial I/O, other things I probably don't remember anymore). Most of these ideas had provisions in the firmware and hardware, which should be explained somewhere.

Take a look under the hood.


The MIDI Drum Machine, Paul Stoffregen and Rod Seely.
Designed and constructed Fall, 1991. Project status: Complete.
http://www.pjrc.com/tech/midi-drums/features.html
Last updated: February 24, 2005
-- These drum-machine web pages are still under construction --
Questions, Comments?? <paul@pjrc.com>