The Open Woodwind Project

An Electronic Aerophone with Wireless MIDI and Onboard Synthesizer

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I'm re-opening the development of my electronic aerophone. Stay tuned!

An Open Source Electronic Aerophone Project.

  • Analog Waveform Shaping and IMU Vibrato

    J. M. Hopkins06/14/2018 at 03:14 0 comments

    Give this a listen... Not bad for a MIDI controller!

    A thumb button activates vibrato/pitch bend mode, where once the gate is active maps z axis acceleration to pitchbend. On top of that, when the keep is pressed, the instrument angle is stored, and a 5 degree dead band created. Any instrument angle inside this dead band just allows vibrato via acceleration, outside this dead band it activates the traditional pitch bend.

    This allows one thumb key to gate vibrato while still having full pitch up/down control.

  • Onboard Synthesizer Testing

    J. M. Hopkins06/10/2018 at 23:26 0 comments

    Utilizing a DSP-1 sound chip.

  • More Testing

    J. M. Hopkins06/04/2018 at 19:22 0 comments

    Most features are working great now:

    Including some interesting fun with the IMU:

    And a little more subtle on the IMU mapping:

  • Prototype Working

    J. M. Hopkins05/30/2018 at 03:30 0 comments

    This weekend was very successful and allowed me to complete a preliminary prototype that has working touch and breath sensors. It is currently a plywood spacer sandwich, but keep in mind that this is for validating the capacitive touch sensors and fingering system.

    The main microcontroller is a Cortex M4 development board from PJRC, the Teensy platform. Touch sensing is done via two MPR121 breakout boards.

    Furniture tacks are used as keys, and the Freescale pressure sensor allows for breath pressure sensing.

    And here's an example of the instrument being played with Reason as the main synth:

  • Main Loop

    J. M. Hopkins05/14/2018 at 04:03 0 comments

    void loop() {
    	if(state == STATE_NOTE_OFF) {
    		if(breath_measured > breath_threshold) {
    			breath_time = millis();
    			state = STATE_NOTE_NEW;
    	if(state == STATE_NOTE_NEW) {
    		if(breath_measured > breath_threshold) {
    			if(millis() > breath_time + breath_risetime) {
    				cc_time = millis();
    				state = STATE_NOTE_ON
    		} else {
    			state = STATE_NOTE_OFF;
    	if(state == STATE_NOTE_ON) {
    		if(breath_measured > breath_threshold) {
    			if(millis() > cc_time + cc_delay) {
    				cc_time = millis();
    			if(note_fingered != note_playing) {
    				if(legato) {
    					note_temp = note_playing;
    				} else {
    		} else {
    			state = STATE_NOTE_OFF;
    void updateNote() {
    	note_fingered_debounce = rawNote(); //Update from capacitive touch board
    	if(note_fingered_debounce != note_fingered) {
    		if(note_debounce) {
    			if(millis() > note_debounce_time + note_debounce_delay) {
    				note_fingered = note_fingered_debounce;
    				note_debounce = false;
    		} else {
    			note_debounce_time = millis();
    			note_debounce = true;

     In the above snips of code you can see the main microcontroller loop, and the updateNote() function.

    It's a dead simple state machine with only OFF, NEW and ON states. Every cycle of the loop we read the raw breath, update our fingered note, and calculate CC values. 

    The full version will have functions for the different programming modes and extra features, but the heart of the instrument is this loop.

  • Component Selection - Capacitive Touch

    J. M. Hopkins05/12/2018 at 08:35 4 comments

    Previous Design
    In my previous prototype I accomplished touch sensitive keys via a pulsed AC signal being amplified by Darlington paired NPN transistors, clocked by a shift register one at a time into a single digital pin on a microcontroller. While this worked, it required quite a bit of soldering, testing of components, and programming.

    Planned Design

    In this next prototype I will be utilizing a true capacitive touch controller to provide key values. The MPR121 from Freescale was chosen for its 12 channels of capacitive touch and I2C communications. Two of these will be used on the same bus and will provide the microcontroller with 24 channels of touch feedback.

    Easily accessible libraries allow for easy programming with the touch data. 

    Example Programming

    MPR121 touchA = MPR121();
    uint16_t keysA = touchA.touched();
    if(keysA & (1 << 4)) {
        //Button Pressed

  • 2018 Update!

    J. M. Hopkins05/09/2018 at 09:22 0 comments

    It's been a while!

    Over the last two years I've moved across the country and started a new time-demanding job at SpaceX, and I've had little time for my side projects between work and family. I am re-opening this project for active development however due to my recent interest in modular synthesis, and of course because I do love playing my Akai EWI. 

    New parts are on order, and I'll be stepping through another development process to get my instrument up and running.

    I'm moving away from a high beta transistor amplified resistance touch sensor strategy to the more common capacitve touch strategy, and will be trying to get my pressure sensitive keys working.

    An onboard analog synthesizer as well as pitch and gate voltages will be available (for eurorack modular synthesizers), as well as hardwired MIDI and wireless MIDI options.

    After the instrument is up and running and I'm happy with it, I will finalize schematics and requirements and place an order for PCB fabrication at which time if others are interested can probably get a board or two for themselves to build their own instruments as well.

    During the development process I'll post code snippets and hardware explanations, so please, follow and keep updated!

  • Super Mario Theme

    J. M. Hopkins06/20/2015 at 01:58 0 comments

  • Onboard Synthesizer Demonstration

    J. M. Hopkins06/15/2015 at 12:20 0 comments

  • OLED Display and Body Progress

    J. M. Hopkins06/11/2015 at 02:09 0 comments

    Sorry for the lack up recent updates, life gets in the way of hobbies too often versus what I'd prefer.

    My camera had a difficult time photographing the OLED Display, but in real life the .96" screen is super bright and clear. You can see the quick and dirty debug screen currently in use, and understand it has full graphics capabilities.

    Here is a test body with the new pressure sensor being calibrated. Conducive copper tape is used to sandwich a physically variable resistive polymer that is in place under the individual keys.

    I hope to have a full bodied prototype done shortly, which will pave my way forward to the eventual kickstarter and open source release. Stay tuned!

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Enjoy this project?



sacha.elijah.duprez wrote 06/12/2018 at 16:42 point

Woah, just discovered what you're doing. I'm very surprised by the quality of the sound, especially concerning the low notes : I like it ! 

Do you plan to improve it again ?

  Are you sure? yes | no

J. M. Hopkins wrote 06/14/2018 at 03:19 point

Thanks man, yes there is still quite a bit of development going to take place.

  Are you sure? yes | no

Johan Berglund wrote 05/14/2018 at 17:21 point

Great to see you are picking this up again!

  Are you sure? yes | no

J. M. Hopkins wrote 05/15/2018 at 06:16 point


  Are you sure? yes | no

Johan Berglund wrote 06/06/2016 at 18:26 point


Thanks for your replies! Thinking of putting the dsp-G1 in my Casio horn if I get to modifying it. Then I won't be missing the pitch bend functionality, as it didn't have it to begin with :) Portamento will still be missed though... but then again I get a key free for other things, like a bis key perhaps. Anyway, thanks again, and I hope you get time to proceed with your Aerophone project soon!

  Are you sure? yes | no

pietkamps wrote 01/19/2016 at 20:31 point

Hi Hopkins, I am interested in how you made the bite sensor or what hardware you have used.

  Are you sure? yes | no

J. M. Hopkins wrote 01/20/2016 at 12:15 point

I've used simple FSRs mostly.

  Are you sure? yes | no

edil07 wrote 06/06/2015 at 20:30 point

Hi Hopkins, I am very interested in your work and thinking of implementing it during my vacation at work in case you have already released it as open source.
Have you considered using Moteino ( as the microcontroller since it provides wireless 

  Are you sure? yes | no

J. M. Hopkins wrote 06/06/2015 at 23:38 point

Hello, as of right now there's not been a release of code, but I can release some of it through my Open Woodwind Project.

There are a few microcontroller options with built in wireless, but I've opted to use separate devices for more flexibility in transceiver choices. 

  Are you sure? yes | no

Gwendolyn Scogin wrote 06/05/2015 at 17:36 point

I am curious as to what hardware you are using for the breath pressure sensor.

  Are you sure? yes | no

J. M. Hopkins wrote 06/06/2015 at 23:39 point

It's an MPX2010GS. I'm still developing this project, but just taking a bit longer than I was hoping for. Being active duty military with a family eats a lot of time. 

My software and hardware will all eventually be released as open source under the Open Woodwind Project, which I assume you'll find interesting :)

Also, I'm now using a Teensy as my primary microcontroller... Good stuff.


  Are you sure? yes | no

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