The MIDIsonar is a MIDI Gesture Controller based on an Arduino UNO with two HC-SR04 ultrasonic sensors.
With MIDIsonar you have two independent sonar based gesture controllers that let you create music by waving your hands up and down above the controllers.
Each gesture controller uses a ultrasonic sensor that measures the distance between itself and the hand above it using sonar waves (much like bats do to orientate themselves).
By varying the distance between your hands and the ultrasonic sensors you generate musical information that can be send over the MIDI Out to any MIDI capable device like your synthesizer, drum machine or DAW.
MIDISonar lets you generate the following MIDI information:
- MIDI Control Changes - Change the sound characteristics:
- Selectable MIDI CC number.
- Selectable value range (min and max).
- MIDI Notes - Play melodies and scales:
- Selectable root note.
- Selectable scale (12 different available)
- MIDI Chords - Play harmonies and progressions:
- Selectable root note.
- Selectable chord progression (9 different available)
- MIDI Pitchbend - Change the tone height of the sound:
- Selectable direction (up, down, up&down).
- Selectable value range (min and max) and neutral zone .
For both controllers the following settings are available:
- Active status:
- Set the controller active or not so you can use both or either one of the controllers.
- Operational range:
- Set the range (minimum and maximum) in cm's in which the controller is operational (from 5cm to 80cm).
- Polarity:
- Set the polarity of the controller, e.g. CC values increase or decrease when your hand is raised.
- MIDI Channel:
- Set the MIDI channel of the controller so you can use both on the same or on different MIDI channels.
If set to two different MIDI channels the MIDIsonar can e.g. be used to:
- Play chord progressions with the left hand controlling a pad sound and play note melodies with the right hand controlling a lead sound.
- Control the filter of a running sequence sound with the left hand and play note melodies with the right hand controlling a lead sound.
If set to the same MIDI channel the MIDIsonar can e.g. be used to:
- Control the filter of a sound with the left hand and control the resonance of the same sound with the right hand.
- Control the volume of a sound with the left hand and control the pitch of the same sound to play the sound like a theremin.
- Trigger a single bass drum note with the left hand and trigger another single snare drum note with the right hand to play air drums.
You can build the MIDIsonar yourself. Just build it up like shown below and load the MIDIsonar.ino into the Arduino UNO.
Connect the various components as shown in this schematic diagram.
To build the MIDIsonar you need the following components.
| Component | Quantity |
|---|---|
| Arduino UNO Microcontroller | 1x |
| HC-RC04 ULtrasonic sensor | 2x |
| HD44780 16x2 LCD screen | 1x |
| MIDI Din Connector | 1x |
| Push buttons | 5x |
| LED diode | 2x |
| Potentiometer 10kOhm | 1x |
| Resistor 220Ohm | 5x |
| Resistor 10kOhm | 5x |
| Breadboard & Wires | 1x |
If you want to build a more permanent solution you might want to solder the components and you additionally need protyping PCB boards and soldering equipment.
If you want to build it into an enclosure you might additionally need wood, paint and screws (wooden enclosure or 3D printing equipment (3D printed plastic enclosure).
The MIDIsonar defines the GPIO pins of the Arduino UNO as follows.
| GPIO | Usage | GPIO | Usage |
|---|---|---|---|
| TXD | Serial MIDI Out | D10 | Activity LED B |
| D2 | LCD Data bit 7 | D11 | LCD Clock |
| D3 | LCD Data bit 6 | D12 | LCD Register Select |
| D4 | LCD Data bit 5 | D13 | Activity LED A |
| D5 | LCD Data bit 4 | A1 | Button MODE |
| D6 | Sensor B Trigger | A2 | Button PREV |
| D7 | Sensor B Echo | A3 | Button NEXT |
| D8 | Sensor A Trigger | A4 | Button INC |
| D9 | Sensor A Echo | A5 | Button DEC |
In the software the pins are defined at the beginning of the code. If you use another type of Arduino than an Arduino UNO, you might have to change the pin numbers to the corresponding ones for the type that you use.
The software uses the following libraries:
LiquidCrystal.h- to interface with the LCD screenNewPing.h- to interface with the ultrasonic sensors
The software consists of a setup() that initializes the MIDIsonar and displays the welcome message and a loop() that cycles through the three operational modes Standby, Setup and Play.
The software contains the following functions/subroutines:
MODEstandby()- implements the Standby modeMODEsetup()- implements the Setup modeMODEplay()- implements the Play modevalue2string()- converts values to strings for displaying purposesMIDIchord()- play chords by decomposing to individual notesMIDIpitchbend()- play pitchbendMIDImessage()- send individual MIDI message
The sketch uses 15010 bytes (46%) of program storage space. Global variables use 1894 bytes (92%) of dynamic memory.
The MIDIsonar uses a default setup for the controllers. This default setup is loaded when the MIDIsonar is turned on. You can change this defaults if you want the MIDIsonar to start up with a different setup.
The default setup for the two controllers is defined at line 137 of the code.
/* initialize the data array with default values */
int value[2][18] = {
{ 1, 1, 1, 5, 50, 1, 7, 0, 127, 1, 60, 24, 1, 60, 14, 3, 3, 1 }, /* controller A: Active | CC 7 Volume over full range 0-127 */
{ 1, 2, 1, 5, 50, 1, 7, 0, 127, 1, 60, 24, 1, 60, 14, 3, 3, 1 } /* controller B: Active | NOTE Chromatic scale with root C3 with 24 steps */
The settings map to the following:
| Controller | ACTV | TYPE | CHNL | LDST | HDST | POLR | CNTR | LVAL | HVAL | SCAL | ROOT | RANG | PROG | ROOT | RANG | TYPE | NTRL | PBFX |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CC | CC | CC | NOT | NOT | NOT | CHD | CHD | CHD | PB | PB | PB | |||||||
| A | 1 | 1 | 1 | 5 | 50 | 1 | 7 | 0 | 127 | 1 | 60 | 24 | 1 | 60 | 14 | 3 | 3 | 1 |
| B | 1 | 2 | 1 | 5 | 50 | 1 | 7 | 0 | 127 | 1 | 60 | 24 | 1 | 60 | 14 | 3 | 3 | 1 |
The defaults of both controllers are basically the same:
- Both send on MIDI channel 1 (CHNL) with a working range from 5 cm (LDST) to 50 cm (HDST).
- Controller A is set to TYPE 1 which means to send MIDI CC information. So it uses the config for the CC information: sending CC 7 (CC CNTR) over the full range of 0 (CC LVAL) to 127 (CC HVAL).
- Controller B is set to type 2 which means to send MIDI NOTE information. So it uses the config for the NOT information: using the chromatic scale (NOT SCAL) with root note C3 (NOT ROOT) and a range of 24 notes (NOT RANG).
The file MIDIsonar datastructure pdf defines the settings and the values that can be used.
The MIDIsonar's sensitivity can be changed in two different ways: configuring the ping medians and configuring the wiggle room.
The ping medians are defined at line 149 of the code.
/* initialize the data array with ping medians */
int pingmedian[4] = { 2, 3, 3, 2 };
The ultrasonic sensors work by sending a ping and measuring the time until they receive the echo. In order to prevent rogue measurements, it is possible to send multiple pings, discard the out-of-range measurements and calculate an average. The pingmedian array defines how many pings are used for each type of operation: MIDI CC (2), MIDI Notes (3), MIDI Chords (3), and MIDI Pitchbend (2).
Note
Increasing the number of pings makes the measurements more reliable, but also makes the MIDIsonar react slower to the hand movements. So changing the ping medians is an act of balancing reliability vs performance.
The wiggle rooms are defined at line 152 of the code.
/* initalize the data array with wiggle room */
int wiggleroom[4] = { 10, 10, 10, 0 };
The wiggle room is the minimum amount that a new measurement must differ from the previous measurement in order to be processed (in microseconds). This prevents that small movements of the hand or small imperfections in the measurements result in false triggerings. The wiggleroom array defines the wiggle rooms that are used for each type of operations: MIDI CC (10), MIDI Notes (10), MIDI Chords (10), and MIDI Pitchbend (0).
Note
Increasing the wiggle room prevents false triggerings, but also makes the MIDIsonar react less well to small hand movements. So changing the wiggle room is an act of balancing accuracy vs coarseness.
Here are some photo's of my MIDIsonar to give you inspiration to design you own enclosure.
When you power on the MIDIsonar it starts up with the welcome screen that displays the software version.
After a few seconds the MIDIsonar switches to the Standby Mode.
By pressing the 🟥MODE button you can cycle trought the three modes Standby, Setup and Play.
The MIDIsonar has a default setup and you can immediately use it by going to the Play mode. The default setup is:
MIDI controller A:
- Active with a range from 5cm to 50cm, positive polarity.
- MIDI channel 1.
- Sending MIDI CC 7 (Volume) over the full range of 0 to 127.
MIDI controller B:
- Active with a range from 5cm to 50cm, positive polarity.
- MIDI channel 1.
- Sending MIDI NOTES using a chromatic scale with root note C3 divided in 24 steps.
Note
When in Play mode the activity LED's for controller A and controller B indicate whether the controller is active (lit) or not (dimmed).
When in Play mode the LCD screen gives visual feedback on the controls. For the default setup it shows the following information.
You can read from this screen that controller A is now sending CC 7 with a value 32 on MIDI channel 1 and controller B is now sending note G#3 also on MIDI channel 1.
In Setup mode you can configure the settings for both controllers.
When you go into Setup Mode for the first time you are presented the first setup screen for controller A.
The cursor (a thin line at the bottom) indicates which setting is currently selected.
You can select different settings by pressing the 🟦PREV button (previous) and 🟦NEXT button (next). By pressing these buttons you cycle through the settings of controller A and controller B.
Note
When you press the 🟦NEXT button at the last setting of controller B you will go to the first setting of controller A.
When you press the 🟦PREV button at the first setting of controller A you will go to the last setting of controller B.
You can change the value of the selected setting by pressing the ⬛DEC button (decrease) and ⬛INC button (increase).
Tip
If you keep either ⬛DEC or ⬛INC button pressed it will scroll faster through the values.
Note
When you return to Setup Mode after visiting Play mode you will return to the most recently edited setting.
Each controller is configured by 9 settings arranged in 3 screens of 3 settings each. The third screen has settings that are dependent of the chosen type of operation on screen 1.
- ACTV: Active
- ON = Active
- OFF = Inactive
- TYPE: Type of operation
- CC = Send MIDI CC changes
- NOT = Send MIDI Notes
- CHD = Send MIDI Chords
- PB = Send MIDI Pitchbend
- CHNL: MIDI Channel
- 1-16 = MIDI Channel number
- LDST: Low Distance
- 5-80 = Low end of the operating range in cm (in steps of 5)
- HDST: High Distance
- 5-80 = High end of the operating range in cm (in steps of 5)
- POLR: Polarity
- POS = Positive mapping
- NEG = Negative mapping
Note
The HDST must be higher than the LDST. This is enforced when setting the values.
The following image illustrates the effect of using positive and negative polarity.
- CNTR: Controller number
- 0-127 = MIDI CC number
- LVAL: Low Value
- 0-127 = Lowest value generated
- HVAL: High Value
- 0-127 = Highest value generated
Note
The HVAL must be higher than the LVAL. This is enforced when setting the values.
Tip
The use of MIDI CC is synthesizer specific. So the manufacturer of the synthesizer determines which CC value controls what parameter of the sound engine. So take a look at the manual of the synthesizer for a mapping of the CC values. Most likely there will be an appendix with a name of MIDI controller list (or equivalent).
The following image illustrates controlling the filter cutoff (controller A) and filter resonance (controller B) on a Novation KS-rack synthesizer module.
- SCAL: Musicial note scale
- CHR = Chromatic scale
- MAJ = Major scale
- MIN = Minor scale
- MMI = Melodic Minor scale
- HMI = Harmonic Minor scale
- WHL = Whole Tone scale
- MAB = Major Blues scale
- MIB = Minor Blues scale
- MA5 = Major Pentatonic scale
- MI5 = Minor Pentatonic scale
- 8WH = Octatonic Whole Half scale
- 8HW = Octatonic Half Whole scale
- ROOT: Root note
- C0-B8 - Root note for the scale
- RANG: Number of scale notes to be played
The following image shows the notes of the different scales for the root note C.
- PROG: Musical chord progression
- MAJ = Major chord progression
- MIN = Minor chord progression
- MAB = Major Blues 7th chord progession
- MIB = Minor Blues 7th chord progression
- POP = Pop chord progression
- JAZ = Jazz chord progression (undocumented)
- MOD = Modal chord progression (undocumented)
- GSP = Gospel chord progression (undocumented)
- PBL = Pachelbel chord progression (undocumented)
- ROOT: Root note
- C0-B8 - Root note for the chord progression
- RANG: Number of progression chords to be played
The following image shows the chords of the different progressions for the root note C.
- TYPE: Pitchbend type
- UP = Bend the pitch up
- DWN = Bend the pitch down
- U&D = Bend the pitch up and down
- NTRL: Neutral zone size
- SML = Small
- MED = Medium
- LRG = Large
- PBFX: Pitchbend effects
- FLW = Flowing pitch bend
- STP = Stepping pitch bend
The following image shows the effect of using the pitchbend types and neutral zone sizes.
Note
The neutral zone is comparable to a pitchbend wheel in its neutral/center position. The pitchbend maximum is comparable to a pitchbend wheel completely up or down. As with the pitchbend wheel this doesn't say anything about the actual pitchbend in semitones. The semitone range of the pitchbend is determined by the setup of the synthesizer. On most synthesizers it is even possible to setup individual semitone ranges for pitchbend up and pitchbend down.