Rotary Trinkey

A USB stick with a rotary encoder you solder on yourself, a push switch under the knob, a capacitive touch pad and one NeoPixel. George's CircuitPython firmware makes it a class-compliant MIDI device: no driver, no library on either end. The knob sends two things at once, an absolute position and a relative click, so a sketch can pick whichever is easier.


Maker	Adafruit, with George's firmware
USB name	"Rotary Trinkey M0"
Ports	1 in, 1 out
Sends	CC 2 absolute and CC 3 relative for the knob, note 61 for the press, note 62 for the touch pad, channel 1.
Receives	Any note on. The pixel takes that note's colour for a second.
Buy	adafruit.com/product/4964
Firmware	firmware/trinkey-midi, CircuitPython

What it sends

Control	Message	Numbers	Notes
Knob, absolute	CC	CC 2, 0 to 127	The position. Sent on every click, and once at startup.
Knob, relative	CC	CC 3	1 is one click clockwise, 127 one click counter-clockwise. Two's complement, so 2 is two clicks.
Knob press	Note on, note off	Note 61, velocity 127	Down and up.
Touch pad	Note on, note off	Note 62, velocity 127	On when touched, off on release.
USB name		"Rotary Trinkey M0"	The drive, when it mounts, is `ROTARYPY`.

What it receives

Message	Effect
Any note on	The pixel takes a colour from the note number for one second. `m.noteOn(1, 61, 127)` from a sketch.

Everything is on channel 1. The board sends one CC 2 with the knob's position at startup. Whatever the switch reads at power-up counts as released, so don't hold it while plugging in. Flashing and the pin names are in the trinkey-midi README.

Start here

There is no dedicated starter yet. The generic one draws every note and CC it hears, so turn the knob and watch CC 2 and CC 3. Then use the helper below.

p5.js
Python Mode
Java

Click inside the sketch to connect MIDI. No device? The keys named in the code stand in.

Open full page

This is the generic starter. It draws every note and CC the knob sends. Code: starters/p5/anything-else/sketch.js. Paste it into the p5.js web editor with the helper script tag, or download the folder and double-click index.html.

sketch.js
// AnyMidi starter: the Explorer's raw log as a sketch. A connection line, a device picker, the last 12 messages
// (time, device, channel, type, number, value, raw bytes), then note circles and CC bars underneath to play with.
// Click once to connect MIDI. No device: letters are notes, drag the mouse for a knob.
let m, picker, known = "", log = [];
const pop = new Array(128).fill(0), knob = new Array(128).fill(0);
const TYPES = { 0x80: "noteOff", 0x90: "noteOn", 0xa0: "polyTouch", 0xb0: "cc", 0xc0: "program", 0xd0: "aftertouch", 0xe0: "pitchBend" };

function setup() {
  const cnv = createCanvas(900, 560);
  textFont("monospace"); textSize(12); noStroke();
  picker = createSelect(); picker.option("All inputs");         // the device picker, above the canvas
  cnv.elt.parentNode.insertBefore(picker.elt, cnv.elt);
  m = new AnyMidi();                                             // no name: every input
  m.connectOnClick(() => {});                                    // the connection line below replaces the helper's hint
}

const wanted = (device) => picker.value() === "All inputs" || device === picker.value();
function logMsg(status, d1, d2, device, value) {                 // one line per message, newest last
  if (!wanted(device)) return;
  const type = TYPES[status & 0xf0] || "status " + status, ch = status < 0xf0 ? "ch" + String((status & 0x0f) + 1).padStart(2) : "    ";
  log.push(`${(millis() / 1000).toFixed(2).padStart(7)}  ${device.slice(0, 18).padEnd(18)}  ${ch}  ${type.padEnd(10)} ${String(d1).padStart(3)} ${String(value).padStart(5)}   [${status}, ${d1}, ${d2}]`);
  if (log.length > 12) log.shift();
}
function raw(status, d1, d2, device) {                           // the bytes as received; rebuilt for the keyboard stand-in
  return device === "keyboard" || !m.last ? [status, d1, d2] : [m.last.status, m.last.data1, m.last.data2];
}

function draw() {
  if (m.core.access && !m.core.access.onstatechange) m.core.access.onstatechange = () => m.connect();   // devices come and go: reopen
  const inputs = m.devices();                                    // repopulate the picker when the list changes
  if (inputs.join("|") !== known) {
    known = inputs.join("|"); const keep = picker.value(); picker.elt.innerHTML = "";
    picker.option("All inputs"); for (const n of inputs) picker.option(n); if (inputs.includes(keep)) picker.selected(keep);
  }
  background(15); fill(200);
  text(m.connected() ? m.status : m.status.startsWith("no MIDI") ? "no MIDI inputs found" : m.status, 16, 22);   // the connection line
  for (let i = 0; i < log.length; i++) text(log[i], 16, 50 + i * 16);
  for (let n = 0; n < 128; n++) {                                // the playground: change this part
    const x = map(n, 0, 127, 10, width - 10);
    fill(90, 200, 255); rect(x - 2, height - 10, 4, -knob[n] * 1.5);          // change this: bars for CC values 0..127
    if (pop[n] > 0) { fill(255, 120, 80, pop[n] * 2); circle(x, 370, pop[n]); pop[n] -= 2; }   // change this: what a note looks like
  }
}

// The helper calls these for every message, with the device name last. Channel is 1..16.
function noteOn(ch, n, v, dev = "keyboard") { logMsg(...raw(0x90 | (ch - 1), n, v, dev), dev, v); if (wanted(dev)) pop[n] = 40 + v; }       // change this
function noteOff(ch, n, v, dev = "keyboard") { logMsg(...raw(0x80 | (ch - 1), n, v, dev), dev, v); }
function controlChange(ch, cc, val, dev = "keyboard") { logMsg(...raw(0xb0 | (ch - 1), cc, val, dev), dev, val); if (wanted(dev)) knob[cc] = val; }   // change this
function pitchBend(ch, value, dev = "keyboard") { const v = value + 8192; logMsg(...raw(0xe0 | (ch - 1), v & 0x7f, v >> 7, dev), dev, value); }
function midiMessage(status, d1, d2, dev = "keyboard") { logMsg(status, d1, d2, dev, d2); }   // everything else: program, aftertouch, clock...

// Stand-ins, so the sketch does something with no device.
function keyPressed() { if (key.length === 1) noteOn(1, 48 + key.charCodeAt(0) % 36, 100); }
function mouseDragged() { controlChange(1, 1 + floor(mouseY * 8 / height), floor(map(mouseX, 0, width, 0, 127))); }

Open starters/python/anymidi_starter/anymidi_starter.pyde. The generic starter. It runs as is. For the helper, copy trinkeys.py from midi-helpers/python/ next to it.

anymidi_starter.pyde
# AnyMidi starter: the Explorer's raw log as a sketch. A connection line, a device list to click, the last 12
# messages (time, device, channel, type, number, value, raw bytes), then note circles and CC bars to play with.
# No device: letters are notes, drag the mouse for a knob. Under 60 lines; edit the lines marked "change this".
from __future__ import division, print_function
from anymidi import AnyMidi

m = None
S = {"picked": "All inputs"}
log = []
pop, knob = [0] * 128, [0] * 128   # per note: a shrinking circle; per CC: the last value
TYPES = {0x80: "noteOff", 0x90: "noteOn", 0xA0: "polyTouch", 0xB0: "cc", 0xC0: "program", 0xD0: "aftertouch", 0xE0: "pitchBend"}

def setup():
    global m
    size(900, 560); textFont(createFont("Monospaced", 12)); noStroke()
    m = AnyMidi(this)    # no name: every input
    m.connect()          # console: every port, and which ones opened
def wanted(device): return S["picked"] == "All inputs" or S["picked"] == device
def choices(): return ["All inputs"] + m.devices()

def log_msg(status, d1, d2, device, value):    # one line per message, newest last
    if not wanted(device): return
    if device != "keyboard" and m.last is not None: status, d1, d2 = m.last.status, m.last.data1, m.last.data2   # the bytes as received
    ch = "ch%2d" % ((status & 0x0F) + 1) if status < 0xF0 else "    "
    log.append("%7.2f  %-18.18s  %s  %-10s %3d %5d   [%d, %d, %d]" % (millis() / 1000.0, device, ch, TYPES.get(status & 0xF0, "status %d" % status), d1, value, status, d1, d2))
    if len(log) > 12: del log[0]
def draw():
    m.update()           # the callbacks fire here
    background(15); fill(200)
    text(m.status if m.connected() else "no MIDI inputs found", 16, 22)   # the connection line
    x = 16                                                       # the device list: click one
    for name in choices():
        fill(color(255, 200, 60) if name == S["picked"] else 130); text(name, x, 42); x += textWidth(name) + 24
    fill(200)
    for i, line in enumerate(log): text(line, 16, 70 + i * 16)
    for n in range(128):                                         # the playground: change this part
        px = 10 + n * (width - 20) / 127
        fill(90, 200, 255); rect(px - 2, height - 10, 4, -knob[n] * 1.5)          # change this: bars for CC values 0..127
        if pop[n] > 0:
            fill(255, 120, 80, pop[n] * 2); circle(px, 370, pop[n]); pop[n] -= 2  # change this: what a note looks like

# The helper calls these for every message, device name last. Channel is 1..16.
def note_on(ch, n, v, dev="keyboard"):
    log_msg(0x90 | (ch - 1), n, v, dev, v)
    if wanted(dev): pop[n] = 40 + v                              # change this
def note_off(ch, n, v, dev="keyboard"): log_msg(0x80 | (ch - 1), n, v, dev, v)
def control_change(ch, cc, val, dev="keyboard"):
    log_msg(0xB0 | (ch - 1), cc, val, dev, val)
    if wanted(dev): knob[cc] = val                               # change this
def pitch_bend(ch, value, dev="keyboard"): v = value + 8192; log_msg(0xE0 | (ch - 1), v & 0x7F, v >> 7, dev, value)
def midi_message(status, d1, d2, dev="keyboard"): log_msg(status, d1, d2, dev, d2)   # everything else
# Stand-ins, so the sketch does something with no device.
def keyPressed():
    if key != CODED: note_on(1, 48 + ord(str(key)[0]) % 36, 100)
def mousePressed():
    x = 16
    for name in choices():
        if 30 < mouseY < 48 and x <= mouseX < x + textWidth(name): S["picked"] = name
        x += textWidth(name) + 24
def mouseDragged(): control_change(1, 1 + mouseY * 8 // height, mouseX * 127 // width)
def stop(): m.close()

Open starters/java/AnyMidiStarter/AnyMidiStarter.pde. The generic starter. It runs as is. For the helper, copy Trinkeys.pde from midi-helpers/java/ into the sketch folder.

AnyMidiStarter.pde
// AnyMidi starter: the Explorer's raw log as a sketch. A connection line, a device list to click, the last 12
// messages (time, device, channel, type, number, value, raw bytes), then note circles and CC bars to play with.
// No device: letters are notes, drag the mouse for a knob. Under 60 lines; edit the lines marked "change this".
AnyMidi m;
String picked = "All inputs";
ArrayList<String> log = new ArrayList<String>();
float[] pop = new float[128];      // one per note number, shrinks every frame
int[] knob = new int[128];         // last value of each control change number

void setup() {
  size(900, 560);
  textFont(createFont("Monospaced", 12));
  noStroke();
  m = new AnyMidi(this);           // no name: every input
  m.connect();                     // console: every port, and which ones opened
}

boolean wanted(String device) { return picked.equals("All inputs") || picked.equals(device); }
String[] choices() { return concat(new String[] { "All inputs" }, m.devices()); }
String typeName(int t) { return t == 0x80 ? "noteOff" : t == 0x90 ? "noteOn" : t == 0xA0 ? "polyTouch" : t == 0xB0 ? "cc" : t == 0xC0 ? "program" : t == 0xD0 ? "aftertouch" : t == 0xE0 ? "pitchBend" : "status " + t; }

void logMsg(int status, int d1, int d2, String device, int value) {   // one line per message, newest last
  if (!wanted(device)) return;
  if (!device.equals("keyboard") && m.last != null) { status = m.last.status; d1 = m.last.data1; d2 = m.last.data2; }   // the bytes as received, not rebuilt
  String ch = status < 0xF0 ? String.format("ch%2d", (status & 0x0F) + 1) : "    ";
  log.add(String.format("%7.2f  %-18.18s  %s  %-10s %3d %5d   [%d, %d, %d]", millis() / 1000.0, device, ch, typeName(status & 0xF0), d1, value, status, d1, d2));
  if (log.size() > 12) log.remove(0);
}

void draw() {
  background(15);
  fill(200);
  text(m.connected() ? m.status() : "no MIDI inputs found", 16, 22);   // the connection line
  float x = 16;                                                        // the device list: click one
  for (String name : choices()) { fill(name.equals(picked) ? color(255, 200, 60) : 130); text(name, x, 42); x += textWidth(name) + 24; }
  fill(200);
  for (int i = 0; i < log.size(); i++) text(log.get(i), 16, 70 + i * 16);
  for (int n = 0; n < 128; n++) {                                      // the playground: change this part
    float px = map(n, 0, 127, 10, width - 10);
    fill(90, 200, 255); rect(px - 2, height - 10, 4, -knob[n] * 1.5);              // change this: bars for CC values 0..127
    if (pop[n] > 0) { fill(255, 120, 80, pop[n] * 2); circle(px, 370, pop[n]); pop[n] -= 2; }   // change this: what a note looks like
  }
}

// The helper calls these for every message, with the device name last. Channel is 1..16.
void noteOn(int ch, int n, int v, String dev) { logMsg(0x90 | (ch - 1), n, v, dev, v); if (wanted(dev)) pop[n] = 40 + v; }        // change this
void noteOff(int ch, int n, int v, String dev) { logMsg(0x80 | (ch - 1), n, v, dev, v); }
void controlChange(int ch, int cc, int val, String dev) { logMsg(0xB0 | (ch - 1), cc, val, dev, val); if (wanted(dev)) knob[cc] = val; }   // change this
void pitchBend(int ch, int value, String dev) { int v = value + 8192; logMsg(0xE0 | (ch - 1), v & 0x7F, v >> 7, dev, value); }
void midiMessage(int status, int d1, int d2, String dev) { logMsg(status, d1, d2, dev, d2); }   // everything else: program, aftertouch, clock...

// Stand-ins, so the sketch does something with no device.
void keyPressed() { if (key != CODED) noteOn(1, 48 + key % 36, 100, "keyboard"); }
void mousePressed() { float x = 16; for (String name : choices()) { if (mouseY > 30 && mouseY < 48 && mouseX >= x && mouseX < x + textWidth(name)) picked = name; x += textWidth(name) + 24; } }
void mouseDragged() { controlChange(1, 1 + mouseY * 8 / height, int(map(mouseX, 0, width, 0, 127)), "keyboard"); }

The helper


`new RotaryTrinkey(this)`	Connects to the first device whose name contains "Rotary Trinkey". `(this, "name")` to change it.
`knob.value`, `knob.raw`	Absolute position, 0 to 1 and 0 to 127.
`knob.delta`	Clicks since the last frame. Positive is clockwise, 0 when still. A fast spin reads as 2 or 3.
`knob.pressed`, `knob.justPressed()`, `knob.justReleased()`	The push switch.
`knob.touched`, `knob.justTouched()`, `knob.justTouchReleased()`	The touch pad.
`knob.pixel(note)`	Sends a note on and off to the board. The pixel shows that note's colour for a second.
`void knobTurned(int delta)`, `void knobPressed()`, `void knobReleased()`, `void touchPressed()`, `void touchReleased()`	Define any in your sketch and the helper calls it.

Stand-ins with nothing plugged in: LEFT and RIGHT are one click each, ENTER presses, T touches.

From the helpers' README

Thin helpers over the CircuitPython firmware in trinkeys/ (its README covers flashing). One file holds both classes.

SlideTrinkey slide = new SlideTrinkey(this);     // matches "Slide Trinkey"; (this, "name") to change it
RotaryTrinkey knob = new RotaryTrinkey(this);    // matches "Rotary Trinkey"
slide.value;                                     // 0..1, 0 = left, 1 = right
slide.raw;                                       // the CC value 0..127, -1 until the first message (the board sends one at startup)
slide.touched; slide.justTouched(); slide.justReleased();
slide.pixel(note);                               // Note On + Note Off to the board: pixel colour from the note number, one second
knob.value; knob.raw;                            // absolute position 0..1 / 0..127
knob.delta;                                      // clicks since the last frame: + clockwise, - counter-clockwise, 0 when still
knob.pressed; knob.justPressed(); knob.justReleased();
knob.touched; knob.justTouched(); knob.justTouchReleased(); knob.pixel(note);

Callbacks: sliderChanged(float value), knobTurned(int delta), knobPressed(), knobReleased(), touchPressed(), touchReleased(). Both boards use the touch names; with both plugged in, read slide.touched / knob.touched. Stand-ins: Slide = LEFT/RIGHT move, T touches; Rotary = LEFT/RIGHT one click per press, ENTER presses, T touches.

Message map (channel 1, from trinkeys/README.md):

Board	Sends	Listens
Slide Trinkey M0	CC 1 slider 0..127 (0 left, 127 right); note 60 touch pad (Note On / Off)	any Note On: pixel colour from the note number, one second
Rotary Trinkey M0	CC 2 absolute 0..127; CC 3 relative, 1 = one click clockwise, 127 = one click counter-clockwise (two's complement, so 2 = two clicks); note 61 knob press; note 62 touch pad	same

delta is the sum of the relative clicks since the previous frame, so a fast spin reads as 2 or 3.

Python: SlideTrinkey(this), RotaryTrinkey(this), slide.value, slide.raw, slide.touched, slide.just_touched(), slide.just_released(), slide.pixel(note), knob.value, knob.raw, knob.delta, knob.pressed, knob.just_pressed(), knob.just_released(), knob.touched, knob.just_touched(), knob.pixel(note); callbacks slider_changed(value), knob_turned(delta), knob_pressed(), knob_released(), touch_pressed(), touch_released(); module-level relative(v). p5: new SlideTrinkey(), new RotaryTrinkey() with the Java names; RotaryTrinkey.relative(v).

Try first

A dial on screen that follows value. Then one that only ever moves by delta, so it never jumps.
Scroll through a list of colours, press to pick one, send it back to the pixel.
A metronome whose tempo is the knob.

Without the helper

Two CCs and two notes, so the raw path is HelloMidi: it opens every input and prints every message. Read the three bytes, no helpers first.

Java mode: starters/raw/java/HelloMidi/
Python Mode: starters/raw/python/hello_midi/
p5.js: starters/raw/p5/hello-midi/, or its sketch.js

What it sends​

What it receives​

Start here​

The helper​

From the helpers' README​

Try first​

Without the helper​