Create cpx-expressive-midi-controller.py
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Mike Barela
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### cpx-expressive-midi-controller v1.2
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### CircuitPython (on CPX) MIDI controller using the seven touch pads
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### and accelerometer for modulation (cc1) and pitch bend
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### Left button adjusts octave (switch left) or semitone (switch right)
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### Right button adjusts scale, major or chromatic
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### Switch right also disables pitch bend and modulation
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### Tested with CPX and CircuitPython and 4.0.0-beta.5
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### Needs recent adafruit_midi module
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### copy this file to CPX as code.py
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### MIT License
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### Copyright (c) 2019 Kevin J. Walters
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### Permission is hereby granted, free of charge, to any person obtaining a copy
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### of this software and associated documentation files (the "Software"), to deal
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### in the Software without restriction, including without limitation the rights
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### to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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### copies of the Software, and to permit persons to whom the Software is
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### furnished to do so, subject to the following conditions:
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### The above copyright notice and this permission notice shall be included in all
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### copies or substantial portions of the Software.
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### THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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### IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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### FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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### AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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### LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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### OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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### SOFTWARE.
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import time
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import digitalio
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import touchio
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import busio
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import board
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import usb_midi
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import neopixel
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import adafruit_lis3dh
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import adafruit_midi
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from adafruit_midi.note_on import NoteOn
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from adafruit_midi.control_change import ControlChange
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from adafruit_midi.pitch_bend import PitchBend
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# MIDI defines middle C as 60 and modulation wheel is cc 1 by convention
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midi_note_C4 = 60
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midi_cc_modwheel = const(1)
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# 0x19 is the i2c address of the onboard accelerometer
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acc_i2c = busio.I2C(board.ACCELEROMETER_SCL, board.ACCELEROMETER_SDA)
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acc_int1 = digitalio.DigitalInOut(board.ACCELEROMETER_INTERRUPT)
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acc = adafruit_lis3dh.LIS3DH_I2C(acc_i2c, address=0x19, int1=acc_int1)
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acc.range = adafruit_lis3dh.RANGE_2_G
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acc.data_rate = adafruit_lis3dh.DATARATE_10_HZ
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# brightness 1.0 saves memory by removing need for a second buffer
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# 10 is number of NeoPixels on CPX
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numpixels = const(10)
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pixels = neopixel.NeoPixel(board.NEOPIXEL, numpixels, brightness=1.0)
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# Turn NeoPixel on to represent a note using RGB x 10
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# to represent 30 notes - doesn't do anything with pitch bend
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def noteLED(pix, pnote, pvel):
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note30 = (pnote - midi_note_C4) % (3 * numpixels)
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pos = note30 % numpixels
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r, g, b = pix[pos]
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if pvel == 0:
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brightness = 0
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else:
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# max brightness will be 32
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brightness = round(pvel / 127 * 30 + 2)
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# Pick R/G/B based on range within the 30 notes
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if note30 < 10:
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r = brightness
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elif note30 < 20:
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g = brightness
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else:
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b = brightness
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pix[pos] = (r, g, b)
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# white pulse used to indicate octave changes
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flashbrightness = 20
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def flashLED(pix, position):
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pos = position % numpixels
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t1 = time.monotonic()
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oldcolour = pix[pos]
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while time.monotonic() - t1 < 0.25:
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for i in range(0, flashbrightness, 2):
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pix[pos] = (i, i, i)
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for i in range(flashbrightness, 0, -2):
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pix[pos] = (i, i, i)
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pix[pos] = oldcolour
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midi_channel = 1
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midi = adafruit_midi.MIDI(midi_out=usb_midi.ports[1],
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out_channel=midi_channel-1)
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# CPX counter-clockwise order of touch capable pads (i.e. not A0)
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pads = [board.A4,
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board.A5,
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board.A6,
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board.A7,
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board.A1,
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board.A2,
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board.A3]
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# The touch pads calibrate themselves as they are created, just once here
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touchpads = [touchio.TouchIn(pad) for pad in pads]
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del pads # done with that
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pb_midpoint = 8192
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pitch_bend_value = pb_midpoint # mid point - no bend
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min_pb_change = 250
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mod_wheel = 0
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min_mod_change = 5
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# button A is on left (usb at top)
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button_left = digitalio.DigitalInOut(board.BUTTON_A)
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button_left.switch_to_input(pull=digitalio.Pull.DOWN)
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button_right = digitalio.DigitalInOut(board.BUTTON_B)
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button_right.switch_to_input(pull=digitalio.Pull.DOWN)
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switch_left = digitalio.DigitalInOut(board.SLIDE_SWITCH)
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switch_left.switch_to_input(pull=digitalio.Pull.UP)
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# some example scales in semitones
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scale_st = {"major": [0, 2, 4, 5, 7, 9, 11],
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"chromatic": [0, 1, 2, 3, 4, 5, 6]}
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scales = ["major", "chromatic"]
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scale_idx = 0
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base_note = midi_note_C4 # C4 middle C
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def make_scale(scale_name):
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return [semitone_offset + base_note
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for semitone_offset in scale_st[scale_name]]
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midi_notes = make_scale(scales[scale_idx])
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keydown = [False] * 7
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velocity = 127
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min_octave = -3
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max_octave = +3
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octave = 0
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min_semitone = -11
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max_semitone = +11
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semitone = 0
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# 1/10 = 10 Hz - review data_rate setting if this is changed
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acc_read_t = time.monotonic()
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acc_read_period = 1/10
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# For accelerometer do nothing between 0 and 1.3 (ms-2)
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acc_nullzone = 1.3
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acc_range = 4.0
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# Convert an accelerometer reading
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# from min_msm2 to min_msm2+range to an int from 0 to value_range
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# or return 0 or value_range outside those values
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# The conversion is applied "symmetrically" to negative numbers
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def scale_acc(acc_msm2, min_msm2, range_msm2, value_range):
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if acc_msm2 >= 0.0:
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sign_a_m = 1
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magn_acc_msm2 = acc_msm2
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else:
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sign_a_m = -1
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magn_acc_msm2 = abs(acc_msm2)
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adj_msm2 = magn_acc_msm2 - min_msm2
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# deal with out of bounds values else scale value
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# pylint: disable=no-else-return
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if adj_msm2 <= 0:
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return 0
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elif adj_msm2 >= range_msm2:
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return sign_a_m * value_range
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else:
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return sign_a_m * round(adj_msm2 / range_msm2 * value_range)
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# Scan each pad and look for changes by comparing
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# with keystate stored in keydown boolean list
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# and send note on/off messages accordingly
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# Send pitch bend and mod wheel cc based on tilt from accelerometer
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# Change octave and semitone based on buttons
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while True:
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for idx, touchpad in enumerate(touchpads):
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if touchpad.value != keydown[idx]:
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keydown[idx] = touchpad.value
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# 12 semitones in an octave
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note = midi_notes[idx] + octave * 12 + semitone
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if keydown[idx]:
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midi.send(NoteOn(note, velocity))
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noteLED(pixels, note, velocity)
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else:
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midi.send(NoteOn(note, 0)) # Using note on 0 for off
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noteLED(pixels, note, 0)
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# Perform rate limited checks on the accelerometer
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# if switch is to left
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now_t = time.monotonic()
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if switch_left.value and now_t - acc_read_t > acc_read_period:
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acc_read_t = time.monotonic()
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ax, ay, az = acc.acceleration
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# scale from 0 to 127 (maximum cc 7bit value)
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new_mod_wheel = abs(scale_acc(ay, acc_nullzone, acc_range, 127))
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if (abs(new_mod_wheel - mod_wheel) > min_mod_change
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or (new_mod_wheel == 0 and mod_wheel != 0)):
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midi.send(ControlChange(midi_cc_modwheel, new_mod_wheel))
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mod_wheel = new_mod_wheel
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# scale from 0 to +/- 8191 (almost maximum signed 14bit values)
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new_pitch_bend_value = (pb_midpoint
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- scale_acc(ax, acc_nullzone, acc_range,
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pb_midpoint - 1))
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if (abs(new_pitch_bend_value - pitch_bend_value) > min_pb_change
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or (new_pitch_bend_value == pb_midpoint
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and pitch_bend_value != pb_midpoint)):
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midi.send(PitchBend(new_pitch_bend_value))
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pitch_bend_value = new_pitch_bend_value
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# left button increase octave / semitones shift based on switch
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# does not currently clear playing notes (buglet)
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if button_left.value:
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if switch_left.value:
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octave += 1
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if octave > max_octave:
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octave = min_octave
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flashLED(pixels, octave)
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else:
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semitone += 1
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if semitone > max_semitone:
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semitone = min_semitone
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# semitone range is more than number of pixels!
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flashLED(pixels, semitone)
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while button_left.value:
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pass # wait for button up
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# right button cycles through scales
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if button_right.value:
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scale_idx += 1
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if scale_idx >= len(scales):
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scale_idx = 0
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flashLED(pixels, scale_idx)
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midi_notes = make_scale(scales[scale_idx])
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while button_right.value:
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pass # wait for button up
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