459 lines
No EOL
16 KiB
Python
459 lines
No EOL
16 KiB
Python
# SPDX-FileCopyrightText: 2021 Sandy Macdonald
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#
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# SPDX-License-Identifier: MIT
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# A MIDI step sequencer, with four tracks and eight steps per track.
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# The eight steps are on the top two rows of keys. Steps can be toggled on by
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# tapping a step's key. Active steps are indicated with a brighter LED, and the
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# currently playing step in the sequence is shown with a moving LED across the
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# eight steps.
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# Each track is colour-coded: track 1 is orange, track 2 teal, track 3 is pink,
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# and track 4 is green. Tracks can be selected by pressing and holding the
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# bottom left orange track select key and then tapping one of the four track
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# keys on the row above.
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# The sequencer is started and stopped by tapping the bottom right key, which is
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# red when the sequencer is stopped, and green when it is playing.
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# The sequencer can be cleared by holding the track selector key (orange, bottom
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# left) and then holding the start/stop key (red/green, bottom right).
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# Tempo can be increased or decreased by holding the tempo selector key (teal,
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# second from left, on the bottom row) and then tapping teal key on the row
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# above to shift tempo down, or the pink key to shift it up. Tempo is increased/
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# decreased by 5 BPM on each press.
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# You'll need to connect Keybow 2040 to a computer running a DAW like Ableton,
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# or other software synth, or to a hardware synth that accepts USB MIDI.
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# Currently, all of the notes are C3 with a velocity of 127.
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# Tracks' notes are sent on MIDI channels 1-4.
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# Drop the keybow2040.py file into your `lib` folder on your `CIRCUITPY` drive,
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# and then save this code in the `code.py` file
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# NOTE! Requires the adafruit_midi CircuitPython library also!
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import time
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import board
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from keybow2040 import Keybow2040
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import usb_midi
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import adafruit_midi
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from adafruit_midi.note_off import NoteOff
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from adafruit_midi.note_on import NoteOn
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# These are the key numbers that represent each step in a track (the top two
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# rows of four keys)
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TRACK_KEYS = [3, 7, 11, 15, 2, 6, 10, 14]
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# The colours for the LEDs on each track: orange, teal, pink, green
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TRACK_COLOURS = [
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(255, 255, 0),
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(0, 255, 175),
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(255, 0, 255),
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(0, 255, 0)
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]
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# The MIDI channels for each track in turn: 1, 2, 3, 4
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MIDI_CHANNELS = [0, 1, 2, 3]
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# The bottom left key, orange. When pressed, it brings up the track selector
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# keys, the four keys on the row above it.
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TRACK_SELECTOR = 0
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TRACK_SELECTOR_KEYS = [1, 5, 9, 13]
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TRACK_SELECTOR_COLOUR = (255, 255, 0)
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# The bottom right key. When pressed, it toggles the sequencer on or off. Green
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# indicates that it is currently playing, red that it is stopped.
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START_STOP = 12
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START_COLOUR = (0, 255, 0)
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STOP_COLOUR = (255, 0, 0)
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# The key second from left on the bottom row, teal. When pressed, it brings up
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# the tempo down/up buttons on the row above it. The left teal key shifts the
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# tempo down, the right pink key shifts the tempo up.
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TEMPO_SELECTOR = 4
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TEMPO_SELECTOR_COLOUR = (0, 255, 175)
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TEMPO_DOWN = 5
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TEMPO_DOWN_COLOUR = (0, 255, 175)
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TEMPO_UP = 9
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TEMPO_UP_COLOUR = (255, 0, 255)
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# The default starting BPM.
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BPM = 85
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# Dictates the time after which a key is "held".
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KEY_HOLD_TIME = 0.25
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# LED brightness settings for the track steps.
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PLAY_BRIGHTNESS = 1.0
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ACTIVE_BRIGHTNESS = 0.2
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STEP_BRIGHTNESS = 0.05
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class Sequencer(Keybow2040):
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"""
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Represents the sequencer, with a set of Track instances, which in turn have
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a set of Step instances. This class is a subclass of the Keybow2040 class,
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so it inherits all of its methods and key methods.
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:param i2c: the I2C bus for Keybow 2040
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"""
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def __init__(self, *args, **kwargs):
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super(Sequencer, self).__init__(*args, **kwargs)
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# Holds the list of MIDI channels for the tracks.
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self.midi_channels = []
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# Set the MIDI channels up.
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for channel in MIDI_CHANNELS:
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midi = adafruit_midi.MIDI(midi_out=usb_midi.ports[1], out_channel=channel)
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self.midi_channels.append(midi)
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# Holds the list of tracks, a set of Track instances.
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self.tracks = []
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# Set the tracks up.
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for i in range(4):
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track = Track(self, i, i, TRACK_COLOURS[i])
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self.tracks.append(track)
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# Speed attributes.
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self.bpm = BPM
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self.tempo_selector = self.keys[TEMPO_SELECTOR]
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self.tempo_selector.set_led(*TEMPO_SELECTOR_COLOUR)
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self.tempo_select_active = False
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self.tempo_down = self.keys[TEMPO_DOWN]
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self.tempo_up = self.keys[TEMPO_UP]
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# Step related stuff
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self.num_steps = 8
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self.this_step_num = 0
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self.last_step_num = 0
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# Is the sequencer running?
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self.running = False
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# Step time assumes the BPM is based on quarter notes.
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self.step_time = 60.0 / self.bpm / (self.num_steps / 2)
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self.last_step_time = time.monotonic()
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# Set the default starting track to track 0
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self.current_track = 0
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# The start stop key.
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self.start_stop = self.keys[START_STOP]
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self.start_stop.set_led(*STOP_COLOUR)
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# The track selector key.
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self.track_selector = self.keys[TRACK_SELECTOR]
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self.track_selector.set_led(*TRACK_SELECTOR_COLOUR)
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self.track_selector_active = False
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# These keys select and change the current track.
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self.track_select_keys = []
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for i in range(len(TRACK_SELECTOR_KEYS)):
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track_key = self.keys[TRACK_SELECTOR_KEYS[i]]
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track_key.rgb = TRACK_COLOURS[i]
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self.track_select_keys.append(track_key)
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# Set the key hold time for all the keys. A little shorter than the
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# default for Keybow. Makes controlling the sequencer a bit more fluid.
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for key in self.keys:
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key.hold_time = KEY_HOLD_TIME
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# Attach step_select function to keys in track steps. If pressed it
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# toggles the state of the step.
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for i in range(len(TRACK_KEYS)):
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key = self.keys[TRACK_KEYS[i]]
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@self.on_press(key)
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def step_select(key):
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step_num = TRACK_KEYS.index(key.number)
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step = self.tracks[self.current_track].steps[step_num]
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step.toggle()
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# Attach hold function to track selector key that sets it active and
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# lights the track select keys.
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@self.on_hold(self.track_selector)
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def track_selector_hold(key):
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self.track_selector_active = True
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for key in self.track_select_keys:
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key.led_on()
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# Attach release function to track selector key that sets it inactive
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# and turns track select LEDs off.
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@self.on_release(self.track_selector)
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def track_selector_release(key):
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self.track_selector_active = False
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for key in self.track_select_keys:
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key.led_off()
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# Track 0 select.
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@self.on_press(self.track_select_keys[0])
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def track_select_0_press(key):
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if self.track_selector_active:
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self.current_track = 0
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# Special case to handle track 1 select and tempo down.
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# Pressing the tempo down key shifts the tempo down by
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# 5 bpm each time it is pressed, with a lower limit of 5 BPM.
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@self.on_press(self.track_select_keys[1])
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def track_select_1_press(key):
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if self.track_selector_active:
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self.current_track = 1
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else:
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if self.tempo_select_active:
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if self.bpm > 5:
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self.bpm -= 5
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# Special case to handle track 2 select and tempo up.
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# Pressing the tempo up key shifts the tempo up by
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# 5 bpm each time it is pressed, with an upper limit of 200 BPM.
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@self.on_press(self.track_select_keys[2])
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def track_select_2_press(key):
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if self.track_selector_active:
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self.current_track = 2
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else:
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if self.tempo_select_active:
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if self.bpm < 200:
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self.bpm += 5
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# Track 3 select.
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@self.on_press(self.track_select_keys[3])
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def track_select_3_press(key):
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if self.track_selector_active:
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self.current_track = 3
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# Attach press function to start/stop key that toggles whether the
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# sequencer is running and toggles its colour between green (running)
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# and red (not running).
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@self.on_press(self.start_stop)
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def start_stop_toggle(key):
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if not self.track_selector_active:
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if self.running:
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self.running = False
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key.set_led(*STOP_COLOUR)
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else:
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self.running = True
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key.set_led(*START_COLOUR)
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# Attach hold function, so that when the track selector key is held and
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# the start/stop key is also held, clear all of the steps on all of the
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# tracks.
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@self.on_hold(self.start_stop)
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def start_stop_hold(key):
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if self.track_selector_active:
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self.clear_tracks()
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# Attach hold function that lights the tempo down/up keys when the
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# tempo selector key is held.
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@self.on_hold(self.tempo_selector)
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def tempo_selector_hold(key):
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self.tempo_select_active = True
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self.tempo_down.set_led(*TEMPO_DOWN_COLOUR)
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self.tempo_up.set_led(*TEMPO_UP_COLOUR)
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# Attach release function that furns off the tempo down/up LEDs.
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@self.on_release(self.tempo_selector)
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def tempo_selector_release(key):
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self.tempo_select_active = False
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self.tempo_down.led_off()
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self.tempo_up.led_off()
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def update(self):
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# Update the superclass (Keybow2040).
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super(Sequencer, self).update()
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if self.running:
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# Keep track of current time.
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current_time = time.monotonic()
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# If a step has elapsed...
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if current_time - self.last_step_time > self.step_time:
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for track in self.tracks:
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if track.active:
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# Turn last step off.
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last_step = track.steps[self.last_step_num]
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last_step.playing = False
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last_step.update()
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last_note = last_step.note
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# If last step is active, send MIDI note off message.
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if last_step.active:
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self.midi_channels[track.channel].send(NoteOff(last_note, 0))
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# Turn this step on.
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this_step = track.steps[self.this_step_num]
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this_step.playing = True
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this_step.update()
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this_note = this_step.note
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this_vel = this_step.velocity
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# If this step is active, send MIDI note on message.
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if this_step.active:
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self.midi_channels[track.channel].send(NoteOn(this_note, this_vel))
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# This step is now the last step!
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last_step = this_step
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self.last_step_num = self.this_step_num
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self.this_step_num += 1
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# If we get to the end of the sequence, go back to the start.
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if self.this_step_num == self.num_steps:
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self.this_step_num = 0
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# Keep track of last step time.
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self.last_step_time = current_time
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# Update the tracks.
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for track in self.tracks:
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track.update()
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# Update the step_time, in case the BPM has been changed.
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self.step_time = 60.0 / self.bpm / (self.num_steps / 2)
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def clear_tracks(self):
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# Clears the steps on all tracks.
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for track in self.tracks:
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track.clear_steps()
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class Track:
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"""
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Represents a track on the sequencer.
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:param sequencer: the parent sequencer instance
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:param index: the index of the track, integer
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:param channel: the MIDI channel, integer
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:param rgb: the RGB colour of the track, tuple of R, G, B, 0-255.
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"""
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def __init__(self, sequencer, index, channel, rgb):
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self.index = index
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self.rgb = rgb
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self.channel = channel
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self.steps = []
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self.sequencer = sequencer
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# For each key in the track, create a Step instance and add to
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# self.steps.
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for i in range(len(TRACK_KEYS)):
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index = i
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key = sequencer.keys[TRACK_KEYS[i]]
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step = Step(index, key, self)
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self.steps.append(step)
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# Default to having the track active.
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self.active = True
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self.focussed = False
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def set_on(self):
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# Toggle the track on.
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self.active = True
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def set_off(self):
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# Toggle the track off.
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self.active = False
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def update(self):
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# Make the current track focussed and update its steps.
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if sequencer.current_track == self.index:
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self.focussed = True
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self.update_steps()
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else:
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self.focussed = False
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def update_steps(self):
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# Update a tracks steps.
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for step in self.steps:
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step.update()
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def clear_steps(self):
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# Clear a track's steps by setting them all to inactive.
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for step in self.steps:
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step.active = False
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class Step:
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"""
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Represents a step on a track.
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:param index: the index of the step, integer
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:param key: the key attached to this step, integer
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:param track: the track this step belongs to, Track instance.
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"""
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def __init__(self, index, key, track):
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self.index = index
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self.key = key
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self.track = track
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self.active = False
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self.playing = False
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self.velocity = 127
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self.note = 60
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self.rgb = self.track.rgb
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self.sequencer = self.track.sequencer
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def toggle(self):
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# Toggle the step between active and inactive.
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self.active = not self.active
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def state(self):
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# Returns the state of the track (active/inactve).
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return self.active
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def set_led(self, r, g, b, brightness):
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# Set the step's LED. Has an additional brightness parameter from 0.0
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# (off) to 1.0 (full brightness for the colour).
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r, g, b = [int(c * brightness) for c in (r, g, b)]
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self.key.set_led(r, g, b)
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def update(self):
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# Update the step. Pretty much just handles the LEDs.
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r, g, b = self.rgb
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# If this step's track is focussed...
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if self.track.focussed:
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# Only update the LEDs when the sequencer is running.
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if self.sequencer.running:
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# Make an active step that is currently being played full
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# brightness.
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if self.playing and self.active:
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self.set_led(r, g, b, PLAY_BRIGHTNESS)
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# Make an inactive step that is "playing" (the current step)
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# the dimmest brightness, but bright enough to indicate the
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# step the sequencer is on.
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if self.playing and not self.active:
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self.set_led(r, g, b, STEP_BRIGHTNESS)
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# Make an active step that is not playing a low-medium
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# brightness to indicate that it is toggled active.
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if not self.playing and self.active:
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self.set_led(r, g, b, ACTIVE_BRIGHTNESS)
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# Turn not playing, not active steps off.
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if not self.playing and not self.active:
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self.set_led(0, 0, 0, 0)
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# If the sequencer is not running, still show the active steps.
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elif not self.sequencer.running:
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if self.active:
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self.set_led(r, g, b, 0.3)
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else:
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self.set_led(0, 0, 0, 0)
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# Set up Keybow
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i2c = board.I2C()
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# Instatiate the sequencer.
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sequencer = Sequencer(i2c)
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while True:
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# Always remember to call sequencer.update() on every iteration of the main
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# loop, otherwise NOTHING WILL WORK!
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sequencer.update() |