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Adding code for MIDI to CV guide
Adding code for the MIDI to CV learn guide. Takes in MIDI messages over USB and outputs gate and 1V/oct. volts.py is a helper file for comparing MIDI note numbers and 1V/oct values
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‎MIDI_to_CV_Skull/code.py‎

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# SPDX-FileCopyrightText: 2022 Liz Clark for Adafruit Industries
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# SPDX-License-Identifier: MIT
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import board
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import simpleio
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import adafruit_mcp4725
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import usb_midi
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import adafruit_midi
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from digitalio import DigitalInOut, Direction
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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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from volts import volts
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# midi channel setup
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midi_in_channel = 1
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midi_out_channel = 1
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# USB midi setup
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midi = adafruit_midi.MIDI(
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midi_in=usb_midi.ports[0], in_channel=0, midi_out=usb_midi.ports[1], out_channel=0
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)
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# gate output pin
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gate = DigitalInOut(board.A1)
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gate.direction = Direction.OUTPUT
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# i2c setup
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i2c = board.I2C()
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# dac setup over i2c
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dac = adafruit_mcp4725.MCP4725(i2c)
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# dac raw value (12 bit)
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dac.raw_value = 4095
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# array for midi note numbers
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midi_notes = []
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# array for 12 bit 1v/oct values
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pitches = []
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# function to map 1v/oct voltages to 12 bit values
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# these values are added to the pitches[] array
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def map_volts(n, volt, vref, bits):
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n = simpleio.map_range(volt, 0, vref, 0, bits)
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pitches.append(n)
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# brings values from volts.py into individual arrays
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for v in volts:
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# map_volts function to map 1v/oct values to 12 bit
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# and append to pitches[]
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map_volts(v['label'], v['1vOct'], 5, 4095)
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# append midi note numbers to midi_notes[] array
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midi_notes.append(v['midi'])
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while True:
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# read incoming midi messages
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msg = midi.receive()
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# if a midi msg comes in...
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if msg is not None:
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# if it's noteoff...
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if isinstance(msg, NoteOff):
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# send 0 volts on dac
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dac.raw_value = 0
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# turn off gate pin
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gate.value = False
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# if it's noteon...
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if isinstance(msg, NoteOn):
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# compare incoming note number to midi_notes[]
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z = midi_notes.index(msg.note)
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# limit note range to defined notes in volts.py
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if msg.note < 36:
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msg.note = 36
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if msg.note > 96:
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msg.note = 96
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# send corresponding 1v/oct value
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dac.raw_value = int(pitches[z])
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# turn on gate pin
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gate.value = True

‎MIDI_to_CV_Skull/volts.py‎

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# SPDX-FileCopyrightText: 2022 Liz Clark for Adafruit Industries
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# SPDX-License-Identifier: MIT
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# Helper file for MIDI note number to 1V/oct voltage
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volts = [
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{'label':"C-2",'midi':36,'1vOct':0.000},
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{'label':"C♯2",'midi':37,'1vOct':0.083},
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{'label':"D-2",'midi':38,'1vOct':0.167},
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{'label':"D♯2",'midi':39,'1vOct':0.250},
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{'label':"E-2",'midi':40,'1vOct':0.333},
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{'label':"F-2",'midi':41,'1vOct':0.417},
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{'label':"F♯2",'midi':42,'1vOct':0.500},
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{'label':"G-2",'midi':43,'1vOct':0.583},
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{'label':"G♯2",'midi':44,'1vOct':0.667},
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{'label':"A-2",'midi':45,'1vOct':0.750},
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{'label':"A♯2",'midi':46,'1vOct':0.833},
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{'label':"B-2",'midi':47,'1vOct':0.917},
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{'label':"C-3",'midi':48,'1vOct':1.000},
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{'label':"C♯3",'midi':49,'1vOct':1.083},
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{'label':"D-3",'midi':50,'1vOct':1.167},
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{'label':"D♯3",'midi':51,'1vOct':1.250},
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{'label':"E-3",'midi':52,'1vOct':1.333},
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{'label':"F-3",'midi':53,'1vOct':1.417},
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{'label':"F♯3",'midi':54,'1vOct':1.500},
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{'label':"G-3",'midi':55,'1vOct':1.583},
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{'label':"G♯3",'midi':56,'1vOct':1.667},
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{'label':"A-3",'midi':57,'1vOct':1.750},
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{'label':"A♯3",'midi':58,'1vOct':1.833},
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{'label':"B-3",'midi':59,'1vOct':1.917},
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{'label':"C-4",'midi':60,'1vOct':2.000},
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{'label':"C♯4",'midi':61,'1vOct':2.083},
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{'label':"D-4",'midi':62,'1vOct':2.167},
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{'label':"D♯4",'midi':63,'1vOct':2.250},
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{'label':"E-4",'midi':64,'1vOct':2.333},
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{'label':"F-4",'midi':65,'1vOct':2.417},
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{'label':"F♯4",'midi':66,'1vOct':2.500},
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{'label':"G-4",'midi':67,'1vOct':2.583},
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{'label':"G♯4",'midi':68,'1vOct':2.667},
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{'label':"A-4",'midi':69,'1vOct':2.750},
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{'label':"A♯4",'midi':70,'1vOct':2.833},
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{'label':"B-4",'midi':71,'1vOct':2.917},
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{'label':"C-5",'midi':72,'1vOct':3.000},
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{'label':"C♯5",'midi':73,'1vOct':3.083},
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{'label':"D-5",'midi':74,'1vOct':3.167},
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{'label':"D♯5",'midi':75,'1vOct':3.250},
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{'label':"E-5",'midi':76,'1vOct':3.333},
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{'label':"F-5",'midi':77,'1vOct':3.417},
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{'label':"F♯5",'midi':78,'1vOct':3.500},
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{'label':"G-5",'midi':79,'1vOct':3.583},
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{'label':"G♯5",'midi':80,'1vOct':3.667},
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{'label':"A-5",'midi':81,'1vOct':3.750},
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{'label':"A♯5",'midi':82,'1vOct':3.833},
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{'label':"B-5",'midi':83,'1vOct':3.917},
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{'label':"C-6",'midi':84,'1vOct':4.000},
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{'label':"C♯6",'midi':85,'1vOct':4.083},
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{'label':"D-6",'midi':86,'1vOct':4.167},
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{'label':"D♯6",'midi':87,'1vOct':4.250},
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{'label':"E-6",'midi':88,'1vOct':4.333},
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{'label':"F-6",'midi':89,'1vOct':4.417},
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{'label':"F♯6",'midi':90,'1vOct':4.500},
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{'label':"G-6",'midi':91,'1vOct':4.583},
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{'label':"G♯6",'midi':92,'1vOct':4.667},
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{'label':"A-6",'midi':93,'1vOct':4.750},
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{'label':"A♯6",'midi':94,'1vOct':4.833},
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{'label':"B-6",'midi':95,'1vOct':4.917},
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{'label':"C-7",'midi':96,'1vOct':5.000},
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]

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