Trinkey MIDI Theremin with Pitch! (will also work on any other CircuitPython devices with `touchio`)

trinkey_theremin_pitch_code.py

# trinkey_theremin_pitch_code.py -- Trinkey MIDI Theremin! with pitch control!
# 2021 @todbot
# left antenna: pitch (by multiple MIDI notes, put your synth in legato mode)
# right antenna: filter cutoff
# video demo in comment below
#
import time
import board
import neopixel
import touchio
import usb_midi
import adafruit_midi
from adafruit_midi.note_on          import NoteOn
from adafruit_midi.control_change   import ControlChange

midi = adafruit_midi.MIDI(midi_out=usb_midi.ports[1], out_channel=0)
leds = neopixel.NeoPixel(board.NEOPIXEL, 4, brightness=0.2, auto_write=True)

# announce we're alive and wait for things to stabilize
# before creating touch pins so their raw_value baseline are okay
leds.fill(0xff00ff)
time.sleep(1.0)
leds.fill(0)

touch1_pin = touchio.TouchIn(board.TOUCH1)
touch2_pin = touchio.TouchIn(board.TOUCH2)

# a litlte helper class for noise filtering
class RunningAverage:
    def __init__(self,count):
        self.count = count
        self.i = 0
        self.buf = [0] * self.count
    def add_value(self,val):
        self.buf[self.i] = val
        self.i = (self.i + 1) % self.count
    def average(self):
        return sum(self.buf)/self.count

base1 = int(touch1_pin.raw_value * 1.02)
base2 = int(touch2_pin.raw_value * 1.02)

avg1 = RunningAverage(8)
avg2 = RunningAverage(8)

note_on = False

note_base = 48  # C3 in MIDI land
note = note_base
velocity = 64  # half 

while True:
    avg1.add_value( touch1_pin.raw_value )
    avg2.add_value( touch2_pin.raw_value )

    r = 0
    g = min(max(avg1.average()-base1, 0),255)
    b = min(max(avg2.average()-base2, 0),255)
    
    leds.fill( (r,g,b) )

    if g > 10:   # hand present
        note_new = note_base + int(g/4)
        if note_new != note:
            print(time.monotonic(),"******* ON! ",note_new,note)
            midi.send(NoteOn(note_new, velocity)) # turn on new note
            midi.send(NoteOn(note,0)) # 0=off  # turn off old note
            note = note_new  # save new note

    else: # no hand, turn off note
        midi.send(NoteOn(note,0)) # 0=off
    
    if b > 10:  # hand present
        midi.send(ControlChange( 74, 16+int(b/2.5)))  # 74 = filter cutoff

    time.sleep(0.001)

Video demo of above code:

trinkey_midi_theramin.mp4

yes "theramin" is spelled wrong :)