circuitpython-playground-lightsynth.py

# CircuitPlaygroundExpress Light Synth
#
# reads a potentiometer from A7, changes NeoPixels
# and audio tone
#
# slide switch turns off sound, button a changes sample

from analogio import AnalogIn
import board
import neopixel
import time

analogin = AnalogIn(board.A7)

def interp(val, fromMin, fromMax, toMin, toMax):
    return ((val - fromMin) / (fromMax-fromMin)) * (toMax - toMin) + toMin

def getVoltage(pin):  # helper
    return (pin.value * 3.3) / 65536

def wheel(pos):
    # Input a value 0 to 255 to get a color value.
    # The colours are a transition r - g - b - back to r.
    if pos < 85:
        return (int(pos*3), int(255 - (pos*3)), 0)
    elif pos < 170:
        pos -= 85
        return (int(255 - (pos*3)), 0, int(pos*3))
    else:
        pos -= 170
        return (0, int(pos*3), int(255 - pos*3))

# https://stackoverflow.com/questions/12332392/triangle-wave-shaped-array-in-python
def triangle(length, amplitude):
     section = length // 4
     for direction in (1, -1):
         for i in range(section):
             yield i * (amplitude / section) * direction
         for i in range(section):
             yield (amplitude - (i * (amplitude / section))) * direction

pixels = neopixel.NeoPixel(board.NEOPIXEL, 10, brightness=.2)
pixels.fill((0,0,0))
pixels.show()


from digitalio import DigitalInOut, Direction, Pull
import audioio
import math
import array


FREQUENCY = 440    # 440 Hz middle 'A'
SAMPLERATE = 8000  # 8000 samples/second, recommended!

# Generate one period of sine wav.
length = SAMPLERATE // FREQUENCY
print("generate wave with length %i" % (length))

sine_wave = array.array("H", [0] * length)
square_wave = array.array("H", [0] * length)
triangle_wave = array.array("H", [ int(n) for n in triangle(length, FREQUENCY) ])

for i in range(length):
    sine_wave[i] = int(math.sin(math.pi * 2 * i / 18) * (2 ** 15) + 2 ** 15)
    square_wave[i] = 0 if i < 6 == 0 else FREQUENCY

print(sine_wave)
print(square_wave)
print(triangle_wave)

waves = [ sine_wave, square_wave, triangle_wave ]

# enable the speaker
spkrenable = DigitalInOut(board.SPEAKER_ENABLE)
spkrenable.direction = Direction.OUTPUT
spkrenable.value = True

def get_sample(i):
    return audioio.AudioOut(board.SPEAKER, waves[i])

sample = get_sample(0)

switch = DigitalInOut(board.SLIDE_SWITCH)
switch.direction = Direction.INPUT
switch.pull = Pull.UP

button = DigitalInOut(board.BUTTON_A)
button.direction = Direction.INPUT
button.pull = Pull.DOWN

def tone(volt, samp):
    samp.frequency = int(interp(volt, 0, 3.3, 6000, 8000))
    samp.play(loop=True)  # keep playing the sample over and over

def stop(samp):
    samp.stop()

last_volt = 0
wave_idx = 0

# this is the bit that repeats
while True:
    volt = getVoltage(analogin)
    pixels.fill(wheel(interp(volt, 0, 3.3, 0, 255)))
    pixels.show()
    if abs(volt - last_volt) > 0.2:
        #print(volt)
        if switch.value == True:  # switch is pushed
            sample.frequency = int(interp(volt, 0, 3.3, 6000, 8000))
            sample.play(loop=True)  # keep playing the sample over and over

        last_volt = volt

    if button.value == True:
        wave_idx = (wave_idx + 1) % len(waves)
        stop(sample)
        sample = get_sample(wave_idx)
        sample.frequency = int(interp(volt, 0, 3.3, 6000, 8000))
        sample.play(loop=True)  # keep playing the sample over and over

    if switch.value == False:  # switch is pushed
        stop(sample)