example_05_filters.py

# SPDX-FileCopyrightText: 2023 John Park and @todbot / Tod Kurt
#
# SPDX-License-Identifier: MIT

import time
import board
import digitalio
import audiomixer
import synthio

# for PWM audio with an RC filter
# import audiopwmio
# audio = audiopwmio.PWMAudioOut(board.GP10)

# for I2S audio with external I2S DAC board
import audiobusio

# I2S on Audio BFF or Amp BFF on QT Py:
# audio = audiobusio.I2SOut(bit_clock=board.A3, word_select=board.A2, data=board.A1)

# I2S audio on PropMaker Feather RP2040
power = digitalio.DigitalInOut(board.EXTERNAL_POWER)
power.switch_to_output(value=True)
audio = audiobusio.I2SOut(board.I2S_BIT_CLOCK, board.I2S_WORD_SELECT, board.I2S_DATA)

mixer = audiomixer.Mixer(channel_count=1, sample_rate=22050, buffer_size=2048)

amp_env_slow = synthio.Envelope(
                                attack_time=0.2,
                                sustain_level=1.0,
                                release_time=0.8
)

synth = synthio.Synthesizer(channel_count=1, sample_rate=22050, envelope=amp_env_slow)

# set up filters
frequency = 2000
resonance = 1.5
lpf = synth.low_pass_filter(frequency, resonance)
hpf = synth.high_pass_filter(frequency, resonance)
bpf = synth.band_pass_filter(frequency, resonance)

note1 = synthio.Note(frequency=330, filter=None)

audio.play(mixer)
mixer.voice[0].play(synth)
mixer.voice[0].level = 0.2

while True:
    # no filter
    note1.filter = None
    synth.press(note1)
    time.sleep(1.25)
    synth.release(note1)
    time.sleep(1.25)

    # lpf
    note1.filter = lpf
    synth.press(note1)
    time.sleep(1.25)
    synth.release(note1)
    time.sleep(1.25)

    # hpf
    note1.filter = hpf
    synth.press(note1)
    time.sleep(1.25)
    synth.release(note1)
    time.sleep(1.25)

    # bpf
    note1.filter = bpf
    synth.press(note1)
    time.sleep(1.25)
    synth.release(note1)
    time.sleep(1.25)