phase accumulation oscillator experiment in circuitpython

phase_accum_oscillator.py

# phase accumulation oscillator experiment
# 13 Nov 2023 - @todbot
# basically just copying
#   https://github.com/wntrblm/Sol/blob/master/firmware/winterbloom_sol/lfo.py
#

import time
import math
from supervisor import ticks_ms

class LFO:
    def __init__(self, frequency):
        self.frequency = frequency
        self._phase = 0
        self._last_millis = ticks_ms()

    def _phase_accumulate(self):
        now = ticks_ms()
        time_delta = now - self._last_millis
        self._last_millis = now
        phase_accum = (time_delta/1000) * self.frequency
        self._phase = (self._phase + phase_accum) % 1.0

    @property
    def value(self):
        """Output the LFO value, defaults to sine wave"""
        self._phase_accumulate()
        return math.sin(math.pi * 2 * self._phase)

class TriangleLFO(LFO):
    @property
    def value(self):
        self._phase_accumulate()
        return (abs(self._phase - 0.5) * 4.0) - 1.0

class SampleLFO(LFO):
    def __init__(self, frequency, sample):
        super().__init__(frequency)
        self._sample = sample

    @property
    def value(self):
        self._phase_accumulate()
        i = int(self._phase * len(self._sample))
        return self._sample[i]

sample_length = 16
cos_wave = [
    math.cos(math.pi * 2 * i / sample_length)
    for i in range(sample_length)
]
my_sample = cos_wave

o1 = LFO(frequency=0.6)
o2 = TriangleLFO(frequency=0.1)
o3 = SampleLFO(frequency=0.6, sample=my_sample)

while True:
    print("%+.2f %+.2f %+.2f" % (o1.value, o2.value, o3.value) )
    time.sleep(0.05)

output looks like: