Matt Spencer
496b6bdc71
Key components: - no_std core so it can be used bare metal on embedded systems - default implementation for RPi 2350, with midi input and I2s output using PIO - Visualiser for the web to play with on a dev system
63 lines
1.7 KiB
Rust
63 lines
1.7 KiB
Rust
//! Voltage-controlled oscillator (VCO).
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//!
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//! Waveforms: Sine, Saw, Square, Triangle, Pulse (variable width).
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//! Uses phase accumulation; bandlimited variants (BLEP/BLAMP) to follow.
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use crate::{AudioProcessor, CVProcessor, config::SampleRate};
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#[derive(Clone, Copy, Debug, PartialEq)]
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pub enum Waveform {
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Sine,
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Saw,
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Square,
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Triangle,
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Pulse(f32), // pulse width 0.0–1.0
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}
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pub struct Vco {
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pub waveform: Waveform,
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pub freq_hz: f32,
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phase: f32,
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sample_rate: SampleRate,
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}
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impl Vco {
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pub fn new(sample_rate: SampleRate, freq_hz: f32, waveform: Waveform) -> Self {
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Self { waveform, freq_hz, phase: 0.0, sample_rate }
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}
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#[inline]
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fn next_sample(&mut self) -> f32 {
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let p = self.phase;
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let sample = match self.waveform {
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Waveform::Sine => libm::sinf(p * core::f32::consts::TAU),
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Waveform::Saw => 2.0 * p - 1.0,
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Waveform::Square => if p < 0.5 { 1.0 } else { -1.0 },
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Waveform::Triangle => 4.0 * (p - libm::floorf(p + 0.5)).abs() - 1.0,
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Waveform::Pulse(w) => if p < w { 1.0 } else { -1.0 },
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};
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let next = p + self.freq_hz * self.sample_rate.period();
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self.phase = next - libm::floorf(next);
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sample
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}
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}
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impl<const B: usize> AudioProcessor<B> for Vco {
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fn process(&mut self, out: &mut [f32; B]) {
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for s in out.iter_mut() {
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*s = self.next_sample();
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}
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}
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fn reset(&mut self) {
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self.phase = 0.0;
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}
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}
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impl<const B: usize> CVProcessor<B> for Vco {
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/// CV is 1 V/oct: 0 V = 440 Hz, +1 V = 880 Hz, −1 V = 220 Hz.
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fn set_cv(&mut self, cv: f32) {
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self.freq_hz = 440.0 * libm::powf(2.0, cv);
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}
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}
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