tone-generator/tone.hpp

#pragma once

#include <inttypes.h>
#include "util.hpp"

struct Tone {

	enum Type {
		tt_sine     = 0,
		tt_saw      = 1,
		tt_square   = 2,
		tt_triangle = 3,
	};

	uint32_t phase;
	uint16_t frequency;
	uint8_t amplitude;
	Type mode;

	inline static int8_t sin_lookup[256];

	static void init();

	inline bool active() const AW_IN {
		return amplitude > 0;
	}

	inline void update(uint32_t t) AW_IN {
		phase += t * frequency;
	}

	inline int get() const AW_IN {
		int v;
		switch(mode) {
		case tt_sine:
			v = sin_lookup[(phase >> 12) & 255];
			break;
		case tt_saw:
			v = (int8_t)((phase >> 12) & 255);
			break;
		case tt_square:
			v = phase & 0x80000 ? -127 : 127;
			break;
		case tt_triangle:
			v = (phase >> 11) & 0x1ff;
			v = (v > 0xff ? 1 : -1) * (int8_t)phase;
			break;
		}
		return v * amplitude;
	}
};