synth.h

#ifndef SYNTHH
#define SYNTHH

#include <stdint.h>

#define F_SAMPLE (48ul*1000) /* 48kHz sample rate */

/* convert floating-point number in [-1, 1] to integer in [min, max] */
#define LVL(x, min, max) ((x) >= 1.0 ? (max) : (x) <= -1.0 ? (min) : (x) * (max))
#define LVLU32(x) (LVL(x, 0, UINT32_MAX))
#define LVLS32(x) (LVL(x, INT32_MIN, INT32_MAX))

// #define ENVELOPE_STEP(delta_lvl, delta_time) {LVLS32(delta_lvl) / (delta_time), (delta_time)}

#define FIXED_POINT 8
// TODO: Might want to assert f < +/-2^23
/* Float to Fixed Point */
#define F2FP(f) (int32_t)(f * (1<<FIXED_POINT))

#define SYNTH_WAVEGEN_COUNT 32
#define WAVEGEN_ENVELOPE_LENGTH 8

enum {
    WAVEGEN_SHAPE_SAWTOOTH = 0,
    WAVEGEN_SHAPE_SQUARE = 1,
    WAVEGEN_SHAPE_SINE = 2,
    WAVEGEN_SHAPE_PIANO = 3,
    WAVEGEN_SHAPE_FLUTE = 4,
    WAVEGEN_SHAPE_GUITAR = 5,
    NUM_WAVEGEN_SHAPES
};

enum {
    WAVEGEN_CMD_REWIND_ENVELOPE = 1<<0,
    WAVEGEN_CMD_ENABLE = 1<<1,
};

enum {
    LOOPER_CMD_CLEAR = 1<<0,
    LOOPER_CMD_REWIND = 1<<1,
};

typedef volatile struct PACKED {
    int16_t rate; /* change per milliseconds */
    uint8_t duration; /* milliseconds */
} EnvelopeStep;

typedef volatile struct PACKED {
    uint32_t freq /* FIXED POINT */;
    uint32_t velocity /* FIXED POINT */;
    EnvelopeStep envelope[WAVEGEN_ENVELOPE_LENGTH];
    uint8_t shape;
    uint8_t cmds;
} Wavegen;

// ! Not used
// typedef volatile struct PACKED {
//     uint32_t delay;
//     uint32_t feedback;
// } Echo;

typedef volatile struct PACKED {
    int32_t balance; /* Interpreted as in range [-1, 1] */
} Pan;

typedef volatile struct PACKED {
    uint32_t tau[6];
    uint32_t gain[7] /* FIXED_POINT */;
} Reverb;

typedef volatile struct PACKED {
    Wavegen wavegens[SYNTH_WAVEGEN_COUNT];
    uint32_t master_volume;
    Reverb reverb;
    Pan pan;
} Synth;

void wavegen_set_vol_envelope(Wavegen *self, const EnvelopeStep *steps);
void wavegen_clearcmds(Wavegen *self);
void synth_clearcmds(Synth *self);

#endif