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// Private oscillators used by Gb_Apu
// Gb_Snd_Emu 0.1.4
#ifndef GB_OSCS_H
#define GB_OSCS_H
#include "blargg_common.h"
#include "blip_buffer.h"
#ifndef GB_APU_OVERCLOCK
#define GB_APU_OVERCLOCK 1
#endif
#if GB_APU_OVERCLOCK & (GB_APU_OVERCLOCK - 1)
#error "GB_APU_OVERCLOCK must be a power of 2"
#endif
enum { clk_mul = GB_APU_OVERCLOCK };
enum { dac_bias = 7 };
struct Gb_Osc {
struct Blip_Buffer* outputs [4];// NULL, right, left, center
struct Blip_Buffer* output; // where to output sound
uint8_t* regs; // osc's 5 registers
int mode; // mode_dmg, mode_cgb, mode_agb
int dac_off_amp;// amplitude when DAC is off
int last_amp; // current amplitude in Blip_Buffer
struct Blip_Synth* synth;
int delay; // clocks until frequency timer expires
int length_ctr; // length counter
unsigned phase; // waveform phase (or equivalent)
bool enabled; // internal enabled flag
};
// 11-bit frequency in NRx3 and NRx4
static inline int Osc_frequency( struct Gb_Osc* this ) { return (this->regs [4] & 7) * 0x100 + this->regs [3]; }
void Osc_clock_length( struct Gb_Osc* this );
void Osc_reset( struct Gb_Osc* this );
// Square
enum { period_mask = 0x70 };
enum { shift_mask = 0x07 };
struct Gb_Square {
struct Gb_Osc osc;
int env_delay;
int volume;
bool env_enabled;
// Sweep square
int sweep_freq;
int sweep_delay;
bool sweep_enabled;
bool sweep_neg;
};
void Square_run( struct Gb_Square* this, blip_time_t, blip_time_t );
void Square_clock_envelope( struct Gb_Square* this );
static inline void Square_reset( struct Gb_Square* this )
{
this->env_delay = 0;
this->volume = 0;
Osc_reset( &this->osc );
this->osc.delay = 0x40000000; // TODO: something less hacky (never clocked until first trigger)
}
// Frequency timer period
static inline int Square_period( struct Gb_Square* this ) { return (2048 - Osc_frequency( &this->osc )) * (4 * clk_mul); }
static inline int Square_dac_enabled( struct Gb_Square* this) { return this->osc.regs [2] & 0xF8; }
static inline int Square_reload_env_timer( struct Gb_Square* this )
{
int raw = this->osc.regs [2] & 7;
this->env_delay = (raw ? raw : 8);
return raw;
}
// Sweep square
void clock_sweep( struct Gb_Square* this );
static inline void Sweep_reset( struct Gb_Square* this )
{
this->sweep_freq = 0;
this->sweep_delay = 0;
this->sweep_enabled = false;
this->sweep_neg = false;
this->env_delay = 0;
this->volume = 0;
Osc_reset( &this->osc );
this->osc.delay = 0x40000000; // TODO: something less hacky (never clocked until first trigger)
}
// Noise
#define period2_mask (0x1FFFF)
struct Gb_Noise {
struct Gb_Osc osc;
int env_delay;
int volume;
bool env_enabled;
int divider; // noise has more complex frequency divider setup
};
void Noise_run( struct Gb_Noise* this, blip_time_t, blip_time_t );
static inline void Noise_reset( struct Gb_Noise* this )
{
this->divider = 0;
this->env_delay = 0;
this->volume = 0;
Osc_reset( &this->osc );
this->osc.delay = 4 * clk_mul; // TODO: remove?
}
void Noise_clock_envelope( struct Gb_Noise* this );
// Non-zero if DAC is enabled
static inline int Noise_dac_enabled( struct Gb_Noise* this) { return this->osc.regs [2] & 0xF8; }
static inline int Noise_reload_env_timer( struct Gb_Noise* this )
{
int raw = this->osc.regs [2] & 7;
this->env_delay = (raw ? raw : 8);
return raw;
}
static inline int period2_index( struct Gb_Noise* this ) { return this->osc.regs [3] >> 4; }
static inline int period2( struct Gb_Noise* this, int base ) { return base << period2_index( this ); }
static inline unsigned lfsr_mask( struct Gb_Noise* this ) { return (this->osc.regs [3] & 0x08) ? ~0x4040 : ~0x4000; }
// Wave
enum { bank40_mask = 0x40 };
enum { wave_bank_size = 32 };
struct Gb_Wave {
struct Gb_Osc osc;
int sample_buf; // last wave RAM byte read (hardware has this as well)
int agb_mask; // 0xFF if AGB features enabled, 0 otherwise
uint8_t* wave_ram; // 32 bytes (64 nybbles), stored in APU
};
void Wave_run( struct Gb_Wave* this, blip_time_t, blip_time_t );
static inline void Wave_reset( struct Gb_Wave* this )
{
this->sample_buf = 0;
Osc_reset( &this->osc );
}
// Frequency timer period
static inline int Wave_period( struct Gb_Wave* this ) { return (2048 - Osc_frequency( &this->osc )) * (2 * clk_mul); }
// Non-zero if DAC is enabled
static inline int Wave_dac_enabled( struct Gb_Wave* this ) { return this->osc.regs [0] & 0x80; }
static inline uint8_t* wave_bank( struct Gb_Wave* this ) { return &this->wave_ram [(~this->osc.regs [0] & bank40_mask) >> 2 & this->agb_mask]; }
// Wave index that would be accessed, or -1 if no access would occur
int wave_access( struct Gb_Wave* this, int addr );
// Reads/writes wave RAM
static inline int Wave_read( struct Gb_Wave* this, int addr )
{
int index = wave_access( this, addr );
return (index < 0 ? 0xFF : wave_bank( this ) [index]);
}
static inline void Wave_write( struct Gb_Wave* this, int addr, int data )
{
int index = wave_access( this, addr );
if ( index >= 0 )
wave_bank( this ) [index] = data;;
}
#endif
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