apps/codecs/libgme/gb_apu.h

   1 // Nintendo Game Boy sound hardware emulator with save state support
   2
   3 // Gb_Snd_Emu 0.1.4
   4 #ifndef GB_APU_H
   5 #define GB_APU_H
   6
   7 #include "gb_oscs.h"
   8
   9 // Clock rate sound hardware runs at
  10 enum { clock_rate = 4194304 * GB_APU_OVERCLOCK };
  11
  12 // Registers are at io_addr to io_addr+io_size-1
  13 enum { io_addr = 0xFF10 };
  14 enum { io_size = 0x30 };
  15 enum { regs_size = io_size + 0x10 };
  16
  17 enum gb_mode_t {
  18         mode_dmg,   // Game Boy monochrome
  19         mode_cgb,   // Game Boy Color
  20         mode_agb    // Game Boy Advance
  21 };
  22
  23 // 0: Square 1, 1: Square 2, 2: Wave, 3: Noise
  24 enum { osc_count = 4 }; // 0 <= chan < osc_count
  25
  26 struct Gb_Apu {
  27         struct Gb_Osc*     oscs [osc_count];
  28         blip_time_t last_time;          // time sound emulator has been run to
  29         blip_time_t frame_period;       // clocks between each frame sequencer step
  30         double      volume_;
  31         bool        reduce_clicks_;
  32
  33         struct Gb_Square square1;
  34         struct Gb_Square square2;
  35         struct Gb_Wave   wave;
  36         struct Gb_Noise  noise;
  37         blip_time_t     frame_time;     // time of next frame sequencer action
  38         int             frame_phase;    // phase of next frame sequencer step
  39
  40         uint8_t  regs [regs_size];// last values written to registers
  41
  42         // large objects after everything else
  43         struct Blip_Synth synth;
  44 };
  45
  46 // Basics
  47
  48 // Initializes apu
  49 void Apu_init( struct Gb_Apu* this );
  50
  51 // Emulates to time t, then writes data to addr
  52 void Apu_write_register( struct Gb_Apu* this, blip_time_t t, int addr, int data ) ICODE_ATTR;
  53
  54 // Emulates to time t, then subtracts t from the current time.
  55 // OK if previous write call had time slightly after t.
  56 void Apu_end_frame( struct Gb_Apu* this,blip_time_t t ) ICODE_ATTR;
  57
  58 // More features
  59
  60 // Emulates to time t, then reads from addr
  61 int Apu_read_register( struct Gb_Apu* this, blip_time_t t, int addr ) ICODE_ATTR;
  62
  63 // Resets hardware to state after power, BEFORE boot ROM runs. Mode selects
  64 // sound hardware. If agb_wave is true, enables AGB's extra wave features.
  65 void Apu_reset( struct Gb_Apu* this, enum gb_mode_t mode, bool agb_wave );
  66
  67 // Same as set_output(), but for a particular channel
  68 void Apu_set_output( struct Gb_Apu* this, int chan, struct Blip_Buffer* center,
  69                 struct Blip_Buffer* left, struct Blip_Buffer* right );
  70
  71 // Sets overall volume, where 1.0 is normal
  72 void Apu_volume( struct Gb_Apu* this, double v );
  73
  74 // If true, reduces clicking by disabling DAC biasing. Note that this reduces
  75 // emulation accuracy, since the clicks are authentic.
  76 void Apu_reduce_clicks( struct Gb_Apu* this, bool reduce );
  77
  78 // Sets frame sequencer rate, where 1.0 is normal. Meant for adjusting the
  79 // tempo in a music player.
  80 void Apu_set_tempo( struct Gb_Apu* this, int t );
  81
  82
  83 void write_osc( struct Gb_Apu* this, int reg, int old_data, int data ) ICODE_ATTR;
  84
  85 #endif