nese/src/ppu.h

#ifndef NES_PPU_H_
#define NES_PPU_H_

#include <stdint.h>


struct nes_mapper_t;
struct nes_cart_t;


#define DBG_LOG(...) printf(__VA_ARGS__)

#ifdef DEBUG_OAM
#define OAM_LOG DBG_LOG
#else
#define OAM_LOG(...)
#endif
#ifdef DEBUG_VRAM
#define VRAM_LOG DBG_LOG
#else
#define VRAM_LOG(...)
#endif
#ifdef DEBUG_PPU
#define PPU_LOG DBG_LOG
#else
#define PPU_LOG(...)
#endif
#ifdef DEBUG_RENDER
#define REND_LOG DBG_LOG
#else
#define REND_LOG(...)
#endif


#define nes_ppu_dots        (341U)
#define nes_ppu_prerender   (1U)
#define nes_ppu_height      (240U)
#define nes_ppu_postrender  (1U)
#define nes_ppu_vblank      (20U)

#define nes_ppu_active  (nes_ppu_prerender + \
                         nes_ppu_height +    \
                         nes_ppu_postrender)

#define nes_ppu_frame   (nes_ppu_active + nes_ppu_vblank)

#define nes_ppu_active_cycles   (nes_ppu_dots * nes_ppu_active)
#define nes_ppu_vblank_cycles   (nes_ppu_dots * nes_ppu_vblank)

#define nes_ppu_frame_cycles    (nes_ppu_dots * nes_ppu_frame)

#define nes_ppu_scan_w  (320U) // Effective NTSC horizontal rez
#define nes_ppu_scan_h  nes_ppu_height

#define nes_ppu_blocks_w    (32U)
#define nes_ppu_blocks_h    (30U)

#define nes_ppu_render_w    (nes_ppu_blocks_w * 8U)
#define nes_ppu_render_h    (nes_ppu_blocks_h * 8U)

#define nes_ppu_mem_size        (0x4000U)
#define nes_ppu_mem_chr_start   (0x0000U)
#define nes_ppu_mem_chr_size    (0x2000U)
#define nes_ppu_mem_vram_start  (0x2000U)
#define nes_ppu_mem_vram_size   (0x1000U)
#define nes_ppu_mem_pal_start   (0x3F00U)
#define nes_ppu_mem_pal_size    (0x0020U)


#define nes_ppu_oam_size    (256U)

#define nes_ppu_oam_sprite_size     (4U)
#define nes_ppu_oam_sprite_count    (nes_ppu_oam_size / \
                                     nes_ppu_oam_sprite_size)

typedef enum {
    ppu_Control_Nametable_Mask  = 0b00000011,
    ppu_Control_Scroll_Page_X   = 0b00000001,
    ppu_Control_Scroll_Page_Y   = 0b00000010,
    ppu_Control_VRAM_Inc        = 0b00000100,
    ppu_Control_Sprite_Bank     = 0b00001000,
    ppu_Control_Back_Bank       = 0b00010000,
    ppu_Control_Sprite_Size     = 0b00100000,
    ppu_Control_Master          = 0b01000000,
    ppu_Control_VBlank          = 0b10000000,
} nes_ppu_Control;

typedef enum {
    ppu_Status_Open_Bus_Mask    = 0b00011111,
    ppu_Status_Overflow         = 0b00100000,
    ppu_Status_Hit              = 0b01000000,
    ppu_Status_VBlank           = 0b10000000,
} nes_ppu_Status;

typedef enum {
    ppu_Mask_Greyscale      = 0b00000001,
    ppu_Mask_Left_Back      = 0b00000010,
    ppu_Mask_Left_Sprite    = 0b00000100,
    ppu_Mask_Back           = 0b00001000,
    ppu_Mask_Sprite         = 0b00010000,
    ppu_Mask_More_Red       = 0b00100000,
    ppu_Mask_More_Green     = 0b01000000,
    ppu_Mask_More_Blue      = 0b10000000,
} nes_ppu_Mask;

typedef struct {
    // Memory
    struct nes_mapper_t* mapper;
    uint8_t oam[nes_ppu_oam_size];
    uint8_t palette[nes_ppu_mem_pal_size];

    // Timing
    int frame;
    int scanline;
    int cycle;

    int hit_line;
    int hit_dot;

    // External registers
    uint8_t control;
    uint8_t mask;
    uint8_t status;
    uint8_t scroll_x;
    uint8_t scroll_y;
    uint16_t addr;
    uint8_t data;
    uint8_t oam_addr;

    // Internal Registers
    uint8_t latch;

} nes_ppu;

uint8_t nes_ppu_read(nes_ppu* ppu, uint16_t addr);
void nes_ppu_write(nes_ppu* ppu, uint16_t addr, uint8_t val);
void nes_ppu_reset(nes_ppu* ppu);
int nes_ppu_init(nes_ppu* ppu, const struct nes_cart_t*);

typedef enum {
    ppu_Result_Halt     = -1,
    ppu_Result_Running  = 0U,
    ppu_Result_VBlank_On,
    ppu_Result_VBlank_Off,
    ppu_Result_Ready,
} nes_ppu_Result;

nes_ppu_Result nes_ppu_run(nes_ppu* ppu, int cycles);


#endif // NES_PPU_H_