machine_gameboyadvance.go

// +build gameboyadvance

package machine

import (
	"image/color"
	"runtime/volatile"
	"unsafe"
)

var (
	// IO maps the I/O Peripherals.
	IO = (*IORegs)(unsafe.Pointer(uintptr(0x04000000)))
)

// IOMap is the memory mapping of the IO Registers.
//
// Full IO Map:
//   https://www.akkit.org/info/gbatek.htm#gbaiomap
type IORegs struct {
	LCD    LCDRegs
	Sound  SoundRegs
	_      [0x100 - 0x0B0]byte // DMA
	Timer  [4]Timer            // Timers
	_      [0x10]byte          // Unused
	_      [0x130 - 0x120]byte // Serial 1
	Keypad Keypad
	_      [0x200 - 0x134]byte // Serial 2
	Int    InterruptRegs
}

type LCDRegs struct {
	DISPCNT  volatile.Register16 // R/W - LCD Control
	_        volatile.Register16 // R/W - Undocumented - Green Swap
	DISPSTAT volatile.Register16 // R/W - General LCD Status (STAT,LYC)
	VCOUNT   volatile.Register16 // R   - Vertical Counter (LY)
	BG0CNT   volatile.Register16 // R/W - BG0 Control
	BG1CNT   volatile.Register16 // R/W - BG1 Control
	BG2CNT   volatile.Register16 // R/W - BG2 Control
	BG3CNT   volatile.Register16 // R/W - BG3 Control
	BG0HOFS  volatile.Register16 // W   - BG0 X-Offset
	BG0VOFS  volatile.Register16 // W   - BG0 Y-Offset
	BG1HOFS  volatile.Register16 // W   - BG1 X-Offset
	BG1VOFS  volatile.Register16 // W   - BG1 Y-Offset
	BG2HOFS  volatile.Register16 // W   - BG2 X-Offset
	BG2VOFS  volatile.Register16 // W   - BG2 Y-Offset
	BG3HOFS  volatile.Register16 // W   - BG3 X-Offset
	BG3VOFS  volatile.Register16 // W   - BG3 Y-Offset
	BG2PA    volatile.Register16 // W   - BG2 Rotation/Scaling Parameter A (dx)
	BG2PB    volatile.Register16 // W   - BG2 Rotation/Scaling Parameter B (dmx)
	BG2PC    volatile.Register16 // W   - BG2 Rotation/Scaling Parameter C (dy)
	BG2PD    volatile.Register16 // W   - BG2 Rotation/Scaling Parameter D (dmy)
	BG2X     volatile.Register32 // W   - BG2 Reference Point X-Coordinate
	BG2Y     volatile.Register32 // W   - BG2 Reference Point Y-Coordinate
	BG3PA    volatile.Register16 // W   - BG3 Rotation/Scaling Parameter A (dx)
	BG3PB    volatile.Register16 // W   - BG3 Rotation/Scaling Parameter B (dmx)
	BG3PC    volatile.Register16 // W   - BG3 Rotation/Scaling Parameter C (dy)
	BG3PD    volatile.Register16 // W   - BG3 Rotation/Scaling Parameter D (dmy)
	BG3X     volatile.Register32 // W   - BG3 Reference Point X-Coordinate
	BG3Y     volatile.Register32 // W   - BG3 Reference Point Y-Coordinate
	WIN0H    volatile.Register16 // W   - Window 0 Horizontal Dimensions
	WIN1H    volatile.Register16 // W   - Window 1 Horizontal Dimensions
	WIN0V    volatile.Register16 // W   - Window 0 Vertical Dimensions
	WIN1V    volatile.Register16 // W   - Window 1 Vertical Dimensions
	WININ    volatile.Register16 // R/W - Inside of Window 0 and 1
	WINOUT   volatile.Register16 // R/W - Inside of OBJ Window & Outside of Windows
	MOSAIC   volatile.Register16 // W   - Mosaic Size
	_        volatile.Register16 // -   - Not used
	BLDCNT   volatile.Register16 // R/W - Color Special Effects Selection
	BLDALPHA volatile.Register16 // W   - Alpha Blending Coefficients
	BLDY     volatile.Register16 // W   - Brightness (Fade-In/Out) Coefficient
	_        volatile.Register32 // -   - Not used
	_        volatile.Register32 // -   - Not used
}

// DISPCNT Register Constants
const (
	DISPCNT_MODE1 = 1
	DISPCNT_MODE2 = 2
	DISPCNT_MODE3 = 3
	DISPCNT_MODE4 = 4
	DISPCNT_MODE5 = 5

	DISPCNT_FRAME_SELECT         = 1 << 4
	DISPCNT_HBLANK_INTERVAL_FREE = 1 << 5
	DISPCNT_OBJ_VRAM_MAP_1D      = 1 << 6
	DISPCNT_FORCED_BLANK         = 1 << 7
	DISPCNT_DISPLAY_BG0          = 1 << 8
	DISPCNT_DISPLAY_BG1          = 1 << 9
	DISPCNT_DISPLAY_BG2          = 1 << 10
	DISPCNT_DISPLAY_BG3          = 1 << 11
	DISPCNT_DISPLAY_OBJ          = 1 << 12

	DISPCNT_MODE_MASK = 0x7
	DISPCNT_BG_MASK   = 0xf << 8
)

// DISPSTAT Register Constants
const (
	DISPSTAT_VBLANK       = 1 << iota // V-Blank flag   (Read only) (1=VBlank) (set in line 160..226; not 227)
	DISPSTAT_HBLANK                   // H-Blank flag   (Read only) (1=HBlank) (toggled in all lines, 0..227)
	DISPSTAT_VCOUNTER                 // V-Counter flag (Read only) (1=Match)  (set in selected line)
	DISPSTAT_VBLANK_IRQ               // V-Blank IRQ Enable         (1=Enable)
	DISPSTAT_HBLANK_IRQ               // H-Blank IRQ Enable         (1=Enable)
	DISPSTAT_VCOUNTER_IRQ             // V-Counter IRQ Enable       (1=Enable)
)

type SoundRegs struct {
	SOUND1CNT_L volatile.Register16    // R/W - Channel 1 Sweep register       (NR10)
	SOUND1CNT_H volatile.Register16    // R/W - Channel 1 Duty/Length/Envelope (NR11, NR12)
	SOUND1CNT_X volatile.Register16    // R/W - Channel 1 Frequency/Control    (NR13, NR14)
	_           volatile.Register16    // -   - Not used
	SOUND2CNT_L volatile.Register16    // R/W - Channel 2 Duty/Length/Envelope (NR21, NR22)
	_           volatile.Register16    // -   - Not used
	SOUND2CNT_H volatile.Register16    // R/W - Channel 2 Frequency/Control    (NR23, NR24)
	_           volatile.Register16    // -   - Not used
	SOUND3CNT_L volatile.Register16    // R/W - Channel 3 Stop/Wave RAM select (NR30)
	SOUND3CNT_H volatile.Register16    // R/W - Channel 3 Length/Volume        (NR31, NR32)
	SOUND3CNT_X volatile.Register16    // R/W - Channel 3 Frequency/Control    (NR33, NR34)
	_           volatile.Register16    // -   - Not used
	SOUND4CNT_L volatile.Register16    // R/W - Channel 4 Length/Envelope      (NR41, NR42)
	_           volatile.Register16    // -   - Not used
	SOUND4CNT_H volatile.Register16    // R/W - Channel 4 Frequency/Control    (NR43, NR44)
	_           volatile.Register16    // -   - Not used
	SOUNDCNT_L  volatile.Register16    // R/W - Control Stereo/Volume/Enable   (NR50, NR51)
	SOUNDCNT_H  volatile.Register16    // R/W - Control Mixing/DMA Control
	SOUNDCNT_X  volatile.Register16    // R/W - Control Sound on/off           (NR52)
	_           volatile.Register16    // -   - Not used
	SOUNDBIAS   volatile.Register16    // BIAS- Sound PWM Control
	_           [3]volatile.Register16 // -   - Not used
	WAVE_RAM    [2][8]byte             // R/W - Channel 3 Wave Pattern RAM (2 banks!!)
	FIFO_A      volatile.Register32    // W   - Channel A FIFO, Data 0-3
	FIFO_B      volatile.Register32    // W   - Channel B FIFO, Data 0-3
	_           [4]volatile.Register16 // Not used
}

type InterruptRegs struct {
	Request volatile.Register16 // R/W - Interrupt Request
	Ack     volatile.Register16 // R/W - Interrupt Active (R) / Acknowledge (W)
	_       volatile.Register32 // -   - Not used
	Enable  volatile.Register16 // R/W - Interrupt Master Enable
}

type PinMode uint8

// Set has not been implemented.
func (p Pin) Set(value bool) {
	// do nothing
}

var (
	DisplayMode3 = Mode3DisplayBuffer{(*[160][240]volatile.Register16)(unsafe.Pointer(uintptr(0x06000000)))}
	Display      = DisplayMode3 // default to the Mode3 display buffer.
)

type Mode3DisplayBuffer struct {
	port *[160][240]volatile.Register16
}

func (d Mode3DisplayBuffer) Configure() {
	// Use video mode 3 (in BG2, a 16bpp bitmap in VRAM) and
	// Enable BG2 (BG0 = 1, BG1 = 2, BG2 = 4, ...)
	IO.LCD.DISPCNT.Set(DISPCNT_MODE3 | DISPCNT_DISPLAY_BG2)
}

func (d Mode3DisplayBuffer) Size() (x, y int16) {
	return 240, 160
}

func (d Mode3DisplayBuffer) SetPixel(x, y int16, c color.RGBA) {
	d.port[y][x].Set(uint16(c.R)&0x1f | uint16(c.G)&0x1f<<5 | uint16(c.B)&0x1f<<10)
}

func (d Mode3DisplayBuffer) Display() error {
	// disable forced blank so we can see screen
	IO.LCD.DISPCNT.ClearBits(DISPCNT_FORCED_BLANK)

	return nil
}

type Keypad struct {
	Status  volatile.Register16 // R   - Key Status
	Control volatile.Register16 // R/W - Key Interrupt Control
}

// A Key represents one of the possible keys.
type Key uint16

// Keypad constants
const (
	KEY_A Key = 1 << iota
	KEY_B
	KEY_SELECT
	KEY_START
	KEY_RIGHT
	KEY_LEFT
	KEY_UP
	KEY_DOWN
	KEY_RB
	KEY_LB

	// KEY_ANY has the bits for every key set.
	KEY_ANY Key = 0x3FF

	KEY_IRQ_ENABLE = 1 << 14
	KEY_IRQ_ALL    = 1 << 15
)

func (k *Keypad) WakeOn(keys ...Key) {
	var mask uint16
	for _, k := range keys {
		mask |= uint16(k)
	}
	k.Control.ClearBits(uint16(KEY_ANY))
	k.Control.SetBits(mask)
}

type Timer struct {
	Counter volatile.Register16 // R/W - Counter (R) / Reload (W)
	Control volatile.Register16 // R/W - Flags (see TIMER_*)
}

// Timer constants
const (
	TIMER_PRESCALE_1      = 0
	TIMER_PRESCALE_64     = 1
	TIMER_PRESCALE_256    = 2
	TIMER_PRESCALE_1024   = 3
	TIMER_COUNT_OVERFLOWS = 1 << 2
	TIMER_IRQ_ENABLE      = 1 << 6
	TIMER_START           = 1 << 7
)

func (t *Timer) Start() {
	t.Control.SetBits(TIMER_START)
}

func (t *Timer) Stop() {
	t.Control.ClearBits(TIMER_START)
}