WIP

cartridge.go

@@ -1,301 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"encoding/binary"
-	"io"
-	"log"
-	"os"
-)
-
-// See https://gbdev.io/pandocs/The_Cartridge_Header.html#0104-0133--nintendo-logo
-var expectedLogo = [48]byte{
-	0xCE, 0xED, 0x66, 0x66, 0xCC, 0x0D, 0x00, 0x0B,
-	0x03, 0x73, 0x00, 0x83, 0x00, 0x0C, 0x00, 0x0D,
-	0x00, 0x08, 0x11, 0x1F, 0x88, 0x89, 0x00, 0x0E,
-	0xDC, 0xCC, 0x6E, 0xE6, 0xDD, 0xDD, 0xD9, 0x99,
-	0xBB, 0xBB, 0x67, 0x63, 0x6E, 0x0E, 0xEC, 0xCC,
-	0xDD, 0xDC, 0x99, 0x9F, 0xBB, 0xB9, 0x33, 0x3E,
-}
-
-// Cartridge types
-// See https://gbdev.io/pandocs/The_Cartridge_Header.html#0147--cartridge-type
-var cartridgeTypes = map[byte]string{
-	0x00: "ROM ONLY",
-	0x01: "MBC1",
-	0x02: "MBC1+RAM",
-	0x03: "MBC1+RAM+BATTERY",
-	0x05: "MBC2",
-	0x06: "MBC2+BATTERY",
-	0x08: "ROM+RAM 9",
-	0x09: "ROM+RAM+BATTERY 9",
-	0x0B: "MMM01",
-	0x0C: "MMM01+RAM",
-	0x0D: "MMM01+RAM+BATTERY",
-	0x0F: "MBC3+TIMER+BATTERY",
-	0x10: "MBC3+TIMER+RAM+BATTERY 10",
-	0x11: "MBC3",
-	0x12: "MBC3+RAM 10",
-	0x13: "MBC3+RAM+BATTERY 10",
-	0x19: "MBC5",
-	0x1A: "MBC5+RAM",
-	0x1B: "MBC5+RAM+BATTERY",
-	0x1C: "MBC5+RUMBLE",
-	0x1D: "MBC5+RUMBLE+RAM",
-	0x1E: "MBC5+RUMBLE+RAM+BATTERY",
-	0x20: "MBC6",
-	0x22: "MBC7+SENSOR+RUMBLE+RAM+BATTERY",
-	0xFC: "POCKET CAMERA",
-	0xFD: "BANDAI TAMA5",
-	0xFE: "HuC3",
-	0xFF: "HuC1+RAM+BATTERY",
-}
-
-// RAM sizes
-// https://gbdev.io/pandocs/The_Cartridge_Header.html#0149--ram-size
-var ramSizes = map[byte]string{
-	0x00: "0 - No RAM",
-	0x01: "UNUSED VALUE",
-	0x02: "8 KiB - 1 bank",
-	0x03: "32 KiB - 4 banks of 8 KiB each",
-	0x04: "128 KiB 16 banks of 8 KiB each",
-	0x05: "64 KiB  8 banks of 8 KiB each",
-}
-
-// Old licensees
-// https://gbdev.io/pandocs/The_Cartridge_Header.html#014b--old-licensee-code
-var oldLicensees = map[byte]string{
-	0x00: "None",
-	0x01: "Nintendo",
-	0x08: "Capcom",
-	0x09: "HOT-B",
-	0x0A: "Jaleco",
-	0x0B: "Coconuts Japan",
-	0x0C: "Elite Systems",
-	0x13: "EA (Electronic Arts)",
-	0x18: "Hudson Soft",
-	0x19: "ITC Entertainment",
-	0x1A: "Yanoman",
-	0x1D: "Japan Clary",
-	0x1F: "Virgin Games Ltd.3",
-	0x24: "PCM Complete",
-	0x25: "San-X",
-	0x28: "Kemco",
-	0x29: "SETA Corporation",
-	0x30: "Infogrames5",
-	0x31: "Nintendo",
-	0x32: "Bandai",
-	0x33: "Indicates that the New licensee code should be used instead.",
-	0x34: "Konami",
-	0x35: "HectorSoft",
-	0x38: "Capcom",
-	0x39: "Banpresto",
-	0x3C: "Entertainment Interactive (stub)",
-	0x3E: "Gremlin",
-	0x41: "Ubi Soft1",
-	0x42: "Atlus",
-	0x44: "Malibu Interactive",
-	0x46: "Angel",
-	0x47: "Spectrum HoloByte",
-	0x49: "Irem",
-	0x4A: "Virgin Games Ltd.3",
-	0x4D: "Malibu Interactive",
-	0x4F: "U.S. Gold",
-	0x50: "Absolute",
-	0x51: "Acclaim Entertainment",
-	0x52: "Activision",
-	0x53: "Sammy USA Corporation",
-	0x54: "GameTek",
-	0x55: "Park Place13",
-	0x56: "LJN",
-	0x57: "Matchbox",
-	0x59: "Milton Bradley Company",
-	0x5A: "Mindscape",
-	0x5B: "Romstar",
-	0x5C: "Naxat Soft14",
-	0x5D: "Tradewest",
-	0x60: "Titus Interactive",
-	0x61: "Virgin Games Ltd.3",
-	0x67: "Ocean Software",
-	0x69: "EA (Electronic Arts)",
-	0x6E: "Elite Systems",
-	0x6F: "Electro Brain",
-	0x70: "Infogrames5",
-	0x71: "Interplay Entertainment",
-	0x72: "Broderbund",
-	0x73: "Sculptured Software6",
-	0x75: "The Sales Curve Limited7",
-	0x78: "THQ",
-	0x79: "Accolade15",
-	0x7A: "Triffix Entertainment",
-	0x7C: "MicroProse",
-	0x7F: "Kemco",
-	0x80: "Misawa Entertainment",
-	0x83: "LOZC G.",
-	0x86: "Tokuma Shoten",
-	0x8B: "Bullet-Proof Software2",
-	0x8C: "Vic Tokai Corp.16",
-	0x8E: "Ape Inc.17",
-	0x8F: "I'Max18",
-	0x91: "Chunsoft Co.8",
-	0x92: "Video System",
-	0x93: "Tsubaraya Productions",
-	0x95: "Varie",
-	0x96: "Yonezawa19/S'Pal",
-	0x97: "Kemco",
-	0x99: "Arc",
-	0x9A: "Nihon Bussan",
-	0x9B: "Tecmo",
-	0x9C: "Imagineer",
-	0x9D: "Banpresto",
-	0x9F: "Nova",
-	0xA1: "Hori Electric",
-	0xA2: "Bandai",
-	0xA4: "Konami",
-	0xA6: "Kawada",
-	0xA7: "Takara",
-	0xA9: "Technos Japan",
-	0xAA: "Broderbund",
-	0xAC: "Toei Animation",
-	0xAD: "Toho",
-	0xAF: "Namco",
-	0xB0: "Acclaim Entertainment",
-	0xB1: "ASCII Corporation or Nexsoft",
-	0xB2: "Bandai",
-	0xB4: "Square Enix",
-	0xB6: "HAL Laboratory",
-	0xB7: "SNK",
-	0xB9: "Pony Canyon",
-	0xBA: "Culture Brain",
-	0xBB: "Sunsoft",
-	0xBD: "Sony Imagesoft",
-	0xBF: "Sammy Corporation",
-	0xC0: "Taito",
-	0xC2: "Kemco",
-	0xC3: "Square",
-	0xC4: "Tokuma Shoten",
-	0xC5: "Data East",
-	0xC6: "Tonkin House",
-	0xC8: "Koei",
-	0xC9: "UFL",
-	0xCA: "Ultra Games",
-	0xCB: "VAP, Inc.",
-	0xCC: "Use Corporation",
-	0xCD: "Meldac",
-	0xCE: "Pony Canyon",
-	0xCF: "Angel",
-	0xD0: "Taito",
-	0xD1: "SOFEL (Software Engineering Lab)",
-	0xD2: "Quest",
-	0xD3: "Sigma Enterprises",
-	0xD4: "ASK Kodansha Co.",
-	0xD6: "Naxat Soft14",
-	0xD7: "Copya System",
-	0xD9: "Banpresto",
-	0xDA: "Tomy",
-	0xDB: "LJN",
-	0xDD: "Nippon Computer Systems",
-	0xDE: "Human Ent.",
-	0xDF: "Altron",
-	0xE0: "Jaleco",
-	0xE1: "Towa Chiki",
-	0xE2: "Yutaka # Needs more info",
-	0xE3: "Varie",
-	0xE5: "Epoch",
-	0xE7: "Athena",
-	0xE8: "Asmik Ace Entertainment",
-	0xE9: "Natsume",
-	0xEA: "King Records",
-	0xEB: "Atlus",
-	0xEC: "Epic/Sony Records",
-	0xEE: "IGS",
-	0xF0: "A Wave",
-	0xF3: "Extreme Entertainment",
-	0xFF: "LJN",
-}
-
-type ROMHeader struct {
-	EntryPoint [4]byte
-	Logo       [48]byte
-	// NOTE(m): Assuming "old" cartridges here. This may cause problems with newer cartridges.
-	// See https://gbdev.io/pandocs/The_Cartridge_Header.html#0134-0143--title
-	Title                [16]byte
-	NewLicenseeCode      [2]byte
-	SGBFlag              byte
-	CartridgeType        byte
-	ROMSize              byte
-	RAMSize              byte
-	DestinationCode      byte
-	OldLicenseeCode      byte
-	MaskROMVersionNumber byte
-	HeaderChecksum       byte
-	GlobalChecksum       [2]byte
-}
-
-type Cartridge struct {
-	Filename    string
-	Mapper      string
-	Title       string
-	Licensee    string
-	SGBSupport  bool
-	ROMSize     int
-	RAMSize     string
-	Destination string
-	Version     int
-}
-
-func Insert(filename string) Cartridge {
-	file, err := os.Open(filename)
-	if err != nil {
-		log.Fatal(err)
-	}
-	defer file.Close()
-	cartridge := Cartridge{Filename: file.Name()}
-
-	// Jump to start of header
-	_, err = file.Seek(0x0100, io.SeekStart)
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	// Read header
-	var header ROMHeader
-	err = binary.Read(file, binary.LittleEndian, &header)
-	if err != nil {
-		log.Fatal(err)
-	}
-
-	// Validate the ROM by checking presence of the Nintendo logo
-	if header.Logo != expectedLogo {
-		log.Fatal("Invalid ROM file: No valid logo found!")
-	}
-
-	// Convert some header values
-	cartridge.Title = string(bytes.Trim(header.Title[:], "\x00"))
-	cartridge.Mapper = cartridgeTypes[header.CartridgeType]
-	if header.OldLicenseeCode == 0x33 {
-		// FIXME(m): Support new licensee codes
-		cartridge.Licensee = "Indicates that the New licensee code should be used instead."
-	} else {
-		cartridge.Licensee = oldLicensees[header.OldLicenseeCode]
-	}
-	cartridge.SGBSupport = (header.SGBFlag == 0x03)
-	cartridge.ROMSize = 32 * (1 << header.ROMSize)
-	cartridge.RAMSize = ramSizes[header.RAMSize]
-	switch header.DestinationCode {
-	case 0x00:
-		cartridge.Destination = "Japan (and possibly overseas)"
-	case 0x01:
-		cartridge.Destination = "Overseas only"
-	default:
-		cartridge.Destination = "UNKNOWN"
-	}
-	cartridge.Version = int(header.MaskROMVersionNumber)
-
-	// TODO(m): Verify header checksum
-
-	// NOTE(m): Ignoring global checksum which is not used, except by one emulator.
-	// See https://gbdev.io/pandocs/The_Cartridge_Header.html#014e-014f--global-checksum
-
-	return cartridge
-}

gb/bus.go

@@ -0,0 +1,35 @@
+package gb
+
+// import (
+// 	"fmt"
+// )
+
+// type Bus struct {
+// 	Cart *Cartridge
+// }
+
+// func NewBus(cart *Cartridge) *Bus {
+// 	bus := Bus{Cart: cart}
+
+// 	return &bus
+// }
+
+// func (bus *Bus) Read(address uint16) (byte, error) {
+// 	if address < 0x8000 {
+// 		// ROM data
+// 		return bus.Cart.Read(address), nil
+// 	} else {
+// 		return 0, fmt.Errorf("Reading from address %X not implemented!", address)
+// 	}
+// }
+
+// func (bus *Bus) Write(address uint16, value byte) error {
+// 	if address < 0x8000 {
+// 		// ROM data
+// 		bus.Cart.Write(address, value)
+
+// 		return nil
+// 	} else {
+// 		return fmt.Errorf("Writing to address %X not implemented!", address)
+// 	}
+// }

gb/cartridge.go

@@ -3,8 +3,7 @@ package gb
 import (
 	"bytes"
 	"encoding/binary"
-	"io"
-	"log"
+	"fmt"
 	"os"
 )
 
@@ -215,6 +214,7 @@ var oldLicensees = map[byte]string{
 }
 
 type ROMHeader struct {
+	_          [256]byte
 	EntryPoint [4]byte
 	Logo       [48]byte
 	// NOTE(m): Assuming "old" cartridges here. This may cause problems with newer cartridges.
@@ -228,7 +228,7 @@ type ROMHeader struct {
 	DestinationCode      byte
 	OldLicenseeCode      byte
 	MaskROMVersionNumber byte
-	HeaderChecksum       byte
+	Checksum             byte
 	GlobalChecksum       [2]byte
 }
 
@@ -242,32 +242,23 @@ type Cartridge struct {
 	RAMSize     string
 	Destination string
 	Version     int
+	Checksum    byte
 }
 
-func InsertCartridge(path string) *Cartridge {
-	file, err := os.Open(path)
-	if err != nil {
-		log.Fatal(err)
-	}
-	defer file.Close()
-	cartridge := Cartridge{Filename: file.Name()}
+func InsertCartridge(filename string) (*Cartridge, error) {
+	cartridge := Cartridge{Filename: filename}
 
-	// Jump to start of header
-	_, err = file.Seek(0x0100, io.SeekStart)
+	rom, err := os.ReadFile(filename)
 	if err != nil {
-		log.Fatal(err)
+		return &cartridge, err
 	}
 
 	// Read header
 	var header ROMHeader
-	err = binary.Read(file, binary.LittleEndian, &header)
+	buffer := bytes.NewReader(rom)
+	err = binary.Read(buffer, binary.LittleEndian, &header)
 	if err != nil {
-		log.Fatal(err)
-	}
-
-	// Validate the ROM by checking presence of the Nintendo logo
-	if header.Logo != expectedLogo {
-		log.Fatal("Invalid ROM file: No valid logo found!")
+		return &cartridge, nil
 	}
 
 	// Convert some header values
@@ -292,10 +283,16 @@ func InsertCartridge(path string) *Cartridge {
 	}
 	cartridge.Version = int(header.MaskROMVersionNumber)
 
-	// TODO(m): Verify header checksum
+	// Calculate and verify checksum
+	for address := uint16(0x0134); address <= uint16(0x014C); address++ {
+		cartridge.Checksum = cartridge.Checksum - rom[address] - 1
+	}
+	if cartridge.Checksum != header.Checksum {
+		return &cartridge, fmt.Errorf("ROM checksum failed: %X does not equal %X", cartridge.Checksum, header.Checksum)
+	}
 
 	// NOTE(m): Ignoring global checksum which is not used, except by one emulator.
 	// See https://gbdev.io/pandocs/The_Cartridge_Header.html#014e-014f--global-checksum
 
-	return &cartridge
+	return &cartridge, nil
 }

gb/cartridge_test.go

@@ -1,4 +1,4 @@
-package main
+package gb
 
 import (
 	"testing"
@@ -6,10 +6,13 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestInsertCartridge(t *testing.T) {
-	cartridge := Insert("./roms/dmg-acid2.gb")
+func TestInsert(t *testing.T) {
+	cartridge, err := InsertCartridge("../roms/dmg-acid2.gb")
+
 	assert := assert.New(t)
 
+	assert.Nil(err)
+	assert.Equal(cartridge.Filename, "../roms/dmg-acid2.gb")
 	assert.Equal(cartridge.Title, "DMG-ACID2")
 	assert.Equal(cartridge.Mapper, "ROM ONLY")
 	assert.Equal(cartridge.Licensee, "None")
@@ -18,4 +21,11 @@ func TestInsertCartridge(t *testing.T) {
 	assert.Equal(cartridge.RAMSize, "0 - No RAM")
 	assert.Equal(cartridge.Destination, "Japan (and possibly overseas)")
 	assert.Equal(cartridge.Version, 0)
+	assert.Equal(cartridge.Checksum, byte(0x9F))
+}
+
+func TestFailedChecksum(t *testing.T) {
+	_, err := InsertCartridge("../roms/failed-checksum.gb")
+
+	assert.EqualError(t, err, "ROM checksum failed: 9F does not equal 41")
 }

gb/console.go

@@ -11,15 +11,19 @@ const (
 )
 
 type Console struct {
+	CPU       *CPU
 	Cartridge *Cartridge
 	front     *image.RGBA
 }
 
 func NewConsole(path string) (*Console, error) {
-	cartridge := InsertCartridge(path)
+	cartridge, err := InsertCartridge(path)
+	if err != nil {
+		return &Console{}, err
+	}
 	buffer := image.NewRGBA(image.Rect(0, 0, ConsoleWidth, ConsoleHeight))
 
-	console := Console{Cartridge: cartridge, front: buffer}
+	console := Console{Cartridge: cartridge, CPU: NewCPU(), front: buffer}
 
 	return &console, nil
 }

gb/cpu.go

@@ -0,0 +1,45 @@
+package gb
+
+const CPUFrequency = 4194304
+
+type Registers struct {
+	A  byte
+	F  byte
+	B  byte
+	C  byte
+	D  byte
+	E  byte
+	H  byte
+	L  byte
+	PC uint16
+	SP uint16
+}
+
+type CPU struct {
+	Regs                Registers
+	FetchedData         uint16
+	MemoryDestination   uint16
+	DestinationIsMemory bool
+	CurrentOPcode       byte
+	// CurrentInstruction     *Instruction
+	Halted                 bool
+	Stepping               bool
+	InterruptMasterEnabled bool
+}
+
+func NewCPU() *CPU {
+	cpu := CPU{}
+	cpu.Regs = Registers{}
+	cpu.Stepping = true
+
+	return &cpu
+}
+
+func (cpu *CPU) Step() bool {
+	if cpu.Stepping {
+		cpu.Stepping = false
+		return true
+	}
+
+	return false
+}

main.go

@@ -1,9 +1,15 @@
 package main
 
 import (
-	"gb-player/ui"
+	"fmt"
+	"log"
+
+	// "gb-player/ui"
+	"gb-player/gb"
 )
 
+var running = true
+
 func main() {
 	// FIXME(m): Allow specifying rom file on command line
 	// if len(os.Args) != 2 {
@@ -12,5 +18,20 @@ func main() {
 	// romPath := os.Args[1]
 	romPath := "./roms/dmg-acid2.gb"
 
-	ui.Run(romPath)
+	// ui.Run(romPath)
+
+	console, err := gb.NewConsole(romPath)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	running := true
+	for running {
+		if !console.CPU.Step() {
+			fmt.Println("CPU stopped")
+			running = false
+		} else {
+			fmt.Println("CPU step")
+		}
+	}
 }

ui/controller.go

@@ -51,10 +51,15 @@ func (c *Controller) Run() {
 	running := true
 	for running {
 		for event := sdl.PollEvent(); event != nil; event = sdl.PollEvent() {
-			switch event.(type) {
+			switch e := event.(type) {
 			case *sdl.QuitEvent:
-				println("Quit")
 				running = false
+			case *sdl.KeyboardEvent:
+				if e.Type == sdl.KEYDOWN {
+					if e.Keysym.Sym == sdl.K_ESCAPE {
+						running = false
+					}
+				}
 			}
 		}
 

ui/view.go

@@ -22,8 +22,7 @@ func (view *View) Update(dt uint64) {
 	console := view.console
 	renderer := view.controller.renderer
 
-	// console.StepMilliSeconds(dt)
-	console.StepMilliSeconds(sdl.GetTicks64())
+	console.StepMilliSeconds(dt)
 
 	buffer := console.Buffer()