rough start to flash

src/crab/bus.cr

@@ -8,8 +8,6 @@ class Bus
   end
 
   def [](index : Int) : Byte
-    return 0x62_u8 if index == 0x0E000000
-    return 0x13_u8 if index == 0x0E000001
     log "read #{hex_str index.to_u32}"
     case bits(index, 24..27)
     when 0x0 then @bios[index & 0x3FFF]
@@ -25,7 +23,7 @@ class Bus
     when 0x8, 0x9,
          0xA, 0xB,
          0xC, 0xD then @gba.cartridge[index & 0x01FFFFFF]
-    when 0xE then @gba.cartridge.sram[index & 0xFFFF]
+    when 0xE then @gba.flash[index & 0xFFFF]
     else          abort "Unmapped read: #{hex_str index.to_u32}"
     end
   end
@@ -80,7 +78,7 @@ class Bus
       @gba.ppu.vram[address] = value
     when 0x7      then @gba.ppu.oam[index & 0x3FF] = value
     when 0x8, 0x9 then log "Writing to cart - #{hex_str index.to_u32}: #{hex_str value}"
-    when 0xE      then @gba.cartridge.sram[index & 0xFFFF] = value
+    when 0xE      then @gba.flash[index & 0xFFFF] = value
     else               abort "Unmapped write: #{hex_str index.to_u32}"
     end
   end

src/crab/cartridge.cr

@@ -1,6 +1,5 @@
 class Cartridge
   getter rom : Bytes
-  getter sram = Bytes.new 0x10000
 
   getter title : String {
     io = IO::Memory.new

src/crab/flash.cr

@@ -0,0 +1,89 @@
+class Flash
+  enum Type
+    EEPROM
+    SRAM
+    FLASH
+    FLASH512
+    FLASH1M
+
+    def regex : Regex
+      /#{self}_V\d{3}/
+    end
+  end
+
+  enum State
+    READY
+    CMD_1
+    CMD_2
+  end
+
+  enum Command : Byte
+    ENTER_IDENT   = 0x90
+    EXIT_IDENT    = 0xF0
+    PREPARE_ERASE = 0x80
+    ERASE_ALL     = 0x10
+    ERASE_CHUNK   = 0x30
+    PREPARE_WRITE = 0xA0
+    SET_BANK      = 0xB0
+  end
+
+  SANYO = 0x1362_u16
+
+  getter! type : Type
+  @save_path : String
+  @sram = Bytes.new 0x10000, 0xFF
+  @state = State::READY
+  @identification_mode = false
+
+  def initialize(rom_path : String)
+    File.open(rom_path, "rb") do |file|
+      str = file.gets_to_end
+      Type.each do |type|
+        if type.regex.matches?(str)
+          @type = type
+          break
+        end
+      end
+    end
+    unless @type
+      puts "Falling back to SRAM since backup type could not be identified.".colorize.fore(:red)
+      @type = Type::SRAM
+    end
+    puts "Backup type: #{@type}"
+    @save_path = rom_path.gsub(/\.gba$/, ".sav")
+    @save_path += ".sav" unless @save_path.ends_with?(".sav")
+    puts "Save path: #{@save_path}"
+  end
+
+  def [](index : Int) : Byte
+    puts "#{hex_str index.to_u16}"
+    if @identification_mode && 0 <= index <= 1
+      (SANYO >> (8 * index) & 0xFF).to_u8!
+    else
+      @sram[index]
+    end
+  end
+
+  def []=(index : Int, value : Byte) : Nil
+    puts "#{hex_str index.to_u16} -> #{hex_str value}        #{@state}"
+    case @state
+    in State::READY
+      @state = State::CMD_1 if value == 0xAA
+    in State::CMD_1
+      @state = State::CMD_2 if value == 0x55
+    in State::CMD_2
+      case value
+      when Command::ENTER_IDENT.value then @identification_mode = true
+      when Command::EXIT_IDENT.value  then @identification_mode = false
+      when Command::PREPARE_ERASE.value
+      when Command::ERASE_ALL.value
+      when Command::ERASE_CHUNK.value
+      when Command::PREPARE_WRITE.value
+      when Command::SET_BANK.value
+      else puts "Unsupported command #{hex_str value}"
+      end
+    end
+    puts "  #{@state}"
+    @sram[index] = value
+  end
+end

src/crab/gba.cr

@@ -3,6 +3,7 @@ require "./reg"
 require "./util"
 require "./scheduler"
 require "./cartridge"
+require "./flash"
 require "./mmio"
 require "./timer"
 require "./keypad"
@@ -18,6 +19,7 @@ require "./debugger"
 class GBA
   getter! scheduler : Scheduler
   getter! cartridge : Cartridge
+  getter! flash : Flash
   getter! mmio : MMIO
   getter! timer : Timer
   getter! keypad : Keypad
@@ -33,6 +35,7 @@ class GBA
   def initialize(@bios_path : String, rom_path : String)
     @scheduler = Scheduler.new
     @cartridge = Cartridge.new rom_path
+    @flash = Flash.new rom_path
     handle_events
 
     SDL.init(SDL::Init::VIDEO | SDL::Init::AUDIO | SDL::Init::JOYSTICK)