scheduler, ppu vcount/dispstat on scheduler, ppu io fix read/write order

src/crab/gba.cr

@@ -1,5 +1,6 @@
 require "./types"
 require "./util"
+require "./scheduler"
 require "./cartridge"
 require "./mmio"
 require "./bus"
@@ -9,6 +10,7 @@ require "./display"
 require "./ppu"
 
 class GBA
+  getter scheduler : Scheduler
   getter cartridge : Cartridge
   getter mmio : MMIO { MMIO.new self }
   getter bus : Bus { Bus.new self }
@@ -17,10 +19,10 @@ class GBA
   getter display : Display { Display.new }
   getter ppu : PPU { PPU.new self }
 
-  @cycles = 0
-
   def initialize(rom_path : String)
+    @scheduler = Scheduler.new
     @cartridge = Cartridge.new rom_path
+    handle_events
 
     SDL.init(SDL::Init::VIDEO | SDL::Init::AUDIO | SDL::Init::JOYSTICK)
     LibSDL.joystick_open 0
@@ -28,6 +30,7 @@ class GBA
   end
 
   def handle_events : Nil
+    @scheduler.schedule PPU::REFRESH, ->handle_events
     while event = SDL::Event.poll
       case event
       when SDL::Event::Quit then exit 0
@@ -46,11 +49,6 @@ class GBA
   end
 
   def tick(cycles : Int) : Nil
-    ppu.tick cycles
-    @cycles += cycles
-    if @cycles >= PPU::REFRESH
-      handle_events
-      @cycles -= PPU::REFRESH
-    end
+    @scheduler.tick cycles
   end
 end

src/crab/interrupts.cr

@@ -5,10 +5,10 @@ class Interrupts
 
   def read_io(io_addr : Int) : Byte
     case io_addr
-    when 0x200 then (@reg_ie >> 8).to_u8
-    when 0x201 then @reg_ie.to_u8!
-    when 0x202 then (@reg_if >> 8).to_u8
-    when 0x203 then @reg_if.to_u8!
+    when 0x200 then 0xFF_u8 & @reg_ie
+    when 0x201 then 0xFF_u8 & @reg_ie >> 8
+    when 0x202 then 0xFF_u8 & @reg_if
+    when 0x203 then 0xFF_u8 & @reg_if >> 8
     when 0x208 then @reg_ime ? 1_u8 : 0_u8
     when 0x209 then @reg_ime ? 1_u8 : 0_u8
     else            raise "Unimplemented interrupts read ~ addr:#{hex_str io_addr.to_u8}"
@@ -17,10 +17,10 @@ class Interrupts
 
   def write_io(io_addr : Int, value : Byte) : Nil
     case io_addr
-    when 0x200 then @reg_ie = (@reg_ie & 0x00FF) | value.to_u16 << 8
-    when 0x201 then @reg_ie = (@reg_ie & 0xFF00) | value
-    when 0x202 then @reg_ie = (@reg_if & 0x00FF) | value.to_u16 << 8
-    when 0x203 then @reg_ie = (@reg_if & 0xFF00) | value
+    when 0x200 then @reg_ie = (@reg_ie & 0xFF00) | value
+    when 0x201 then @reg_ie = (@reg_ie & 0x00FF) | value.to_u16 << 8
+    when 0x202 then @reg_ie = (@reg_if & 0xFF00) | value
+    when 0x203 then @reg_ie = (@reg_if & 0x00FF) | value.to_u16 << 8
     when 0x208 then @reg_ime = bit?(value, 0)
     when 0x209 then @reg_ime = bit?(value, 0)
     else            raise "Unimplemented interrupts write ~ addr:#{hex_str io_addr.to_u8!}, val:#{value}"

src/crab/ppu.cr

@@ -41,38 +41,61 @@ class PPU
 
   getter dispcnt : DISPCNT = DISPCNT.new 0
   getter dispstat : DISPSTAT = DISPSTAT.new 0
-
-  @cycles = 0
+  getter vcount : UInt16 = 0x0000_u16
 
   def initialize(@gba : GBA)
+    start_scanline
   end
 
-  def tick(cycles : Int) : Nil
-    @cycles += cycles
-    if @cycles >= REFRESH
+  def start_scanline : Nil
+    @gba.scheduler.schedule 960, ->start_hblank
+  end
+
+  def start_hblank : Nil
+    @gba.scheduler.schedule 272, ->end_hblank
+    @dispstat.hblank = true
+  end
+
+  def end_hblank : Nil
+    @dispstat.hblank = false
+    @vcount += 1
+    if @vcount == 228
+      @vcount = 0
+      @dispstat.vblank = false
+      @gba.scheduler.schedule 0, ->start_scanline
+    elsif @vcount == 160
+      @dispstat.vblank = true
+      @gba.scheduler.schedule 0, ->start_vblank_line
       @gba.display.draw @vram
-      @cycles -= REFRESH
+    elsif @vcount >= 160
+      @gba.scheduler.schedule 0, ->start_vblank_line
+    else
+      @gba.scheduler.schedule 0, ->start_scanline
     end
   end
 
+  def start_vblank_line : Nil
+    @gba.scheduler.schedule 960, ->start_hblank
+  end
+
   def read_io(io_addr : Int) : Byte
     case io_addr
-    when 0x000 then 0xFF_u8 & @dispcnt.value >> 8
-    when 0x001 then 0xFF_u8 & @dispcnt.value
-    when 0x004 then 0xFF_u8 & @dispstat.value >> 8
-    when 0x005 then 0xFF_u8 & @dispstat.value
+    when 0x000 then 0xFF_u8 & @dispcnt.value
+    when 0x001 then 0xFF_u8 & @dispcnt.value >> 8
+    when 0x004 then 0xFF_u8 & @dispstat.value
+    when 0x005 then 0xFF_u8 & @dispstat.value >> 8
     else            raise "Unimplemented PPU read ~ addr:#{hex_str io_addr.to_u8}"
     end
   end
 
   def write_io(io_addr : Int, value : Byte) : Nil
     case io_addr
-    when 0x000 then @dispcnt.value = (@dispcnt.value & 0x00FF) | value.to_u16 << 8
-    when 0x001 then @dispcnt.value = (@dispcnt.value & 0xFF00) | value
+    when 0x000 then @dispcnt.value = (@dispcnt.value & 0xFF00) | value
+    when 0x001 then @dispcnt.value = (@dispcnt.value & 0x00FF) | value.to_u16 << 8
     when 0x002 # undocumented - green swap
     when 0x003 # undocumented - green swap
-    when 0x004 then @dispstat.value = (@dispstat.value & 0x00FF) | value.to_u16 << 8
-    when 0x005 then @dispstat.value = (@dispstat.value & 0xFF00) | value
+    when 0x004 then @dispstat.value = (@dispstat.value & 0xFF00) | value
+    when 0x005 then @dispstat.value = (@dispstat.value & 0x00FF) | value.to_u16 << 8
     else            raise "Unimplemented PPU write ~ addr:#{hex_str io_addr.to_u8}, val:#{value}"
     end
   end

src/crab/scheduler.cr

@@ -0,0 +1,43 @@
+class Scheduler
+  private record Event, cycles : UInt64, proc : Proc(Void)
+
+  @events : Deque(Event) = Deque(Event).new 10
+  @cycles : UInt64 = 0
+
+  def schedule(cycles : Int, proc : Proc(Void)) : Nil
+    self << Event.new @cycles + cycles, proc
+  end
+
+  def schedule(cycles : Int, &block : ->)
+    self << Event.new @cycles + cycles, block
+  end
+
+  @[AlwaysInline]
+  def <<(event : Event) : Nil
+    idx = @events.bsearch_index { |e| e.cycles > event.cycles }
+    unless idx.nil?
+      @events.insert(idx, event)
+    else
+      @events << event
+    end
+  end
+
+  def tick(cycles : Int) : Nil
+    cycles.times do
+      @cycles += 1
+      call_current
+    end
+  end
+
+  def call_current : Nil
+    loop do
+      event = @events.first?
+      if event && @cycles >= event.cycles
+        event.proc.call
+        @events.shift
+      else
+        break
+      end
+    end
+  end
+end