input - Add first implementation for joypad class

handling the Joypad register

Makeconf

@@ -20,6 +20,7 @@ modules_libemu.a := memory/device.o \
                     cartridge/cartridge.o \
                     lcd/lcd.o \
                     lcd/palette.o \
+                    input/joypad.o \
 
 modules_vgbc := main.o libemu.a
 verb_vgbc := link

input/joypad.cpp

@@ -0,0 +1,64 @@
+#include <input/joypad.h>
+
+Joypad::Joypad(Cpu& cpu)
+  : cpu(cpu), action_select(false),
+    direction_select(false),
+    keystates{false}
+{}
+
+void Joypad::setKeyState(Key k, bool pressed)
+{
+  bool prevState = keystates[k];
+  keystates[k] = pressed;
+
+  if(!pressed || prevState == pressed)
+    return;
+
+  switch(k)
+    {
+    case A:
+    case B:
+    case Select:
+    case Start:
+      if (action_select)
+        cpu.signalInterrupt(INT_Joypad);
+      break;
+    case Right:
+    case Left:
+    case Up:
+    case Down:
+      if (direction_select)
+        cpu.signalInterrupt(INT_Joypad);
+      break;
+    }
+}
+
+void Joypad::write8(u16 /*addr*/, u8 data)
+{
+  action_select = !(data & P1ActionSelect);
+  direction_select = !(data & P1DirectionSelect);
+}
+
+u8 Joypad::read8(u16 /*addr*/)
+{
+  u8 val = 0x0F;
+
+  if(action_select)
+    val &=
+      (keystates[Start] ? 0 : P1Start) |
+      (keystates[Select] ? 0 : P1Select) |
+      (keystates[B] ? 0 : P1B) |
+      (keystates[A] ? 0 : P1A);
+
+  if(direction_select)
+    val &=
+      (keystates[Down] ? 0 : P1Down) |
+      (keystates[Up] ? 0 : P1Up) |
+      (keystates[Left] ? 0 : P1Left) |
+      (keystates[Right] ? 0 : P1Right);
+
+  val |= (action_select ? 0 : P1ActionSelect);
+  val |= (direction_select ? 0 : P1DirectionSelect);
+
+  return val;
+}

input/joypad.h

@@ -0,0 +1,40 @@
+#pragma once
+
+#include <memory/device.h>
+#include <cpu/cpu.h>
+
+class Joypad : public Mem_device {
+public:
+  enum Key {
+    A,B,Select,Start,
+    Right,Left,Up,Down,
+  };
+
+private:
+  Cpu& cpu;
+
+  bool keystates[8];
+  bool action_select;
+  bool direction_select;
+
+  enum P1Reg {
+    P1ActionSelect    = 0b00100000,
+    P1DirectionSelect = 0b00010000,
+    P1Down            = 0b00001000,
+    P1Start           = 0b00001000,
+    P1Up              = 0b00000100,
+    P1Select          = 0b00000100,
+    P1Left            = 0b00000010,
+    P1B               = 0b00000010,
+    P1Right           = 0b00000001,
+    P1A               = 0b00000001,
+  };
+
+public:
+  Joypad(Cpu& cpu);
+
+  void setKeyState(Key k, bool pressed);
+
+  virtual void write8(u16 addr, u8 data);
+  virtual u8 read8(u16 addr);
+};