From 6f84b116a6f52c0611f18994b011a0339abb6310 Mon Sep 17 00:00:00 2001
From: Determinant <ted.sybil@gmail.com>
Date: Thu, 16 Nov 2017 12:11:53 -0500
Subject: ...

---
 src/controller.rs | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/ppu.rs        | 30 ++++++++++++++++++----------
 2 files changed, 79 insertions(+), 10 deletions(-)
 create mode 100644 src/controller.rs

diff --git a/src/controller.rs b/src/controller.rs
new file mode 100644
index 0000000..cc01d0f
--- /dev/null
+++ b/src/controller.rs
@@ -0,0 +1,59 @@
+
+pub trait Controller {
+    fn read(&self) -> u8;
+    fn write(&self, data: u8);
+}
+
+pub mod stdctl {
+    use core::cell::Cell;
+    use controller::Controller;
+    #[derive(Copy, Clone)]
+    pub enum Button {
+        A = 0,
+        B = 1,
+        Select = 2,
+        Start = 3,
+        Up = 4,
+        Down = 5,
+        Left = 6,
+        Right = 7,
+        Null = 8,
+    }
+    pub struct Joystick {
+        strobe: Cell<bool>,
+        reg: Cell<u8>,
+        back_reg: Cell<u8>
+    }
+
+    impl Joystick {
+        pub fn new() -> Self {
+            Joystick{reg: Cell::new(0), strobe: Cell::new(false), back_reg: Cell::new(0)}
+        }
+
+        pub fn set(&self, buttons: &[bool]) {
+            let mut reg = 0;
+            for (i, v) in buttons.iter().enumerate() {
+                if *v {
+                    reg |= 1 << i;
+                }
+            }
+            self.reg.set(reg);
+            self.back_reg.set(reg);
+        }
+    }
+
+    impl Controller for Joystick {
+        fn read(&self) -> u8 {
+            let res = self.reg.get() & 1;
+            if !self.strobe.get() {
+                self.reg.set(self.reg.get() >> 1);
+            }
+            res
+        }
+        
+        fn write(&self, data: u8) {
+            self.strobe.set(data & 1 == 1);
+            self.reg.set(self.back_reg.get());
+        }
+    }
+}
diff --git a/src/ppu.rs b/src/ppu.rs
index ad9c991..62a8261 100644
--- a/src/ppu.rs
+++ b/src/ppu.rs
@@ -32,11 +32,12 @@ pub struct PPU<'a> {
     v: u16, /* current vram addr */
     t: u16, /* temporary vram addr */
     w: bool, /* first/second write toggle */
+    f: bool, /* if it is an odd frame */
     cycle: u16, /* cycle in the current scanline */
     /* rendering regs & latches */
-        /* background registers */
+        /* background register (current two tiles) */
     bg_pixel: u64,
-        /* background latches */
+        /* background latches for next tile */
     bg_nt: u8,
     bg_attr: u8,
     bg_bit_low: u8,
@@ -178,9 +179,11 @@ impl<'a> PPU<'a> {
                 self.oamaddr = self.oamaddr.wrapping_add(1);
             }
         }
+        /*
         cpu.cycle += 1;
         cpu.cycle += cpu.cycle & 1;
         cpu.cycle += 512;
+        */
     }
 
     #[inline(always)] fn get_spritesize(&self) -> u8 {(self.ppuctl >> 5) & 1}
@@ -443,7 +446,6 @@ impl<'a> PPU<'a> {
         let ppumask = 0x00;
         let ppustatus = 0xa0;
         let oamaddr = 0x00;
-        let w = false;
         let buffered_read = 0x00;
         let cycle = 370;
         let scanline = 240;
@@ -454,7 +456,7 @@ impl<'a> PPU<'a> {
             ppustatus,
             oamaddr,
             reg: 0,
-            x: 0, v: 0, t: 0, w, cycle,
+            x: 0, v: 0, t: 0, w: false, f: true, cycle,
             bg_pixel: 0,
             bg_nt: 0, bg_attr: 0,
             bg_bit_low: 0, bg_bit_high: 0,
@@ -483,7 +485,7 @@ impl<'a> PPU<'a> {
     pub fn tick(&mut self) -> bool {
         let cycle = self.cycle;
         if cycle == 0 {
-            self.cycle = cycle + 1;
+            self.cycle = 1;
             return false;
         }
         let rendering = self.get_show_bg() || self.get_show_sp();
@@ -526,11 +528,18 @@ impl<'a> PPU<'a> {
                     self.reset_cx();
                     self.fetch_sprite();
                 }
-                if pre_line && cycle == 1 {
-                    /* clear vblank, sprite zero hit & overflow */
-                    self.ppustatus &= !(PPU::FLAG_VBLANK |
-                                        PPU::FLAG_SPRITE_ZERO | PPU::FLAG_OVERFLOW);
-                    self.bg_pixel = 0;
+                if pre_line {
+                    if cycle == 1 {
+                        /* clear vblank, sprite zero hit & overflow */
+                        self.ppustatus &= !(PPU::FLAG_VBLANK |
+                                            PPU::FLAG_SPRITE_ZERO | PPU::FLAG_OVERFLOW);
+                        self.bg_pixel = 0
+                    } else if cycle == 339 && self.f {
+                        self.scanline = 0;
+                        self.cycle = 0;
+                        self.f = !self.f;
+                        return false;
+                    }
                 }
             }
         } else {
@@ -551,6 +560,7 @@ impl<'a> PPU<'a> {
             self.scanline += 1;
             if self.scanline > 261 {
                 self.scanline = 0;
+                self.f = !self.f;
             }
         }
         false
-- 
cgit v1.2.3-70-g09d2