wip: dmc

src/apu/channels/dmc.rs

@@ -0,0 +1,70 @@
+use crate::{
+    apu::frame_counter::{ClockFrame, Frame},
+    utils::{BitFlag, Clock},
+};
+
+use super::common::{Channel, Timer};
+
+const RATES: [u16; 16] = [
+    428, 380, 340, 320, 286, 254, 226, 214, 190, 160, 142, 128, 106, 84, 72, 54,
+];
+
+#[derive(Debug, Default)]
+pub struct Dmc {
+    irq_flag: bool,
+    loop_flag: bool,
+    output_level: u8,
+    sample_rate: u16,
+    sample_address: u16,
+    sample_length: u16,
+    sample_buffer: Option<u8>,
+    remaining_bytes: u16,
+    timer: Timer,
+}
+
+impl Dmc {
+    pub fn irq(&self) -> bool {
+        self.irq_flag
+    }
+}
+
+impl Channel for Dmc {
+    fn write_register(&mut self, address: u16, value: u8) {
+        match address % 4 {
+            0 => {
+                self.irq_flag = value.contains(7);
+                self.loop_flag = value.contains(6);
+                self.sample_rate = RATES[value.get_range(0..4) as usize];
+            }
+            1 => self.output_level = value.get_range(0..7),
+            2 => self.sample_address = 0xC00 + (64 * value as u16),
+            _ => self.sample_length = (16 * value as u16) + 1,
+        }
+    }
+
+    fn raw_sample(&self) -> u8 {
+        todo!()
+    }
+
+    fn is_active(&self) -> bool {
+        self.remaining_bytes > 0
+    }
+
+    fn is_mute(&self) -> bool {
+        todo!()
+    }
+
+    fn set_enabled(&mut self, value: bool) {
+        todo!()
+    }
+}
+
+impl Clock for Dmc {
+    fn tick(&mut self) {}
+}
+
+impl ClockFrame for Dmc {
+    fn tick_frame(&mut self, frame: &Frame) {
+        todo!()
+    }
+}

src/apu/channels/mod.rs

@@ -1,9 +1,11 @@
 mod common;
+mod dmc;
 mod noise;
 mod pulse;
 mod triangle;
 
 pub use common::Channel;
+pub use dmc::Dmc;
 pub use noise::Noise;
 pub use pulse::Pulse;
 pub use triangle::Triangle;

src/apu/mod.rs

@@ -3,7 +3,7 @@
 mod channels;
 mod frame_counter;
 
-use channels::{Channel, Noise, Pulse, Triangle};
+use channels::{Channel, Dmc, Noise, Pulse, Triangle};
 use frame_counter::{ClockFrame, FrameCounter};
 
 use crate::{
@@ -17,9 +17,9 @@ mod status_flag {
     pub const P2: u8 = 1;
     pub const T : u8 = 2;
     pub const N : u8 = 3;
-    //pub const D : u8 = 4;
+    pub const D : u8 = 4;
     pub const F : u8 = 6;
-    //pub const I : u8 = 7;
+    pub const I : u8 = 7;
 }
 
 #[derive(Debug, Default)]
@@ -28,6 +28,7 @@ pub struct Apu {
     pulse2: Pulse,
     triangle: Triangle,
     noise: Noise,
+    dmc: Dmc,
     frame_counter: FrameCounter,
     cycle: u64,
     buffer: Vec<f32>,
@@ -49,7 +50,9 @@ impl Apu {
             | (self.pulse2.is_active() as u8) << status_flag::P2
             | (self.triangle.is_active() as u8) << status_flag::T
             | (self.noise.is_active() as u8) << status_flag::N
-            | (self.frame_counter.irq() as u8) << status_flag::F;
+            | (self.dmc.is_active() as u8) << status_flag::D
+            | (self.frame_counter.irq() as u8) << status_flag::F
+            | (self.dmc.irq() as u8) << status_flag::I;
 
         self.frame_counter.clear_interrupt();
 
@@ -72,11 +75,16 @@ impl Apu {
         self.noise.write_register(address, value);
     }
 
+    pub fn write_dmc(&mut self, address: u16, value: u8) {
+        self.dmc.write_register(address, value);
+    }
+
     pub fn write_status(&mut self, value: u8) {
         self.pulse1.set_enabled(value.contains(status_flag::P1));
         self.pulse2.set_enabled(value.contains(status_flag::P2));
         self.triangle.set_enabled(value.contains(status_flag::T));
         self.noise.set_enabled(value.contains(status_flag::N));
+        self.dmc.set_enabled(value.contains(status_flag::D));
     }
 
     pub fn write_frame_counter(&mut self, value: u8) {
@@ -126,6 +134,7 @@ impl Clock for Apu {
             self.noise.tick_frame(&frame);
         }
 
+        // FIXME: find a better sampling strategy
         // 44_100 / 60 == 735 samples/frame
         // 29970 (CPU cycle) / 735 == 40 cycles/frame
         if self.cycle % 40 == 0 {

src/bus/mod.rs

@@ -141,7 +141,7 @@ impl Bus for MainBus {
             0x4004..=0x4007 => self.apu.borrow_mut().write_pulse2(address, value),
             0x4008..=0x400B => self.apu.borrow_mut().write_triangle(address, value),
             0x400C..=0x400F => self.apu.borrow_mut().write_noise(address, value),
-            0x4010..=0x4013 => {} // TODO: DMC
+            0x4010..=0x4013 => self.apu.borrow_mut().write_dmc(address, value),
             0x4015 => self.apu.borrow_mut().write_status(value),
             0x4017 => self.apu.borrow_mut().write_frame_counter(value),
             0x4014 => self.setup_oam_dma(value),