Merge pull request #132 from gwilymk/add-timer-support

Add first-class timer support

agb/examples/mixer_basic.rs

@@ -17,7 +17,8 @@ fn main() -> ! {
     let mut input = ButtonController::new();
     let vblank_provider = agb::interrupt::VBlank::get();
 
-    let mut mixer = gba.mixer.mixer();
+    let mut timers = gba.timers.timers();
+    let mut mixer = gba.mixer.mixer(&mut timers.timer0);
     mixer.enable();
 
     let channel = SoundChannel::new(DEAD_CODE);

agb/examples/stereo_sound.rs

@@ -14,15 +14,35 @@ fn main() -> ! {
     let mut gba = Gba::new();
     let vblank_provider = agb::interrupt::VBlank::get();
 
-    let mut mixer = gba.mixer.mixer();
+    let mut timer_controller = gba.timers.timers();
+    let mut timer = timer_controller.timer1;
+    timer.set_enabled(true);
+
+    let mut mixer = gba.mixer.mixer(&mut timer_controller.timer0);
     mixer.enable();
 
     let mut channel = SoundChannel::new(LET_IT_IN);
     channel.stereo();
     mixer.play_sound(channel).unwrap();
 
+    let mut frame_counter = 0i32;
     loop {
         vblank_provider.wait_for_vblank();
+        let before_mixing_cycles = timer.get_value();
         mixer.vblank();
+        let after_mixing_cycles = timer.get_value();
+
+        frame_counter = frame_counter.wrapping_add(1);
+
+        if frame_counter % 128 == 0 {
+            let total_cycles = after_mixing_cycles.wrapping_sub(before_mixing_cycles) as u32;
+
+            let percent = (total_cycles * 100) / 280896;
+            agb::println!(
+                "Took {} cycles to calculate mixer ~= {}% of total frame",
+                total_cycles,
+                percent
+            );
+        }
     }
 }

agb/src/lib.rs

@@ -39,6 +39,8 @@ mod single;
 pub mod sound;
 /// System BIOS calls / syscalls.
 pub mod syscall;
+/// Interactions with the internal timers
+pub mod timer;
 
 #[cfg(not(test))]
 use core::fmt::Write;
@@ -61,6 +63,7 @@ pub struct Gba {
     pub display: display::Display,
     pub sound: sound::dmg::Sound,
     pub mixer: sound::mixer::MixerController,
+    pub timers: timer::TimerController,
 }
 
 impl Gba {
@@ -73,6 +76,7 @@ impl Gba {
             display: display::Display::new(),
             sound: sound::dmg::Sound::new(),
             mixer: sound::mixer::MixerController::new(),
+            timers: timer::TimerController::new(),
         }
     }
 }
@@ -169,6 +173,12 @@ mod test {
         assert_eq!(1, 1);
     }
 
+    #[test_case]
+    fn gba_struct_is_zero_sized(_gba: &mut Gba) {
+        use core::mem;
+        assert_eq!(mem::size_of::<Gba>(), 0);
+    }
+
     #[test_case]
     fn wait_30_frames(_gba: &mut Gba) {
         let vblank = crate::interrupt::VBlank::get();

agb/src/sound/mixer/hw.rs

@@ -1,4 +1,5 @@
 use crate::memory_mapped::MemoryMapped;
+use crate::timer::Timer;
 
 const fn dma_source_addr(dma: usize) -> usize {
     0x0400_00b0 + 0x0c * dma
@@ -24,10 +25,6 @@ const DMA2_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(dma_control_a
 const FIFOA_DEST_ADDR: u32 = 0x0400_00a0;
 const FIFOB_DEST_ADDR: u32 = 0x0400_00a4;
 
-// Similarly for proper timer support
-const TIMER0_COUNTER: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0100) };
-const TIMER0_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0102) };
-
 const SOUND_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0082) };
 const SOUND_CONTROL_X: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0084) };
 
@@ -94,9 +91,7 @@ pub(super) fn set_sound_control_register_for_mixer() {
     SOUND_CONTROL_X.set(1 << 7);
 }
 
-pub(super) fn set_timer_counter_for_frequency_and_enable(frequency: i32) {
-    let counter = 65536 - (16777216 / frequency);
-    TIMER0_COUNTER.set(counter as u16);
-
-    TIMER0_CONTROL.set(1 << 7); // enable the timer
+pub(super) fn set_timer_counter_for_frequency_and_enable(timer: &mut Timer, frequency: i32) {
+    timer.set_overflow_amount((16777216 / frequency) as u16);
+    timer.set_enabled(true);
 }

agb/src/sound/mixer/mod.rs

@@ -5,6 +5,7 @@ pub use sw_mixer::ChannelId;
 pub use sw_mixer::Mixer;
 
 use crate::number::Num;
+use crate::timer::Timer;
 
 #[non_exhaustive]
 pub struct MixerController {}
@@ -14,8 +15,8 @@ impl MixerController {
         MixerController {}
     }
 
-    pub fn mixer(&mut self) -> Mixer {
-        Mixer::new()
+    pub fn mixer<'a>(&mut self, timer: &'a mut Timer) -> Mixer<'a> {
+        Mixer::new(timer)
     }
 }
 

agb/src/sound/mixer/sw_mixer.rs

@@ -2,6 +2,7 @@ use super::hw;
 use super::hw::LeftOrRight;
 use super::{SoundChannel, SoundPriority};
 use crate::number::Num;
+use crate::timer::Timer;
 
 // Defined in mixer.s
 extern "C" {
@@ -18,25 +19,29 @@ extern "C" {
     fn agb_rs__mixer_collapse(sound_buffer: *mut i8, input_buffer: *const Num<i16, 4>);
 }
 
-pub struct Mixer {
+pub struct Mixer<'a> {
     buffer: MixerBuffer,
     channels: [Option<SoundChannel>; 8],
     indices: [i32; 8],
+
+    timer: &'a mut Timer,
 }
 
 pub struct ChannelId(usize, i32);
 
-impl Mixer {
-    pub(super) fn new() -> Self {
+impl<'a> Mixer<'a> {
+    pub(super) fn new(timer: &'a mut Timer) -> Self {
         Mixer {
             buffer: MixerBuffer::new(),
             channels: Default::default(),
             indices: Default::default(),
+
+            timer,
         }
     }
 
-    pub fn enable(&self) {
-        hw::set_timer_counter_for_frequency_and_enable(SOUND_FREQUENCY);
+    pub fn enable(&mut self) {
+        hw::set_timer_counter_for_frequency_and_enable(self.timer, SOUND_FREQUENCY);
         hw::set_sound_control_register_for_mixer();
     }
 

agb/src/timer.rs

@@ -0,0 +1,117 @@
+use crate::memory_mapped::MemoryMapped;
+
+const fn timer_data(timer: usize) -> MemoryMapped<u16> {
+    unsafe { MemoryMapped::new(0x0400_0100 + 4 * timer) }
+}
+
+const fn timer_control(timer: usize) -> MemoryMapped<u16> {
+    unsafe { MemoryMapped::new(0x0400_0102 + 4 * timer) }
+}
+
+#[derive(Clone, Copy)]
+pub enum Divider {
+    // 16.78MHz or 59.59ns
+    Divider1,
+    // 262.21kHz or 3.815us
+    Divider64,
+    // 65.536kHz or 15.26us
+    Divider256,
+    // 16.384kHz or 61.04us
+    Divider1024,
+}
+
+impl Divider {
+    fn get_as_bits(&self) -> u16 {
+        use Divider::*;
+
+        match self {
+            Divider1 => 0,
+            Divider64 => 1,
+            Divider256 => 2,
+            Divider1024 => 3,
+        }
+    }
+}
+
+#[non_exhaustive]
+pub struct Timer {
+    timer_number: u16,
+}
+
+#[non_exhaustive]
+pub struct Timers {
+    pub timer0: Timer,
+    pub timer1: Timer,
+    pub timer2: Timer,
+    pub timer3: Timer,
+}
+
+impl Timers {
+    pub(crate) unsafe fn new() -> Self {
+        Self {
+            timer0: Timer::new(0),
+            timer1: Timer::new(1),
+            timer2: Timer::new(2),
+            timer3: Timer::new(3),
+        }
+    }
+}
+
+impl Timer {
+    unsafe fn new(timer_number: u16) -> Self {
+        let new_timer = Self { timer_number };
+        new_timer.data_register().set(0);
+        new_timer.control_register().set(0);
+
+        new_timer
+    }
+
+    pub fn set_overflow_amount(&mut self, n: u16) {
+        let count_up_value = 0u16.wrapping_sub(n);
+        self.data_register().set(count_up_value);
+    }
+
+    pub fn get_value(&self) -> u16 {
+        self.data_register().get()
+    }
+
+    pub fn set_divider(&mut self, divider: Divider) {
+        self.control_register()
+            .set_bits(divider.get_as_bits(), 2, 0);
+    }
+
+    pub fn set_enabled(&mut self, enabled: bool) {
+        let bit = if enabled { 1 } else { 0 };
+        self.control_register().set_bits(bit, 1, 7);
+    }
+
+    pub fn set_cascade(&mut self, cascade: bool) {
+        let bit = if cascade { 1 } else { 0 };
+        self.control_register().set_bits(bit, 1, 2);
+    }
+
+    fn data_register(&self) -> MemoryMapped<u16> {
+        timer_data(self.get_timer_number())
+    }
+
+    fn control_register(&self) -> MemoryMapped<u16> {
+        timer_control(self.get_timer_number())
+    }
+
+    fn get_timer_number(&self) -> usize {
+        self.timer_number as usize
+    }
+}
+
+#[non_exhaustive]
+pub struct TimerController {}
+
+impl TimerController {
+    pub(crate) const fn new() -> Self {
+        Self {}
+    }
+
+    pub fn timers(&mut self) -> Timers {
+        unsafe { Timers::new() }
+    }
+}