Merge pull request #60 from gwilymk/actual-sound-mixing

Actual sound mixing

agb/examples/beep.rs

@@ -11,25 +11,29 @@ pub fn main() -> ! {
 
     gba.sound.enable();
 
-    let sweep_settings = sound::SweepSettings::default();
+    let sweep_settings = sound::dmg::SweepSettings::default();
     gba.sound.channel1().play_sound(
         1024,
         Some(0),
         &sweep_settings,
-        &sound::EnvelopeSettings::default(),
-        sound::DutyCycle::Half,
+        &sound::dmg::EnvelopeSettings::default(),
+        sound::dmg::DutyCycle::Half,
     );
 
     gba.sound.channel2().play_sound(
         1524,
         Some(0),
-        &sound::EnvelopeSettings::default(),
-        sound::DutyCycle::Half,
+        &sound::dmg::EnvelopeSettings::default(),
+        sound::dmg::DutyCycle::Half,
     );
 
-    gba.sound
-        .noise()
-        .play_sound(Some(0), &sound::EnvelopeSettings::default(), 4, false, 1);
+    gba.sound.noise().play_sound(
+        Some(0),
+        &sound::dmg::EnvelopeSettings::default(),
+        4,
+        false,
+        1,
+    );
 
     loop {}
 }

agb/examples/mixer_basic.rs

@@ -0,0 +1,27 @@
+#![no_std]
+#![no_main]
+
+extern crate agb;
+
+use agb::sound::mixer::SoundChannel;
+use agb::Gba;
+
+// Music - "I will not let you let me down" by Josh Woodward, free download at http://joshwoodward.com
+const I_WILL_NOT_LET_YOU_LET_ME_DOWN: &[u8] = include_bytes!("i-will-not-let-you-let-me-down.raw");
+
+#[no_mangle]
+pub fn main() -> ! {
+    let mut gba = Gba::new();
+    let vblank_provider = gba.display.vblank.get();
+
+    let mut mixer = gba.mixer.mixer();
+    mixer.enable();
+
+    let channel = SoundChannel::new(I_WILL_NOT_LET_YOU_LET_ME_DOWN);
+    mixer.play_sound(channel);
+
+    loop {
+        vblank_provider.wait_for_VBlank();
+        mixer.vblank();
+    }
+}

agb/src/lib.rs

@@ -50,7 +50,8 @@ static mut GBASINGLE: single::Singleton<Gba> = single::Singleton::new(unsafe { G
 
 pub struct Gba {
     pub display: display::Display,
-    pub sound: sound::Sound,
+    pub sound: sound::dmg::Sound,
+    pub mixer: sound::mixer::MixerController,
 }
 
 impl Gba {
@@ -61,7 +62,8 @@ impl Gba {
     const unsafe fn single_new() -> Self {
         Self {
             display: display::Display::new(),
-            sound: sound::Sound::new(),
+            sound: sound::dmg::Sound::new(),
+            mixer: sound::mixer::MixerController::new(),
         }
     }
 }

agb/src/sound/dmg.rs

@@ -0,0 +1,238 @@
+use crate::memory_mapped::MemoryMapped;
+
+const CHANNEL_1_SWEEP: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0060) };
+const CHANNEL_1_LENGTH_DUTY_ENVELOPE: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0062) };
+const CHANNEL_1_FREQUENCY_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0064) };
+
+const CHANNEL_2_LENGTH_DUTY_ENVELOPE: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0068) };
+const CHANNEL_2_FREQUENCY_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_006c) };
+
+const CHANNEL_4_LENGTH_ENVELOPE: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0078) };
+const CHANNEL_4_FREQUENCY_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_007c) };
+
+const MASTER_SOUND_VOLUME_ENABLE: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0080) };
+const MASTER_SOUND_VOLUME_MIXING: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0082) };
+const MASTER_SOUND_STATUS: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0084) };
+
+#[non_exhaustive]
+pub struct Sound {}
+
+impl Sound {
+    pub(crate) const unsafe fn new() -> Self {
+        Sound {}
+    }
+
+    pub fn channel1(&self) -> Channel1 {
+        Channel1 {}
+    }
+
+    pub fn channel2(&self) -> Channel2 {
+        Channel2 {}
+    }
+
+    pub fn noise(&self) -> Noise {
+        Noise {}
+    }
+
+    pub fn enable(&self) {
+        MASTER_SOUND_STATUS.set_bits(1, 1, 7);
+
+        #[allow(clippy::unusual_byte_groupings)] // I've split these like this for a reason
+        MASTER_SOUND_VOLUME_ENABLE.set(0b1111_1111_0_111_0_111);
+        MASTER_SOUND_VOLUME_MIXING.set(0b10);
+    }
+}
+
+#[non_exhaustive]
+pub struct Channel1 {}
+
+impl Channel1 {
+    pub fn play_sound(
+        &self,
+        frequency: u16,
+        length: Option<u8>,
+        sweep_settings: &SweepSettings,
+        envelope_settings: &EnvelopeSettings,
+        duty_cycle: DutyCycle,
+    ) {
+        CHANNEL_1_SWEEP.set(sweep_settings.as_bits());
+        let length_bits = length.unwrap_or(0) as u16;
+        assert!(length_bits < 64, "Length must be less than 64");
+
+        let length_flag: u16 = length.map(|_| 1 << 14).unwrap_or(0);
+        let initial: u16 = 1 << 15;
+
+        assert!(frequency < 2048, "Frequency must be less than 2048");
+
+        CHANNEL_1_LENGTH_DUTY_ENVELOPE
+            .set(envelope_settings.as_bits() | duty_cycle.as_bits() | length_bits);
+        CHANNEL_1_FREQUENCY_CONTROL.set(frequency | length_flag | initial);
+    }
+}
+
+#[non_exhaustive]
+pub struct Channel2 {}
+
+impl Channel2 {
+    pub fn play_sound(
+        &self,
+        frequency: u16,
+        length: Option<u8>,
+        envelope_settings: &EnvelopeSettings,
+        duty_cycle: DutyCycle,
+    ) {
+        let length_bits = length.unwrap_or(0) as u16;
+        assert!(length_bits < 64, "Length must be less than 64");
+
+        let length_flag: u16 = length.map(|_| 1 << 14).unwrap_or(0);
+        let initial: u16 = 1 << 15;
+
+        assert!(frequency < 2048, "Frequency must be less than 2048");
+
+        CHANNEL_2_LENGTH_DUTY_ENVELOPE
+            .set(envelope_settings.as_bits() | duty_cycle.as_bits() | length_bits);
+        CHANNEL_2_FREQUENCY_CONTROL.set(frequency | length_flag | initial);
+    }
+}
+
+#[non_exhaustive]
+pub struct Noise {}
+
+impl Noise {
+    pub fn play_sound(
+        &self,
+        length: Option<u8>,
+        envelope_setting: &EnvelopeSettings,
+        frequency_divider: u8,
+        counter_step_width_15: bool,
+        shift_clock_frequency: u8,
+    ) {
+        let length_bits = length.unwrap_or(0) as u16;
+        assert!(length_bits < 64, "length must be less than 16");
+
+        assert!(
+            frequency_divider < 8,
+            "frequency divider must be less than 8"
+        );
+        assert!(
+            shift_clock_frequency < 16,
+            "frequency clock divider must be less than 16"
+        );
+
+        let length_flag: u16 = length.map(|_| 1 << 14).unwrap_or(0);
+        let initial: u16 = 1 << 15;
+
+        let counter_step_bit = if counter_step_width_15 { 0 } else { 1 << 3 };
+
+        CHANNEL_4_LENGTH_ENVELOPE.set(length_bits | envelope_setting.as_bits());
+        CHANNEL_4_FREQUENCY_CONTROL.set(
+            (frequency_divider as u16)
+                | counter_step_bit
+                | ((shift_clock_frequency as u16) << 4)
+                | length_flag
+                | initial,
+        )
+    }
+}
+
+pub enum SoundDirection {
+    Increase,
+    Decrease,
+}
+
+impl SoundDirection {
+    fn as_bits(&self) -> u16 {
+        match &self {
+            SoundDirection::Increase => 1,
+            SoundDirection::Decrease => 0,
+        }
+    }
+}
+
+pub struct SweepSettings {
+    number_of_sweep_shifts: u8,
+    sound_direction: SoundDirection,
+    sweep_time: u8,
+}
+
+impl SweepSettings {
+    pub fn new(
+        number_of_sweep_shifts: u8,
+        sound_direction: SoundDirection,
+        sweep_time: u8,
+    ) -> Self {
+        assert!(
+            number_of_sweep_shifts < 8,
+            "Number of sweep shifts must be less than 8"
+        );
+        assert!(sweep_time < 8, "Sweep time must be less than 8");
+
+        SweepSettings {
+            number_of_sweep_shifts,
+            sound_direction,
+            sweep_time,
+        }
+    }
+
+    fn as_bits(&self) -> u16 {
+        ((self.number_of_sweep_shifts as u16) & 0b111)
+            | ((1 - self.sound_direction.as_bits()) << 3) // sweep works backwards
+            | ((self.sweep_time as u16) & 0b111) << 4
+    }
+}
+
+impl Default for SweepSettings {
+    fn default() -> Self {
+        SweepSettings::new(0, SoundDirection::Increase, 0)
+    }
+}
+
+pub struct EnvelopeSettings {
+    step_time: u8,
+    direction: SoundDirection,
+    initial_volume: u8,
+}
+
+impl EnvelopeSettings {
+    pub fn new(step_time: u8, direction: SoundDirection, initial_volume: u8) -> Self {
+        assert!(step_time < 8, "Step time must be less than 8");
+        assert!(initial_volume < 16, "Initial volume must be less that 16");
+        EnvelopeSettings {
+            step_time,
+            direction,
+            initial_volume,
+        }
+    }
+
+    fn as_bits(&self) -> u16 {
+        (self.step_time as u16) << 8
+            | (self.direction.as_bits() << 11)
+            | ((self.initial_volume as u16) << 12)
+    }
+}
+
+impl Default for EnvelopeSettings {
+    fn default() -> Self {
+        EnvelopeSettings::new(0, SoundDirection::Increase, 15)
+    }
+}
+
+pub enum DutyCycle {
+    OneEighth,
+    OneQuarter,
+    Half,
+    ThreeQuarters,
+}
+
+impl DutyCycle {
+    fn as_bits(&self) -> u16 {
+        use DutyCycle::*;
+
+        match &self {
+            OneEighth => 0,
+            OneQuarter => 1,
+            Half => 2,
+            ThreeQuarters => 3,
+        }
+    }
+}

agb/src/sound/mixer.rs

@@ -0,0 +1,181 @@
+use crate::memory_mapped::MemoryMapped;
+
+#[non_exhaustive]
+pub struct MixerController {}
+
+impl MixerController {
+    pub(crate) const fn new() -> Self {
+        MixerController {}
+    }
+
+    pub fn mixer(&mut self) -> Mixer {
+        Mixer::new()
+    }
+}
+
+pub struct Mixer {
+    buffer: MixerBuffer,
+    channels: [Option<SoundChannel>; 16],
+}
+
+impl Mixer {
+    fn new() -> Self {
+        Mixer {
+            buffer: MixerBuffer::new(),
+            channels: Default::default(),
+        }
+    }
+
+    pub fn enable(&self) {
+        set_timer_counter_for_frequency_and_enable(SOUND_FREQUENCY);
+        set_sound_control_register_for_mixer();
+    }
+
+    pub fn vblank(&mut self) {
+        self.buffer.swap();
+        self.buffer.clear();
+
+        for channel in self.channels.iter_mut() {
+            let mut has_finished = false;
+
+            if let Some(some_channel) = channel {
+                self.buffer.write_channel(some_channel);
+                some_channel.pos += SOUND_BUFFER_SIZE;
+
+                if some_channel.pos >= some_channel.data.len() {
+                    has_finished = true;
+                }
+            }
+
+            if has_finished {
+                channel.take();
+            }
+        }
+    }
+
+    pub fn play_sound(&mut self, new_channel: SoundChannel) {
+        for channel in self.channels.iter_mut() {
+            if channel.is_some() {
+                continue;
+            }
+
+            channel.replace(new_channel);
+            return;
+        }
+
+        panic!("Cannot play more than 16 sounds at once");
+    }
+}
+
+pub struct SoundChannel {
+    data: &'static [u8],
+    pos: usize,
+}
+
+impl SoundChannel {
+    pub fn new(data: &'static [u8]) -> Self {
+        SoundChannel { data, pos: 0 }
+    }
+}
+
+// I've picked one frequency that works nicely. But there are others that work nicely
+// which we may want to consider in the future: https://web.archive.org/web/20070608011909/http://deku.gbadev.org/program/sound1.html
+const SOUND_FREQUENCY: i32 = 10512;
+const SOUND_BUFFER_SIZE: usize = 176;
+
+struct MixerBuffer {
+    buffer1: [i8; SOUND_BUFFER_SIZE],
+    buffer2: [i8; SOUND_BUFFER_SIZE],
+
+    buffer_1_active: bool,
+}
+
+impl MixerBuffer {
+    fn new() -> Self {
+        MixerBuffer {
+            buffer1: [0; SOUND_BUFFER_SIZE],
+            buffer2: [0; SOUND_BUFFER_SIZE],
+
+            buffer_1_active: true,
+        }
+    }
+
+    fn swap(&mut self) {
+        self.buffer_1_active = !self.buffer_1_active;
+
+        if self.buffer_1_active {
+            enable_dma1_for_sound(&self.buffer1);
+        } else {
+            enable_dma1_for_sound(&self.buffer2);
+        }
+    }
+
+    fn clear(&mut self) {
+        self.get_write_buffer().fill(0);
+    }
+
+    fn write_channel(&mut self, channel: &SoundChannel) {
+        let data_to_copy = &channel.data[channel.pos..(channel.pos + SOUND_BUFFER_SIZE)];
+        let place_to_write_to = self.get_write_buffer();
+
+        for (i, v) in data_to_copy.iter().enumerate() {
+            let v = *v as i8;
+            place_to_write_to[i] = place_to_write_to[i].saturating_add(v);
+        }
+    }
+
+    fn get_write_buffer(&mut self) -> &mut [i8; SOUND_BUFFER_SIZE] {
+        if self.buffer_1_active {
+            &mut self.buffer2
+        } else {
+            &mut self.buffer1
+        }
+    }
+}
+
+// Once we have proper DMA support, we should use that rather than hard coding these here too
+const DMA1_SOURCE_ADDR: MemoryMapped<u32> = unsafe { MemoryMapped::new(0x0400_00bc) };
+const DMA1_DEST_ADDR: MemoryMapped<u32> = unsafe { MemoryMapped::new(0x0400_00c0) };
+const _DMA1_WORD_COUNT: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_00c4) }; // sound ignores this for some reason
+const DMA1_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_00c6) };
+
+const FIFOA_DEST_ADDR: u32 = 0x0400_00a0;
+
+// 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) };
+
+fn enable_dma1_for_sound(sound_memory: &[i8]) {
+    let dest_fixed: u16 = 2 << 5; // dest addr control = fixed
+    let repeat: u16 = 1 << 9;
+    let transfer_type: u16 = 1 << 10; // transfer in words
+    let dma_start_timing: u16 = 3 << 12; // sound fifo timing
+    let enable: u16 = 1 << 15; // enable
+
+    DMA1_CONTROL.set(0);
+    DMA1_SOURCE_ADDR.set(sound_memory.as_ptr() as u32);
+    DMA1_DEST_ADDR.set(FIFOA_DEST_ADDR);
+    DMA1_CONTROL.set(dest_fixed | repeat | transfer_type | dma_start_timing | enable);
+}
+
+fn set_sound_control_register_for_mixer() {
+    let sound_a_volume_100: u16 = 1 << 2;
+    let sound_a_rout: u16 = 1 << 8;
+    let sound_a_lout: u16 = 1 << 9;
+    let sound_a_fifo_reset: u16 = 1 << 11;
+
+    SOUND_CONTROL.set(sound_a_volume_100 | sound_a_rout | sound_a_lout | sound_a_fifo_reset);
+
+    // master sound enable
+    SOUND_CONTROL_X.set(1 << 7);
+}
+
+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
+}

agb/src/sound/mod.rs

@@ -1,238 +1,2 @@
-use crate::memory_mapped::MemoryMapped;
-
-const CHANNEL_1_SWEEP: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0060) };
-const CHANNEL_1_LENGTH_DUTY_ENVELOPE: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0062) };
-const CHANNEL_1_FREQUENCY_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0064) };
-
-const CHANNEL_2_LENGTH_DUTY_ENVELOPE: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0068) };
-const CHANNEL_2_FREQUENCY_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_006c) };
-
-const CHANNEL_4_LENGTH_ENVELOPE: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0078) };
-const CHANNEL_4_FREQUENCY_CONTROL: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_007c) };
-
-const MASTER_SOUND_VOLUME_ENABLE: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0080) };
-const MASTER_SOUND_VOLUME_MIXING: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0082) };
-const MASTER_SOUND_STATUS: MemoryMapped<u16> = unsafe { MemoryMapped::new(0x0400_0084) };
-
-#[non_exhaustive]
-pub struct Sound {}
-
-impl Sound {
-    pub(crate) const unsafe fn new() -> Self {
-        Sound {}
-    }
-
-    pub fn channel1(&self) -> Channel1 {
-        Channel1 {}
-    }
-
-    pub fn channel2(&self) -> Channel2 {
-        Channel2 {}
-    }
-
-    pub fn noise(&self) -> Noise {
-        Noise {}
-    }
-
-    pub fn enable(&self) {
-        MASTER_SOUND_STATUS.set_bits(1, 1, 7);
-
-        #[allow(clippy::unusual_byte_groupings)] // I've split these like this for a reason
-        MASTER_SOUND_VOLUME_ENABLE.set(0b1111_1111_0_111_0_111);
-        MASTER_SOUND_VOLUME_MIXING.set(0b10);
-    }
-}
-
-#[non_exhaustive]
-pub struct Channel1 {}
-
-impl Channel1 {
-    pub fn play_sound(
-        &self,
-        frequency: u16,
-        length: Option<u8>,
-        sweep_settings: &SweepSettings,
-        envelope_settings: &EnvelopeSettings,
-        duty_cycle: DutyCycle,
-    ) {
-        CHANNEL_1_SWEEP.set(sweep_settings.as_bits());
-        let length_bits = length.unwrap_or(0) as u16;
-        assert!(length_bits < 64, "Length must be less than 64");
-
-        let length_flag: u16 = length.map(|_| 1 << 14).unwrap_or(0);
-        let initial: u16 = 1 << 15;
-
-        assert!(frequency < 2048, "Frequency must be less than 2048");
-
-        CHANNEL_1_LENGTH_DUTY_ENVELOPE
-            .set(envelope_settings.as_bits() | duty_cycle.as_bits() | length_bits);
-        CHANNEL_1_FREQUENCY_CONTROL.set(frequency | length_flag | initial);
-    }
-}
-
-#[non_exhaustive]
-pub struct Channel2 {}
-
-impl Channel2 {
-    pub fn play_sound(
-        &self,
-        frequency: u16,
-        length: Option<u8>,
-        envelope_settings: &EnvelopeSettings,
-        duty_cycle: DutyCycle,
-    ) {
-        let length_bits = length.unwrap_or(0) as u16;
-        assert!(length_bits < 64, "Length must be less than 64");
-
-        let length_flag: u16 = length.map(|_| 1 << 14).unwrap_or(0);
-        let initial: u16 = 1 << 15;
-
-        assert!(frequency < 2048, "Frequency must be less than 2048");
-
-        CHANNEL_2_LENGTH_DUTY_ENVELOPE
-            .set(envelope_settings.as_bits() | duty_cycle.as_bits() | length_bits);
-        CHANNEL_2_FREQUENCY_CONTROL.set(frequency | length_flag | initial);
-    }
-}
-
-#[non_exhaustive]
-pub struct Noise {}
-
-impl Noise {
-    pub fn play_sound(
-        &self,
-        length: Option<u8>,
-        envelope_setting: &EnvelopeSettings,
-        frequency_divider: u8,
-        counter_step_width_15: bool,
-        shift_clock_frequency: u8,
-    ) {
-        let length_bits = length.unwrap_or(0) as u16;
-        assert!(length_bits < 64, "length must be less than 16");
-
-        assert!(
-            frequency_divider < 8,
-            "frequency divider must be less than 8"
-        );
-        assert!(
-            shift_clock_frequency < 16,
-            "frequency clock divider must be less than 16"
-        );
-
-        let length_flag: u16 = length.map(|_| 1 << 14).unwrap_or(0);
-        let initial: u16 = 1 << 15;
-
-        let counter_step_bit = if counter_step_width_15 { 0 } else { 1 << 3 };
-
-        CHANNEL_4_LENGTH_ENVELOPE.set(length_bits | envelope_setting.as_bits());
-        CHANNEL_4_FREQUENCY_CONTROL.set(
-            (frequency_divider as u16)
-                | counter_step_bit
-                | ((shift_clock_frequency as u16) << 4)
-                | length_flag
-                | initial,
-        )
-    }
-}
-
-pub enum SoundDirection {
-    Increase,
-    Decrease,
-}
-
-impl SoundDirection {
-    fn as_bits(&self) -> u16 {
-        match &self {
-            SoundDirection::Increase => 1,
-            SoundDirection::Decrease => 0,
-        }
-    }
-}
-
-pub struct SweepSettings {
-    number_of_sweep_shifts: u8,
-    sound_direction: SoundDirection,
-    sweep_time: u8,
-}
-
-impl SweepSettings {
-    pub fn new(
-        number_of_sweep_shifts: u8,
-        sound_direction: SoundDirection,
-        sweep_time: u8,
-    ) -> Self {
-        assert!(
-            number_of_sweep_shifts < 8,
-            "Number of sweep shifts must be less than 8"
-        );
-        assert!(sweep_time < 8, "Sweep time must be less than 8");
-
-        SweepSettings {
-            number_of_sweep_shifts,
-            sound_direction,
-            sweep_time,
-        }
-    }
-
-    fn as_bits(&self) -> u16 {
-        ((self.number_of_sweep_shifts as u16) & 0b111)
-            | ((1 - self.sound_direction.as_bits()) << 3) // sweep works backwards
-            | ((self.sweep_time as u16) & 0b111) << 4
-    }
-}
-
-impl Default for SweepSettings {
-    fn default() -> Self {
-        SweepSettings::new(0, SoundDirection::Increase, 0)
-    }
-}
-
-pub struct EnvelopeSettings {
-    step_time: u8,
-    direction: SoundDirection,
-    initial_volume: u8,
-}
-
-impl EnvelopeSettings {
-    pub fn new(step_time: u8, direction: SoundDirection, initial_volume: u8) -> Self {
-        assert!(step_time < 8, "Step time must be less than 8");
-        assert!(initial_volume < 16, "Initial volume must be less that 16");
-        EnvelopeSettings {
-            step_time,
-            direction,
-            initial_volume,
-        }
-    }
-
-    fn as_bits(&self) -> u16 {
-        (self.step_time as u16) << 8
-            | (self.direction.as_bits() << 11)
-            | ((self.initial_volume as u16) << 12)
-    }
-}
-
-impl Default for EnvelopeSettings {
-    fn default() -> Self {
-        EnvelopeSettings::new(0, SoundDirection::Increase, 15)
-    }
-}
-
-pub enum DutyCycle {
-    OneEighth,
-    OneQuarter,
-    Half,
-    ThreeQuarters,
-}
-
-impl DutyCycle {
-    fn as_bits(&self) -> u16 {
-        use DutyCycle::*;
-
-        match &self {
-            OneEighth => 0,
-            OneQuarter => 1,
-            Half => 2,
-            ThreeQuarters => 3,
-        }
-    }
-}
+pub mod dmg;
+pub mod mixer;