feat: create timer struct and stub 0xff07

src/timer.rs

@@ -0,0 +1,68 @@
+#[derive(Debug, Clone, Copy)]
+pub struct Timer {
+    pub control: TimerControl,
+}
+
+impl Default for Timer {
+    fn default() -> Self {
+        Self {
+            control: 0x00.into(),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+enum TimerSpeed {
+    Freq4096Hz,
+    Freq262144Hz,
+    Freq65536Hz,
+    Freq16384Hz,
+}
+
+impl From<u8> for TimerSpeed {
+    fn from(byte: u8) -> Self {
+        match byte {
+            0x00 => Self::Freq4096Hz,
+            0x01 => Self::Freq262144Hz,
+            0x10 => Self::Freq65536Hz,
+            0x11 => Self::Freq16384Hz,
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl From<TimerSpeed> for u8 {
+    fn from(speed: TimerSpeed) -> Self {
+        match speed {
+            TimerSpeed::Freq4096Hz => 0x00,
+            TimerSpeed::Freq262144Hz => 0x01,
+            TimerSpeed::Freq65536Hz => 0x10,
+            TimerSpeed::Freq16384Hz => 0x11,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+pub struct TimerControl {
+    enabled: bool,
+    speed: TimerSpeed,
+}
+
+impl From<u8> for TimerControl {
+    fn from(byte: u8) -> Self {
+        let byte = byte & 0x07; // Clear everything but last 3 bits
+
+        Self {
+            enabled: (byte >> 2) == 0x01,
+            speed: (byte & 0x03).into(), // Clear everything but last 2 bits
+        }
+    }
+}
+
+impl From<TimerControl> for u8 {
+    fn from(control: TimerControl) -> Self {
+        let byte: u8 = control.speed.into(); // Get bit 1 and 0.
+
+        (byte & !(1u8 << 2)) | ((control.enabled as u8) << 2) // specifically manibulate bit 2
+    }
+}