fw-rust: Handle screens differently, use encoder

Handle the screens differently and implement rotary encoder support.

firmware/rust/src/rotary.rs

@@ -0,0 +1,51 @@
+use embedded_hal::digital::v2::InputPin;
+
+pub struct Rotary<A, B> {
+    pin_a: A,
+    pin_b: B,
+    state: u8,
+}
+
+pub enum Direction {
+    Clockwise,
+    CounterClockwise,
+    None,
+}
+
+impl<A, B> Rotary<A, B>
+where
+    A: InputPin,
+    B: InputPin,
+{
+    pub fn new(pin_a: A, pin_b: B) -> Self {
+        Self {
+            pin_a,
+            pin_b,
+            state: 0,
+        }
+    }
+
+    pub fn update(&mut self) -> Direction {
+        let a = self.pin_a.is_low();
+        let b = self.pin_b.is_low();
+
+        let new_state = match (a, b) {
+            (Ok(true), Ok(true)) => 0b00,
+            (Ok(true), Ok(false)) => 0b01,
+            (Ok(false), Ok(true)) => 0b10,
+            (Ok(false), Ok(false)) => 0b11,
+            _ => return Direction::None,
+        };
+
+        let direction = match (self.state, new_state) {
+            (0b10, 0b11) => Direction::Clockwise,
+            (0b01, 0b00) => Direction::Clockwise,
+            (0b01, 0b11) => Direction::CounterClockwise,
+            (0b10, 0b00) => Direction::CounterClockwise,
+            _ => Direction::None,
+        };
+
+        self.state = new_state;
+        direction
+    }
+}