Move rotary encoder handling to a separate module

Cargo.toml

@@ -30,6 +30,10 @@ features = ["stm32f103", "rt"]
 version = "0.5.3"
 features = ["rt", "stm32f103", "medium"]
 
+[dependencies.either]
+default-features = false
+version = "1.5.3"
+
 [[bin]]
 name = "blue_pill_more"
 test = false

src/main.rs

@@ -35,8 +35,6 @@ use stm32f1xx_hal::{
     prelude::*,
 };
 
-use embedded_hal::digital::v2::InputPin;
-
 use switch_hal::{IntoSwitch, InputSwitch, OutputSwitch, ToggleableOutputSwitch};
 
 use ssd1306::{
@@ -54,6 +52,9 @@ use embedded_graphics::{
 
 use arrayvec::ArrayString;
 
+mod rotary;
+use rotary::{Direction, Rotary};
+
 type CLKPIN = PA8<Input<Floating>>;
 type DTPIN = PA9<Input<Floating>>;
 
@@ -104,6 +105,8 @@ fn main() -> ! {
     let sw = gpioa.pa10
         .into_floating_input(&mut gpioa.crh)
         .into_active_low_switch();
+
+    // Set up the rotary encoder pins for use with the interrupt
     init_encoder_pins(clk, dt, &mut afio, &dev_periph.EXTI);
 
     // Configure pin C13 to drive the "PC13" LED as an active-low switch
@@ -111,7 +114,7 @@ fn main() -> ! {
         .into_push_pull_output(&mut gpioc.crh)
         .into_active_low_switch();
 
-    // Configure the I2C pins we are using to the correct mode
+    // Configure the I2C pins we are using for the display to the correct mode
     let scl = gpiob.pb10.into_alternate_open_drain(&mut gpiob.crh);
     let sda = gpiob.pb11.into_alternate_open_drain(&mut gpiob.crh);
 
@@ -131,9 +134,6 @@ fn main() -> ! {
         1000,
     );
 
-    // Turn the LED on via the OutputPin trait
-    led.on().unwrap();
-
     // Initialize the display
     let mut display: GraphicsMode<_> = Builder::new()
         .with_i2c_addr(0x3c)
@@ -144,6 +144,13 @@ fn main() -> ! {
     // Every set of commands to the display is buffered until we flush it
     display.flush().unwrap();
 
+    // Enable interrupts
+    unsafe {
+        core_periph.NVIC.set_priority(Interrupt::EXTI9_5, 1);
+        NVIC::unmask(Interrupt::EXTI9_5);
+    }
+    NVIC::unpend(Interrupt::EXTI9_5);
+
     // We will draw a fixed message on the screen and also a moving circle
 
     const C_RADIUS: i32 = 8;
@@ -156,17 +163,12 @@ fn main() -> ! {
     let t = Text::new("Hello Rust!", Point::new(20, 16))
         .into_styled(TextStyle::new(Font6x8, BinaryColor::On));
 
+    // Turn the LED on via the OutputPin trait
+    led.on().unwrap();
 
     // Very brief delay before the loop, just to show how
     delay.delay_us(10_u8);
 
-    // Enable interrupts
-    unsafe {
-        core_periph.NVIC.set_priority(Interrupt::EXTI9_5, 1);
-        NVIC::unmask(Interrupt::EXTI9_5);
-    }
-    NVIC::unpend(Interrupt::EXTI9_5);
-
     let mut button_last = false;
     // Microcontroller programs never exit main, so we must loop!
     loop {
@@ -194,7 +196,7 @@ fn main() -> ! {
         display.flush().unwrap();
 
         // Control the horizontal position with the knob
-        cx = counter.max(C_RADIUS/2).min(DISPLAY_W-C_RADIUS/2);
+        cx = counter.max(C_RADIUS/2).min(DISPLAY_W - C_RADIUS/2);
         // Wrap the ball back to the top when it falls off the bottom
         cy += 1;
         if cy > (DISPLAY_H + C_RADIUS) { cy = -C_RADIUS };
@@ -220,46 +222,30 @@ fn init_encoder_pins(
 
 #[interrupt]
 fn EXTI9_5() {
-    static mut CLK: Option<CLKPIN> = None;
+    static mut ENC: Option<Rotary<CLKPIN, DTPIN>> = None;
-    static mut DT: Option<DTPIN> = None;
-    static mut PREV_A: bool = false;
-    static mut PREV_C: bool = false;
 
-    let clk_pin = CLK.get_or_insert_with(|| {
+    let enc = ENC.get_or_insert_with(|| {
         cortex_m::interrupt::free(|cs| {
-            CLK_PIN.borrow(cs).replace(None).unwrap()
+            let clk = CLK_PIN.borrow(cs).replace(None).unwrap();
-        })
+            let dt = DT_PIN.borrow(cs).replace(None).unwrap();
-    });
+            Rotary::new(clk, dt)
-    let dt_pin = DT.get_or_insert_with(|| {
-        cortex_m::interrupt::free(|cs| {
-            DT_PIN.borrow(cs).replace(None).unwrap()
         })
     });
 
-    if clk_pin.check_interrupt() {
+    if enc.pin_a.check_interrupt() {
-        let a = clk_pin.is_high().unwrap();
+        match enc.update().unwrap() {
-        let b = dt_pin.is_high().unwrap();
+            Direction::Clockwise => cortex_m::interrupt::free(|cs| {
-        // When A is changing, B should be stable
-        if a != *PREV_A {
-            *PREV_A = a;
-            // Capture B as C whenever it changes from C's last value
-            if b != *PREV_C {
-                *PREV_C = b;
-                if a == b { // Up
-                    cortex_m::interrupt::free(|cs| {
                 COUNT
                     .borrow(cs)
-                            .replace_with(|count| count.wrapping_add(1))
+                    .replace_with(|count| count.wrapping_add(1));
-                    });
+            }),
-                } else {    // Down
+            Direction::CounterClockwise => cortex_m::interrupt::free(|cs| {
-                    cortex_m::interrupt::free(|cs| {
                 COUNT
                     .borrow(cs)
-                            .replace_with(|count| count.wrapping_add(-1))
+                    .replace_with(|count| count.wrapping_add(-1));
-                    });
+            }),
-                }
+            Direction::None => {}
-            }
+        };
-        }
+        enc.pin_a.clear_interrupt_pending_bit();
-        clk_pin.clear_interrupt_pending_bit();
     }
 }

src/rotary.rs

@@ -0,0 +1,59 @@
+use embedded_hal as hal;
+use either::Either;
+use hal::digital::v2::InputPin;
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct Rotary<A, B> {
+    pub pin_a: A,
+    pub pin_b: B,
+    prev_a: bool,
+    prev_c: bool,
+}
+
+/// The encoder direction is either `Clockwise`, `CounterClockwise`, or `None`
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum Direction {
+    /// A clockwise turn
+    Clockwise,
+    /// A counterclockwise turn
+    CounterClockwise,
+    /// No change
+    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,
+            prev_a: false,
+            prev_c: false,
+        }
+    }
+
+    pub fn update(&mut self) -> Result<Direction, Either<A::Error, B::Error>> {
+        let a = self.pin_a.is_high().map_err(Either::Left)?;
+        let dir = if a != self.prev_a {
+            self.prev_a = a;
+            let b = self.pin_b.is_high().map_err(Either::Right)?;
+            if b != self.prev_c {
+                self.prev_c = b;
+                if a == b {
+                    Direction::CounterClockwise
+                } else {
+                    Direction::Clockwise
+                }
+            } else {
+                Direction::None
+            }
+        } else {
+            Direction::None
+        };
+        Ok(dir)
+    }
+}
+