rp: Add PIO rotary encoder example

examples/rp/src/bin/pio_rotary_encoder.rs

@@ -0,0 +1,91 @@
+//! This example shows how to use the PIO module in the RP2040 to read a quadrature rotary encoder.
+
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::info;
+use embassy_executor::Spawner;
+use embassy_rp::gpio::Pull;
+use embassy_rp::peripherals::PIO0;
+use embassy_rp::{bind_interrupts, pio};
+use fixed::traits::ToFixed;
+use pio::{Common, Config, FifoJoin, Instance, InterruptHandler, Pio, PioPin, ShiftDirection, StateMachine};
+use {defmt_rtt as _, panic_probe as _};
+
+bind_interrupts!(struct Irqs {
+    PIO0_IRQ_0 => InterruptHandler<PIO0>;
+});
+
+pub struct PioEncoder<'d, T: Instance, const SM: usize> {
+    sm: StateMachine<'d, T, SM>,
+}
+
+impl<'d, T: Instance, const SM: usize> PioEncoder<'d, T, SM> {
+    pub fn new(
+        pio: &mut Common<'d, T>,
+        mut sm: StateMachine<'d, T, SM>,
+        pin_a: impl PioPin,
+        pin_b: impl PioPin,
+    ) -> Self {
+        let mut pin_a = pio.make_pio_pin(pin_a);
+        let mut pin_b = pio.make_pio_pin(pin_b);
+        pin_a.set_pull(Pull::Up);
+        pin_b.set_pull(Pull::Up);
+        sm.set_pin_dirs(pio::Direction::In, &[&pin_a, &pin_b]);
+
+        let prg = pio_proc::pio_asm!(
+            r#"
+            wait 1 pin 1       
+            .wrap_target
+                wait 0 pin 1
+                in pins, 2
+                push               
+                wait 1 pin 1       
+                .wrap
+        "#
+        );
+
+        let mut cfg = Config::default();
+        cfg.set_in_pins(&[&pin_a, &pin_b]);
+        cfg.fifo_join = FifoJoin::RxOnly;
+        cfg.use_program(&pio.load_program(&prg.program), &[]);
+        cfg.shift_in.direction = ShiftDirection::Left;
+        cfg.clock_divider = 10_000.to_fixed();
+        sm.set_config(&cfg);
+        sm.set_enable(true);
+        Self { sm }
+    }
+
+    pub async fn read(&mut self) -> Direction {
+        loop {
+            match self.sm.rx().wait_pull().await {
+                0 => return Direction::CounterClockwise,
+                1 => return Direction::Clockwise,
+                _ => {}
+            }
+        }
+    }
+}
+
+pub enum Direction {
+    Clockwise,
+    CounterClockwise,
+}
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_rp::init(Default::default());
+    let Pio { mut common, sm0, .. } = Pio::new(p.PIO0, Irqs);
+
+    let mut encoder = PioEncoder::new(&mut common, sm0, p.PIN_4, p.PIN_5);
+
+    let mut count = 0;
+    loop {
+        info!("Count: {}", count);
+        count += match encoder.read().await {
+            Direction::Clockwise => 1,
+            Direction::CounterClockwise => -1,
+        };
+    }
+}