rp: Add PIO stepper motor driver example

1 files changed, 169 insertions, 0 deletions

diff --git a/examples/rp/src/bin/pio_stepper.rs b/examples/rp/src/bin/pio_stepper.rs
new file mode 100644
index 000000000..02fb20699
--- /dev/null
+++ b/examples/rp/src/bin/pio_stepper.rs
@@ -0,0 +1,169 @@
+//! This example shows how to use the PIO module in the RP2040 to implement a stepper motor driver
+//! for a 5-wire stepper such as the 28BYJ-48. You can halt an ongoing rotation by dropping the future.
+
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+use core::mem::{self, MaybeUninit};
+
+use defmt::info;
+use embassy_executor::Spawner;
+use embassy_rp::bind_interrupts;
+use embassy_rp::peripherals::PIO0;
+use embassy_rp::pio::{Common, Config, Direction, Instance, InterruptHandler, Irq, Pio, PioPin, StateMachine};
+use embassy_time::{with_timeout, Duration, Timer};
+use fixed::traits::ToFixed;
+use fixed::types::extra::U8;
+use fixed::FixedU32;
+use {defmt_rtt as _, panic_probe as _};
+
+bind_interrupts!(struct Irqs {
+    PIO0_IRQ_0 => InterruptHandler<PIO0>;
+});
+
+pub struct PioStepper<'d, T: Instance, const SM: usize> {
+    irq: Irq<'d, T, SM>,
+    sm: StateMachine<'d, T, SM>,
+}
+
+impl<'d, T: Instance, const SM: usize> PioStepper<'d, T, SM> {
+    pub fn new(
+        pio: &mut Common<'d, T>,
+        mut sm: StateMachine<'d, T, SM>,
+        irq: Irq<'d, T, SM>,
+        pin0: impl PioPin,
+        pin1: impl PioPin,
+        pin2: impl PioPin,
+        pin3: impl PioPin,
+    ) -> Self {
+        let prg = pio_proc::pio_asm!(
+            "pull block",
+            "mov x, osr",
+            "pull block",
+            "mov y, osr",
+            "jmp !x end",
+            "loop:",
+            "jmp !osre step",
+            "mov osr, y",
+            "step:",
+            "out pins, 4 [31]"
+            "jmp x-- loop",
+            "end:",
+            "irq 0 rel"
+        );
+        let pin0 = pio.make_pio_pin(pin0);
+        let pin1 = pio.make_pio_pin(pin1);
+        let pin2 = pio.make_pio_pin(pin2);
+        let pin3 = pio.make_pio_pin(pin3);
+        sm.set_pin_dirs(Direction::Out, &[&pin0, &pin1, &pin2, &pin3]);
+        let mut cfg = Config::default();
+        cfg.set_out_pins(&[&pin0, &pin1, &pin2, &pin3]);
+        cfg.clock_divider = (125_000_000 / (100 * 136)).to_fixed();
+        cfg.use_program(&pio.load_program(&prg.program), &[]);
+        sm.set_config(&cfg);
+        sm.set_enable(true);
+        Self { irq, sm }
+    }
+
+    // Set pulse frequency
+    pub fn set_frequency(&mut self, freq: u32) {
+        let clock_divider: FixedU32<U8> = (125_000_000 / (freq * 136)).to_fixed();
+        assert!(clock_divider <= 65536, "clkdiv must be <= 65536");
+        assert!(clock_divider >= 1, "clkdiv must be >= 1");
+        T::PIO.sm(SM).clkdiv().write(|w| w.0 = clock_divider.to_bits() << 8);
+        self.sm.clkdiv_restart();
+    }
+
+    // Full step, one phase
+    pub async fn step(&mut self, steps: i32) {
+        if steps > 0 {
+            self.run(steps, 0b1000_0100_0010_0001_1000_0100_0010_0001).await
+        } else {
+            self.run(-steps, 0b0001_0010_0100_1000_0001_0010_0100_1000).await
+        }
+    }
+
+    // Full step, two phase
+    pub async fn step2(&mut self, steps: i32) {
+        if steps > 0 {
+            self.run(steps, 0b1001_1100_0110_0011_1001_1100_0110_0011).await
+        } else {
+            self.run(-steps, 0b0011_0110_1100_1001_0011_0110_1100_1001).await
+        }
+    }
+
+    // Half step
+    pub async fn step_half(&mut self, steps: i32) {
+        if steps > 0 {
+            self.run(steps, 0b1001_1000_1100_0100_0110_0010_0011_0001).await
+        } else {
+            self.run(-steps, 0b0001_0011_0010_0110_0100_1100_1000_1001).await
+        }
+    }
+
+    async fn run(&mut self, steps: i32, pattern: u32) {
+        self.sm.tx().wait_push(steps as u32).await;
+        self.sm.tx().wait_push(pattern).await;
+        let drop = OnDrop::new(|| {
+            self.sm.clear_fifos();
+            unsafe {
+                self.sm.exec_instr(
+                    pio::InstructionOperands::JMP {
+                        address: 0,
+                        condition: pio::JmpCondition::Always,
+                    }
+                    .encode(),
+                );
+            }
+        });
+        self.irq.wait().await;
+        drop.defuse();
+    }
+}
+
+struct OnDrop<F: FnOnce()> {
+    f: MaybeUninit<F>,
+}
+
+impl<F: FnOnce()> OnDrop<F> {
+    pub fn new(f: F) -> Self {
+        Self { f: MaybeUninit::new(f) }
+    }
+
+    pub fn defuse(self) {
+        mem::forget(self)
+    }
+}
+
+impl<F: FnOnce()> Drop for OnDrop<F> {
+    fn drop(&mut self) {
+        unsafe { self.f.as_ptr().read()() }
+    }
+}
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_rp::init(Default::default());
+    let Pio {
+        mut common, irq0, sm0, ..
+    } = Pio::new(p.PIO0, Irqs);
+
+    let mut stepper = PioStepper::new(&mut common, sm0, irq0, p.PIN_4, p.PIN_5, p.PIN_6, p.PIN_7);
+    stepper.set_frequency(120);
+    loop {
+        info!("CW full steps");
+        stepper.step(1000).await;
+
+        info!("CCW full steps, drop after 1 sec");
+        if let Err(_) = with_timeout(Duration::from_secs(1), stepper.step(i32::MIN)).await {
+            info!("Time's up!");
+            Timer::after(Duration::from_secs(1)).await;
+        }
+
+        info!("CW half steps");
+        stepper.step_half(1000).await;
+
+        info!("CCW half steps");
+        stepper.step_half(-1000).await;
+    }
+}