RP235x: add example for encoder with status register

examples/rp23/src/bin/pio_rotary_encoder_rxf.rs

@@ -0,0 +1,116 @@
+//! This example shows how to use the PIO module in the RP235x to read a quadrature rotary encoder.
+//! It differs from the other example in that it uses the RX FIFO as a status register
+
+#![no_std]
+#![no_main]
+
+use defmt::info;
+use embassy_executor::Spawner;
+use embassy_rp::block::ImageDef;
+use embassy_rp::gpio::Pull;
+use embassy_rp::peripherals::PIO0;
+use embassy_rp::{bind_interrupts, pio};
+use embassy_time::Timer;
+use fixed::traits::ToFixed;
+use pio::{Common, Config, FifoJoin, Instance, InterruptHandler, Pio, PioPin, ShiftDirection, StateMachine};
+use {defmt_rtt as _, panic_probe as _};
+
+#[link_section = ".start_block"]
+#[used]
+pub static IMAGE_DEF: ImageDef = ImageDef::secure_exe();
+
+// Program metadata for `picotool info`
+#[link_section = ".bi_entries"]
+#[used]
+pub static PICOTOOL_ENTRIES: [embassy_rp::binary_info::EntryAddr; 4] = [
+    embassy_rp::binary_info::rp_program_name!(c"example_pio_rotary_encoder_rxf"),
+    embassy_rp::binary_info::rp_cargo_version!(),
+    embassy_rp::binary_info::rp_program_description!(c"Rotary encoder (RXF)"),
+    embassy_rp::binary_info::rp_program_build_attribute!(),
+];
+
+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!(
+            "start:"
+            // encoder count is stored in X
+            "mov isr, x"
+            // and then moved to the RX FIFO register
+            "mov rxfifo[0], isr"
+
+            // wait for encoder transition
+            "wait 1 pin 1"
+            "wait 0 pin 1"
+
+            "set y, 0"
+            "mov y, pins[1]"
+
+            // update X depending on pin 1
+            "jmp !y decr"
+
+            // this is just a clever way of doing x++
+            "mov x, ~x"
+            "jmp x--, incr"
+            "incr:"
+            "mov x, ~x"
+            "jmp start"
+
+            // and this is x--
+            "decr:"
+            "jmp x--, start"
+        );
+
+        let mut cfg = Config::default();
+        cfg.set_in_pins(&[&pin_a, &pin_b]);
+        cfg.fifo_join = FifoJoin::RxAsStatus;
+        cfg.shift_in.direction = ShiftDirection::Left;
+        cfg.clock_divider = 10_000.to_fixed();
+        cfg.use_program(&pio.load_program(&prg.program), &[]);
+        sm.set_config(&cfg);
+
+        sm.set_enable(true);
+        Self { sm }
+    }
+
+    pub async fn read(&mut self) -> u32 {
+        self.sm.get_rxf_entry(0)
+    }
+}
+
+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);
+
+    loop {
+        info!("Count: {}", encoder.read().await);
+        Timer::after_millis(1000).await;
+    }
+}