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//! 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::gpio::Pull;
use embassy_rp::peripherals::PIO0;
use embassy_rp::pio::program::pio_asm;
use embassy_rp::{Peri, 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 _};
// Program metadata for `picotool info`
#[unsafe(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: Peri<'d, impl PioPin>,
pin_b: Peri<'d, 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_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) -> i32 {
self.sm.get_rxf_entry(0) as i32
}
}
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;
}
}
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