rgb_leds.rs

//! # Rainbow Example for Cytron Maker Pi rp2040
//!
//! Runs a rainbow-effect colour wheel on the on-board LEDs.
//!
//! Uses the `ws2812_pio` driver to control the LEDs, which in turns uses the
//! RP2040's PIO block.

#![no_std]
#![no_main]

use cortex_m_rt::entry;
use embedded_hal::timer::CountDown;
use fugit::ExtU32;
use panic_halt as _;

// Make an alias for our board support package so copying examples to other boards is easier
use cytron_maker_pi_rp2040 as bsp;

use bsp::hal::{
    clocks::{init_clocks_and_plls, Clock},
    gpio::{FunctionPio0, Pin},
    pac,
    sio::Sio,
    timer::Timer,
    watchdog::Watchdog,
};
use rp2040_hal::pio::PIOExt;
use smart_leds::{brightness, SmartLedsWrite, RGB8};
use ws2812_pio::Ws2812;

/// Entry point to our bare-metal application.
///
/// The `#[entry]` macro ensures the Cortex-M start-up code calls this
/// function as soon as all global variables are initialised.
///
/// The function configures the RP2040 peripherals, then the LED, then runs
/// the colour wheel in an infinite loop.
#[entry]
fn main() -> ! {
    // Configure the RP2040 peripherals

    let mut pac = pac::Peripherals::take().unwrap();
    let mut watchdog = Watchdog::new(pac.WATCHDOG);

    let clocks = init_clocks_and_plls(
        bsp::XOSC_CRYSTAL_FREQ,
        pac.XOSC,
        pac.CLOCKS,
        pac.PLL_SYS,
        pac.PLL_USB,
        &mut pac.RESETS,
        &mut watchdog,
    )
    .ok()
    .unwrap();

    let sio = Sio::new(pac.SIO);

    let pins = bsp::Pins::new(
        pac.IO_BANK0,
        pac.PADS_BANK0,
        sio.gpio_bank0,
        &mut pac.RESETS,
    );

    let smartleds_pin: Pin<_, FunctionPio0, _> = pins.smartleds.into_function();

    let timer = Timer::new(pac.TIMER, &mut pac.RESETS, &clocks);
    let mut delay = timer.count_down();

    // Configure the addressable LED
    let (mut pio, sm0, _, _, _) = pac.PIO0.split(&mut pac.RESETS);
    let mut ws = Ws2812::new(
        smartleds_pin,
        &mut pio,
        sm0,
        clocks.peripheral_clock.freq(),
        timer.count_down(),
    );

    // Infinite colour wheel loop
    let mut n: u8 = 128;
    loop {
        // Put the second LED approximately 1/3 ahead on the color wheel
        let second_led_n = n.wrapping_add(85);
        let leds = [wheel(n), wheel(second_led_n)];
        ws.write(brightness(leds.iter().cloned(), 32)).unwrap();
        n = n.wrapping_add(1);

        delay.start(25.millis());
        let _ = nb::block!(delay.wait());
    }
}

/// Convert a number from `0..=255` to an RGB color triplet.
///
/// The colours are a transition from red, to green, to blue and back to red.
fn wheel(mut wheel_pos: u8) -> RGB8 {
    wheel_pos = 255 - wheel_pos;
    if wheel_pos < 85 {
        // No green in this sector - red and blue only
        (255 - (wheel_pos * 3), 0, wheel_pos * 3).into()
    } else if wheel_pos < 170 {
        // No red in this sector - green and blue only
        wheel_pos -= 85;
        (0, wheel_pos * 3, 255 - (wheel_pos * 3)).into()
    } else {
        // No blue in this sector - red and green only
        wheel_pos -= 170;
        (wheel_pos * 3, 255 - (wheel_pos * 3), 0).into()
    }
}