Add an example using the Feather RP2040's onboard NeoPixel

This uses PIO just like the Pro Micro does.

boards/feather_rp2040/Cargo.toml

@@ -19,7 +19,11 @@ embedded-time = "0.12.0"
 panic-halt= "0.2.0"
 embedded-hal ="0.2.5"
 rp2040-boot2 = { git = "https://github.com/rp-rs/rp2040-boot2-rs",  rev = "d2128ef9875e91e454dd0fb0d747c7439ae0627b" }
+nb = "1.0.0"
+smart-leds = "0.3.0"
+pio = { git = "https://github.com/rp-rs/pio-rs.git", branch = "main" }
+ws2812-pio = { git = "https://github.com/ithinuel/ws2812-pio-rs" }
 
 [features]
 default = ["rt"]
-rt = ["cortex-m-rt","rp2040-hal/rt"]
+rt = ["cortex-m-rt","rp2040-hal/rt"]

boards/feather_rp2040/README.md

@@ -55,12 +55,16 @@ $ cargo install elf2uf2-rs, then repeating the `cargo run` command above.
 
 ### [feather_blinky](./examples/feather_blinky.rs)
 
-Flashes the Feather's on-board LED on and off.
+Flashes the Feather's onboard LED on and off.
+
+### [feather_neopixel_rainbow](./examples/feather_neopixel_rainbow.rs)
+
+Flows smoothly through various colors on the Feather's onboard NeoPixel LED.
 
 ## Contributing
 
 Contributions are what make the open source community such an amazing place to
-be learn, inspire, and create. Any contributions you make are **greatly
+be, learn, inspire, and create. Any contributions you make are **greatly
 appreciated**.
 
 The steps are:

boards/feather_rp2040/examples/feather_neopixel_rainbow.rs

@@ -0,0 +1,100 @@
+//! Rainbow effect color wheel using the onboard NeoPixel on an Adafruit Feather RP2040 board
+//!
+//! This flows smoothly through various colors on the onboard NeoPixel.
+//! Uses the `ws2812_pio` driver to control the NeoPixel, which in turns uses the
+//! RP2040's PIO block.
+#![no_std]
+#![no_main]
+
+use core::iter::once;
+use cortex_m_rt::entry;
+use embedded_hal::timer::CountDown;
+use embedded_time::duration::Extensions;
+use feather_rp2040::{
+    hal::{
+        clocks::{init_clocks_and_plls, Clock},
+        gpio::{FunctionPio0, Pin},
+        pac,
+        sio::Sio,
+        timer::Timer,
+        watchdog::Watchdog,
+    },
+    Pins, XOSC_CRYSTAL_FREQ,
+};
+use panic_halt as _;
+use smart_leds::{brightness, SmartLedsWrite, RGB8};
+use ws2812_pio::Ws2812;
+#[link_section = ".boot2"]
+#[used]
+pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_GD25Q64CS;
+
+#[entry]
+fn main() -> ! {
+    let mut pac = pac::Peripherals::take().unwrap();
+
+    let mut watchdog = Watchdog::new(pac.WATCHDOG);
+
+    let clocks = init_clocks_and_plls(
+        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 = Pins::new(
+        pac.IO_BANK0,
+        pac.PADS_BANK0,
+        sio.gpio_bank0,
+        &mut pac.RESETS,
+    );
+
+    let _neopixel: Pin<_, FunctionPio0> = pins.neopixel.into_mode();
+
+    let timer = Timer::new(pac.TIMER);
+    let mut delay = timer.count_down();
+
+    // Configure the addressable LED
+    let mut ws = Ws2812::new(
+        // The onboard NeoPixel is attached to GPIO pin #16 on the Feather RP2040.
+        16,
+        pac.PIO0,
+        &mut pac.RESETS,
+        clocks.peripheral_clock.freq(),
+        timer.count_down(),
+    );
+
+    // Infinite colour wheel loop
+    let mut n: u8 = 128;
+    loop {
+        ws.write(brightness(once(wheel(n)), 32)).unwrap();
+        n = n.wrapping_add(1);
+
+        delay.start(25.milliseconds());
+        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()
+    }
+}