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rp2040 zero rainbow using palette #82

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rp2040 zero rainbow using palette #82

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1 change: 1 addition & 0 deletions boards/waveshare-rp2040-zero/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@ repository = "https://github.com/rp-rs/rp-hal-boards.git"

[dependencies]
cortex-m-rt = { workspace = true, optional = true }
palette = { version = "0.7.6", default-features = false, features = ["libm"] }
rp2040-boot2 = { workspace = true, optional = true }
rp2040-hal.workspace = true

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46 changes: 22 additions & 24 deletions boards/waveshare-rp2040-zero/examples/waveshare_rp2040_zero_neopixel_rainbow.rs
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Expand Up @@ -8,6 +8,9 @@

use core::iter::once;
use embedded_hal::delay::DelayNs;
use palette::rgb::Rgb;
use palette::{FromColor, Hsl};
// use palette::Hsl;
use panic_halt as _;
use smart_leds::{brightness, SmartLedsWrite, RGB8};
use waveshare_rp2040_zero::entry;
Expand Down Expand Up @@ -71,31 +74,26 @@ fn main() -> ! {
);

// Infinite colour wheel loop
let mut n: u8 = 128;
let mut hue: f64 = 0.0;
let mut timer = timer; // rebind to force a copy of the timer
loop {
ws.write(brightness(once(wheel(n)), 32)).unwrap();
n = n.wrapping_add(1);

timer.delay_ms(25);
}
}

/// 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()
ws.write(brightness(
once({
let hsl = Hsl::<Rgb, _>::new(hue as f64, 1.0, 0.5);
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hue is already an f64 from its declaration. No need to cast it here.

let rgb = Rgb::from_color(hsl).into_format();
RGB8::new(rgb.red, rgb.green, rgb.blue)
}),
{
// 0 is off and 1 is max brightness
let brightness = 0.05 as f64;
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Suggested change
let brightness = 0.05 as f64;
let brightness = 0.05f64;

(brightness * u8::MAX as f64) as u8
Comment on lines +87 to +89
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The previous code uses 32 as brightness which is 12.5% not 5%.
Why not leaving the value 32 and only adding a comment like /* 12.5% */

},
))
.unwrap();
hue += 360.0 / 6.0 / u8::MAX as f64;
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All these values are constants. What’s the intent in that math?

The current code turns the wheel by (1/255)rad (~1.41°) per iteration.
We don’t need this to match strictly. This should be enough:

Suggested change
hue += 360.0 / 6.0 / u8::MAX as f64;
hue += 1.0; // advance by 1°

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The intent is that there are 256 steps of changes in a value of either r, g, b in every 1/6 of 360 degrees, so adding the hue by 360/6/256 makes sure that there will actually be a change in pixels every iteration of the loop. This can be changed to 1 if that's what's prefered by this project.

if hue >= 360.0 {
hue -= 360.0;
}
timer.delay_ms(1)
}
}