examples: mega2560: Add RGB-LED example

examples/arduino-mega2560/src/bin/mega2560-rgb-led.rs

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+//! This example demonstrates how to fade an RGB LED connected to an Arduino board.
+//!
+//! Wiring:
+//! - Connect the common cathode of the RGB LED to GND.
+//! - Connect the red LED anode to pin D6 through a current-limiting resistor.
+//! - Connect the green LED anode to pin D5 through a current-limiting resistor.
+//! - Connect the blue LED anode to pin D3 through a current-limiting resistor.
+//!
+//! Note: The current-limiting resistor values depend on the specific RGB LED and the desired brightness.
+//! Typically, a resistor value between 220Ω and 1kΩ is suitable.
+
+#![no_std]
+#![no_main]
+
+use panic_halt as _;
+use arduino_hal::simple_pwm::IntoPwmPin;
+use arduino_hal::simple_pwm::Prescaler;
+use arduino_hal::simple_pwm::{Timer3Pwm, Timer4Pwm};
+
+#[arduino_hal::entry]
+fn main() -> ! {
+    let dp = arduino_hal::Peripherals::take().unwrap();
+    let pins = arduino_hal::pins!(dp);
+
+    let timer0 = Timer4Pwm::new(dp.TC4, Prescaler::Prescale64);
+    let timer1 = Timer3Pwm::new(dp.TC3, Prescaler::Prescale64);
+
+    let mut d6 = pins.d6.into_output().into_pwm(&timer0);
+    let mut d5 = pins.d5.into_output().into_pwm(&timer1);
+    let mut d3 = pins.d3.into_output().into_pwm(&timer1);
+
+    let max_duty_d6 = d6.get_max_duty();
+    let max_duty_d5 = d5.get_max_duty();
+    let max_duty_d3 = d3.get_max_duty();
+
+    let delay_time = 10;
+
+    d6.enable();
+    d5.enable();
+    d3.enable();
+
+    loop {
+        // Fade in/out red
+        for i in (0..=max_duty_d6).chain((0..=max_duty_d6 - 1).rev()) {
+            d6.set_duty(i);
+            arduino_hal::delay_ms(delay_time);
+        }
+
+        // Fade in/out green
+        for i in (0..=max_duty_d5).chain((0..=max_duty_d5 - 1).rev()) {
+            d5.set_duty(i);
+            arduino_hal::delay_ms(delay_time);
+        }
+
+        // Fade in/out blue
+        for i in (0..=max_duty_d3).chain((0..=max_duty_d3 - 1).rev()) {
+            d3.set_duty(i);
+            arduino_hal::delay_ms(delay_time);
+        }
+    }
+}