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//! This example shows how to use PWM (Pulse Width Modulation) in the RP2040 chip.
//!
//! We demonstrate two ways of using PWM:
//! 1. Via config
//! 2. Via setting a duty cycle
#![no_std]
#![no_main]
use defmt::*;
use embassy_executor::Spawner;
use embassy_rp::peripherals::{PIN_25, PIN_4, PWM_SLICE2, PWM_SLICE4};
use embassy_rp::pwm::{Config, Pwm, SetDutyCycle};
use embassy_rp::Peri;
use embassy_time::Timer;
use {defmt_rtt as _, panic_probe as _};
#[embassy_executor::main]
async fn main(spawner: Spawner) {
let p = embassy_rp::init(Default::default());
spawner.spawn(pwm_set_config(p.PWM_SLICE4, p.PIN_25).unwrap());
spawner.spawn(pwm_set_dutycycle(p.PWM_SLICE2, p.PIN_4).unwrap());
}
/// Demonstrate PWM by modifying & applying the config
///
/// Using the onboard led, if You are using a different Board than plain Pico2 (i.e. W variant)
/// you must use another slice & pin and an appropriate resistor.
#[embassy_executor::task]
async fn pwm_set_config(slice4: Peri<'static, PWM_SLICE4>, pin25: Peri<'static, PIN_25>) {
let mut c = Config::default();
c.top = 32_768;
c.compare_b = 8;
let mut pwm = Pwm::new_output_b(slice4, pin25, c.clone());
loop {
info!("current LED duty cycle: {}/32768", c.compare_b);
Timer::after_secs(1).await;
c.compare_b = c.compare_b.rotate_left(4);
pwm.set_config(&c);
}
}
/// Demonstrate PWM by setting duty cycle
///
/// Using GP4 in Slice2, make sure to use an appropriate resistor.
#[embassy_executor::task]
async fn pwm_set_dutycycle(slice2: Peri<'static, PWM_SLICE2>, pin4: Peri<'static, PIN_4>) {
// If we aim for a specific frequency, here is how we can calculate the top value.
// The top value sets the period of the PWM cycle, so a counter goes from 0 to top and then wraps around to 0.
// Every such wraparound is one PWM cycle. So here is how we get 25KHz:
let desired_freq_hz = 25_000;
let clock_freq_hz = embassy_rp::clocks::clk_sys_freq();
let divider = 16u8;
let period = (clock_freq_hz / (desired_freq_hz * divider as u32)) as u16 - 1;
let mut c = Config::default();
c.top = period;
c.divider = divider.into();
let mut pwm = Pwm::new_output_a(slice2, pin4, c.clone());
loop {
// 100% duty cycle, fully on
pwm.set_duty_cycle_fully_on().unwrap();
Timer::after_secs(1).await;
// 66% duty cycle. Expressed as simple percentage.
pwm.set_duty_cycle_percent(66).unwrap();
Timer::after_secs(1).await;
// 25% duty cycle. Expressed as 32768/4 = 8192.
pwm.set_duty_cycle(c.top / 4).unwrap();
Timer::after_secs(1).await;
// 0% duty cycle, fully off.
pwm.set_duty_cycle_fully_off().unwrap();
Timer::after_secs(1).await;
}
}
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