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//! This example shows how to create a pwm using the PIO module in the RP235x chip.
#![no_std]
#![no_main]
use core::time::Duration;
use embassy_executor::Spawner;
use embassy_rp::bind_interrupts;
use embassy_rp::peripherals::PIO0;
use embassy_rp::pio::{Instance, InterruptHandler, Pio};
use embassy_rp::pio_programs::pwm::{PioPwm, PioPwmProgram};
use embassy_time::Timer;
use {defmt_rtt as _, panic_probe as _};
const DEFAULT_MIN_PULSE_WIDTH: u64 = 1000; // uncalibrated default, the shortest duty cycle sent to a servo
const DEFAULT_MAX_PULSE_WIDTH: u64 = 2000; // uncalibrated default, the longest duty cycle sent to a servo
const DEFAULT_MAX_DEGREE_ROTATION: u64 = 160; // 160 degrees is typical
const REFRESH_INTERVAL: u64 = 20000; // The period of each cycle
bind_interrupts!(struct Irqs {
PIO0_IRQ_0 => InterruptHandler<PIO0>;
});
pub struct ServoBuilder<'d, T: Instance, const SM: usize> {
pwm: PioPwm<'d, T, SM>,
period: Duration,
min_pulse_width: Duration,
max_pulse_width: Duration,
max_degree_rotation: u64,
}
impl<'d, T: Instance, const SM: usize> ServoBuilder<'d, T, SM> {
pub fn new(pwm: PioPwm<'d, T, SM>) -> Self {
Self {
pwm,
period: Duration::from_micros(REFRESH_INTERVAL),
min_pulse_width: Duration::from_micros(DEFAULT_MIN_PULSE_WIDTH),
max_pulse_width: Duration::from_micros(DEFAULT_MAX_PULSE_WIDTH),
max_degree_rotation: DEFAULT_MAX_DEGREE_ROTATION,
}
}
pub fn set_period(mut self, duration: Duration) -> Self {
self.period = duration;
self
}
pub fn set_min_pulse_width(mut self, duration: Duration) -> Self {
self.min_pulse_width = duration;
self
}
pub fn set_max_pulse_width(mut self, duration: Duration) -> Self {
self.max_pulse_width = duration;
self
}
pub fn set_max_degree_rotation(mut self, degree: u64) -> Self {
self.max_degree_rotation = degree;
self
}
pub fn build(mut self) -> Servo<'d, T, SM> {
self.pwm.set_period(self.period);
Servo {
pwm: self.pwm,
min_pulse_width: self.min_pulse_width,
max_pulse_width: self.max_pulse_width,
max_degree_rotation: self.max_degree_rotation,
}
}
}
pub struct Servo<'d, T: Instance, const SM: usize> {
pwm: PioPwm<'d, T, SM>,
min_pulse_width: Duration,
max_pulse_width: Duration,
max_degree_rotation: u64,
}
impl<'d, T: Instance, const SM: usize> Servo<'d, T, SM> {
pub fn start(&mut self) {
self.pwm.start();
}
pub fn stop(&mut self) {
self.pwm.stop();
}
pub fn write_time(&mut self, duration: Duration) {
self.pwm.write(duration);
}
pub fn rotate(&mut self, degree: u64) {
let degree_per_nano_second = (self.max_pulse_width.as_nanos() as u64 - self.min_pulse_width.as_nanos() as u64)
/ self.max_degree_rotation;
let mut duration =
Duration::from_nanos(degree * degree_per_nano_second + self.min_pulse_width.as_nanos() as u64);
if self.max_pulse_width < duration {
duration = self.max_pulse_width;
}
self.pwm.write(duration);
}
}
#[embassy_executor::main]
async fn main(_spawner: Spawner) {
let p = embassy_rp::init(Default::default());
let Pio { mut common, sm0, .. } = Pio::new(p.PIO0, Irqs);
let prg = PioPwmProgram::new(&mut common);
let pwm_pio = PioPwm::new(&mut common, sm0, p.PIN_1, &prg);
let mut servo = ServoBuilder::new(pwm_pio)
.set_max_degree_rotation(120) // Example of adjusting values for MG996R servo
.set_min_pulse_width(Duration::from_micros(350)) // This value was detemined by a rough experiment.
.set_max_pulse_width(Duration::from_micros(2600)) // Along with this value.
.build();
servo.start();
let mut degree = 0;
loop {
degree = (degree + 1) % 120;
servo.rotate(degree);
Timer::after_millis(50).await;
}
}
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