rp-hal-boards/boards/pico/examples/pico_pwm_blink.rs
Jonathan Pallant (42 Technology) 35f001f61d Polishing the PWM and USB examples.
2021-09-21 10:47:43 +01:00

126 lines
3.3 KiB
Rust

//! # Pico PWM Blink Example
//!
//! Fades the LED on a Pico board using the PWM peripheral.
//!
//! This will fade in/out the LED attached to GP25, which is the pin the Pico
//! uses for the on-board LED.
//!
//! See the `Cargo.toml` file for Copyright and licence details.
#![no_std]
#![no_main]
// The macro for our start-up function
use cortex_m_rt::entry;
// GPIO traits
use embedded_hal::PwmPin;
// Time handling traits
use embedded_time::rate::*;
// Ensure we halt the program on panic (if we don't mention this crate it won't
// be linked)
use panic_halt as _;
// Pull in any important traits
use pico::hal::prelude::*;
// A shorter alias for the Peripheral Access Crate, which provides low-level
// register access
use pico::hal::pac;
// A shorter alias for the Hardware Abstraction Layer, which provides
// higher-level drivers.
use pico::hal;
/// The linker will place this boot block at the start of our program image. We
/// need this to help the ROM bootloader get our code up and running.
#[link_section = ".boot2"]
#[used]
pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER;
// The minimum PWM value (i.e. LED brightness) we want
const LOW: u16 = 0;
// The maximum PWM value (i.e. LED brightness) we want
const HIGH: u16 = 25000;
/// Entry point to our bare-metal application.
///
/// The `#[entry]` macro ensures the Cortex-M start-up code calls this function
/// as soon as all global variables are initialised.
///
/// The function configures the RP2040 peripherals, then fades the LED in an
/// infinite loop.
#[entry]
fn main() -> ! {
// Grab our singleton objects
let mut pac = pac::Peripherals::take().unwrap();
let core = pac::CorePeripherals::take().unwrap();
// Set up the watchdog driver - needed by the clock setup code
let mut watchdog = hal::watchdog::Watchdog::new(pac.WATCHDOG);
// Configure the clocks
//
// Our default is 12 MHz crystal input, 125 MHz system clock
let clocks = hal::clocks::init_clocks_and_plls(
pico::XOSC_CRYSTAL_FREQ,
pac.XOSC,
pac.CLOCKS,
pac.PLL_SYS,
pac.PLL_USB,
&mut pac.RESETS,
&mut watchdog,
)
.ok()
.unwrap();
// The single-cycle I/O block controls our GPIO pins
let sio = hal::sio::Sio::new(pac.SIO);
// Set the pins up according to their function on this particular board
let pins = pico::Pins::new(
pac.IO_BANK0,
pac.PADS_BANK0,
sio.gpio_bank0,
&mut pac.RESETS,
);
// The delay object lets us wait for specified amounts of time (in
// milliseconds)
let mut delay = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().integer());
// Init PWMs
let mut pwm_slices = hal::pwm::Slices::new(pac.PWM, &mut pac.RESETS);
// Configure PWM4
let pwm = &mut pwm_slices.pwm4;
pwm.set_ph_correct();
pwm.enable();
// Output channel B on PWM4 to the LED pin
let channel = &mut pwm.channel_b;
channel.output_to(pins.led);
// Infinite loop, fading LED up and down
loop {
// Ramp brightness up
for i in (LOW..=HIGH).skip(100) {
delay.delay_us(8);
channel.set_duty(i);
}
// Ramp brightness down
for i in (LOW..=HIGH).rev().skip(100) {
delay.delay_us(8);
channel.set_duty(i);
}
delay.delay_ms(500);
}
}
// End of file