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#![no_main]
#![no_std]
use panic_halt as _;
use stm32f0xx_hal as hal;
use crate::hal::{gpio::*, pac, prelude::*};
use cortex_m::{interrupt::Mutex, peripheral::syst::SystClkSource::Core, Peripherals};
use cortex_m_rt::{entry, exception};
use core::cell::RefCell;
use core::ops::DerefMut;
// Mutex protected structure for our shared GPIO pin
static GPIO: Mutex<RefCell<Option<gpioa::PA1<Output<PushPull>>>>> = Mutex::new(RefCell::new(None));
#[entry]
fn main() -> ! {
if let (Some(mut p), Some(cp)) = (pac::Peripherals::take(), Peripherals::take()) {
cortex_m::interrupt::free(move |cs| {
let mut rcc = p.RCC.configure().sysclk(48.mhz()).freeze(&mut p.FLASH);
let gpioa = p.GPIOA.split(&mut rcc);
// (Re-)configure PA1 as output
let led = gpioa.pa1.into_push_pull_output(cs);
// Transfer GPIO into a shared structure
*GPIO.borrow(cs).borrow_mut() = Some(led);
let mut syst = cp.SYST;
// Initialise SysTick counter with a defined value
unsafe { syst.cvr.write(1) };
// Set source for SysTick counter, here full operating frequency (== 48MHz)
syst.set_clock_source(Core);
// Set reload value, i.e. timer delay 48 MHz/4 Mcounts == 12Hz or 83ms
syst.set_reload(4_000_000 - 1);
// Start counting
syst.enable_counter();
// Enable interrupt generation
syst.enable_interrupt();
});
}
loop {
continue;
}
}
// Define an exception handler, i.e. function to call when exception occurs. Here, if our SysTick
// timer generates an exception the following handler will be called
#[exception]
fn SysTick() {
// Exception handler state variable
static mut STATE: u8 = 1;
// Enter critical section
cortex_m::interrupt::free(|cs| {
// Borrow access to our GPIO pin from the shared structure
if let Some(ref mut led) = *GPIO.borrow(cs).borrow_mut().deref_mut() {
// Check state variable, keep LED off most of the time and turn it on every 10th tick
if *STATE < 10 {
// Turn off the LED
led.set_low().ok();
// And now increment state variable
*STATE += 1;
} else {
// Turn on the LED
led.set_high().ok();
// And set new state variable back to 0
*STATE = 0;
}
}
});
}