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use panic_halt as _;
use stm32f0xx_hal as hal;
use crate::hal::{
stm32::{interrupt, Interrupt, Peripherals, EXTI},
use cortex_m::{interrupt::Mutex, peripheral::Peripherals as c_m_Peripherals};
use cortex_m_rt::entry;
use core::{cell::RefCell, ops::DerefMut};
// Make our LED globally available
static LED: Mutex<RefCell<Option<gpioa::PA1<Output<PushPull>>>>> = Mutex::new(RefCell::new(None));
// Make our delay provider globally available
static DELAY: Mutex<RefCell<Option<Delay>>> = Mutex::new(RefCell::new(None));
// Make external interrupt registers globally available
static INT: Mutex<RefCell<Option<EXTI>>> = Mutex::new(RefCell::new(None));
fn main() -> ! {
if let (Some(p), Some(cp)) = (Peripherals::take(), c_m_Peripherals::take()) {
cortex_m::interrupt::free(move |cs| {
// Enable clock for SYSCFG
let rcc = p.RCC;
rcc.apb2enr.modify(|_, w| w.syscfgen().set_bit());
let mut flash = p.FLASH;
let mut rcc = rcc.configure().sysclk(8.mhz()).freeze(&mut flash);
let gpioa = p.GPIOA.split(&mut rcc);
let gpiob = p.GPIOB.split(&mut rcc);
let syscfg = p.SYSCFG;
let exti = p.EXTI;
// Configure PB1 as input (button)
let _ = gpiob.pb1.into_pull_down_input(cs);
// Configure PA1 as output (LED)
let mut led = gpioa.pa1.into_push_pull_output(cs);
// Turn off LED
// Initialise delay provider
let delay = Delay::new(cp.SYST, &rcc);
// Enable external interrupt for PB1
syscfg.exticr1.modify(|_, w| unsafe { w.exti1().bits(1) });
// Set interrupt request mask for line 1
exti.imr.modify(|_, w| w.mr1().set_bit());
// Set interrupt rising trigger for line 1
exti.rtsr.modify(|_, w| w.tr1().set_bit());
// Move control over LED and DELAY and EXTI into global mutexes
*LED.borrow(cs).borrow_mut() = Some(led);
*DELAY.borrow(cs).borrow_mut() = Some(delay);
*INT.borrow(cs).borrow_mut() = Some(exti);
// Enable EXTI IRQ, set prio 1 and clear any pending IRQs
let mut nvic = cp.NVIC;
unsafe {
nvic.set_priority(Interrupt::EXTI0_1, 1);
loop {
// Define an interupt handler, i.e. function to call when interrupt occurs. Here if our external
// interrupt trips when the button is pressed and will light the LED for a second
fn EXTI0_1() {
// Enter critical section
cortex_m::interrupt::free(|cs| {
// Obtain all Mutex protected resources
if let (&mut Some(ref mut led), &mut Some(ref mut delay), &mut Some(ref mut exti)) = (
) {
// Turn on LED
// Wait a second
// Turn off LED
// Clear event triggering the interrupt|w| w.pif1().set_bit());