examples/blinky_timer_irq.rs: added an '#[interrupt]' blinky demo

Cargo.toml

@@ -114,3 +114,8 @@ required-features = ["rt", "stm32f103", "stm32-usbd"]
 [[example]]
 name = "usb_serial_rtfm"
 required-features = ["rt", "stm32f103", "stm32-usbd"]
+
+[[example]]
+name = "blinky_timer_irq"
+required-features = ["medium", "rt", "stm32f103"]
+

examples/blinky_timer_irq.rs

@@ -0,0 +1,116 @@
+// blinky timer using interrupts on TIM2
+//
+// This demo based off of the following demo:
+// - https://github.com/stm32-rs/stm32f0xx-hal/blob/master/examples/blinky_timer_irq.rs
+// with some information about STM32F1 interrupts/peripherals from:
+// - https://github.com/geomatsi/rust-blue-pill-tests/blob/master/src/bin/blink-timer-irq-safe.rs
+
+#![no_main]
+#![no_std]
+
+use panic_halt as _;
+
+use stm32f1xx_hal as hal;
+
+use crate::hal::{
+    gpio::*,
+    prelude::*,
+    stm32::{interrupt, Interrupt, Peripherals, TIM2},
+    timer::*,
+};
+
+use core::cell::RefCell;
+use cortex_m::{
+    asm::wfi,
+    interrupt::Mutex,
+    peripheral::Peripherals as c_m_Peripherals};
+use cortex_m_rt::entry;
+
+// NOTE You can uncomment 'hprintln' here and in the code below for a bit more
+// verbosity at runtime, at the cost of throwing off the timing of the blink
+// (using 'semihosting' for printing debug info anywhere slows program
+// execution down)
+//use cortex_m_semihosting::hprintln;
+
+// A type definition for the GPIO pin to be used for our LED
+type LEDPIN = gpioc::PC13<Output<PushPull>>;
+
+// Make LED pin globally available
+static G_LED: Mutex<RefCell<Option<LEDPIN>>> = Mutex::new(RefCell::new(None));
+
+// Make timer interrupt registers globally available
+static G_TIM: Mutex<RefCell<Option<CountDownTimer<TIM2>>>> = Mutex::new(RefCell::new(None));
+
+// Define an interupt handler, i.e. function to call when interrupt occurs.
+// This specific interrupt will "trip" when the timer TIM2 times out
+#[interrupt]
+fn TIM2() {
+    static mut LED: Option<LEDPIN> = None;
+    static mut TIM: Option<CountDownTimer<TIM2>> = None;
+
+    let led = LED.get_or_insert_with(|| {
+        cortex_m::interrupt::free(|cs| {
+            // Move LED pin here, leaving a None in its place
+            G_LED.borrow(cs).replace(None).unwrap()
+        })
+    });
+
+    let tim = TIM.get_or_insert_with(|| {
+        cortex_m::interrupt::free(|cs| {
+            // Move LED pin here, leaving a None in its place
+            G_TIM.borrow(cs).replace(None).unwrap()
+        })
+    });
+
+    //hprintln!("TIM2 IRQ fired").unwrap();
+    led.toggle().ok();
+    tim.wait().ok();
+}
+
+#[entry]
+fn main() -> ! {
+    if let (Some(dp), Some(cp)) = (Peripherals::take(), c_m_Peripherals::take()) {
+        cortex_m::interrupt::free(move |cs| {
+            let mut rcc = dp.RCC.constrain();
+            let mut flash = dp.FLASH.constrain();
+            let clocks = rcc
+                .cfgr
+                .sysclk(8.mhz())
+                .pclk1(8.mhz())
+                .freeze(&mut flash.acr);
+
+            // configure PC13 pin to blink LED
+            let mut gpioc = dp.GPIOC.split(&mut rcc.apb2);
+            let led = gpioc.pc13.into_push_pull_output(&mut gpioc.crh);
+
+            // Move the pin into our global storage
+            *G_LED.borrow(cs).borrow_mut() = Some(led);
+
+            // Set up a timer expiring after 1s
+            let mut timer = Timer::tim2(dp.TIM2, &clocks, &mut rcc.apb1).start_count_down(1.hz());
+
+            // Generate an interrupt when the timer expires
+            timer.listen(Event::Update);
+
+            // Move the timer into our global storage
+            *G_TIM.borrow(cs).borrow_mut() = Some(timer);
+
+            // Enable TIM2 IRQ, set prio 1 and clear any pending IRQs
+            let mut nvic = cp.NVIC;
+            // calling 'set_priority()' and 'unmask()' requires 'unsafe {}'
+            // - https://docs.rs/stm32f1xx-hal/0.5.3/stm32f1xx_hal/stm32/struct.NVIC.html#method.set_priority
+            unsafe {
+                nvic.set_priority(Interrupt::TIM2, 1);
+                cortex_m::peripheral::NVIC::unmask(Interrupt::TIM2);
+            }
+            // Clear the interrupt state
+            cortex_m::peripheral::NVIC::unpend(Interrupt::TIM2);
+        });
+    }
+
+    //hprintln!("Entering main loop...").unwrap();
+    loop {
+        // from 'cortex_m::asm::wfi'
+        wfi();
+    }
+}