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Add fancier SysTick exception example moving the data into the exception handler

Signed-off-by: Daniel Egger <daniel@eggers-club.de>
trying.tmp
Daniel Egger 3 years ago
parent
commit
d5568bef8c
  1. 96
      examples/flash_systick_fancier.rs

96
examples/flash_systick_fancier.rs

@ -0,0 +1,96 @@
#![no_main]
#![no_std]
#[allow(unused)]
use panic_halt;
use stm32f0xx_hal as hal;
use crate::hal::{gpio::*, prelude::*, stm32};
use cortex_m::{interrupt::Mutex, peripheral::syst::SystClkSource::Core, Peripherals};
use cortex_m_rt::{entry, exception};
use core::cell::RefCell;
// A type definition for the GPIO pin to be used for our LED
type LEDPIN = gpiob::PB3<Output<PushPull>>;
// Mutex protected structure for our shared GPIO pin
static GPIO: Mutex<RefCell<Option<LEDPIN>>> = Mutex::new(RefCell::new(None));
#[entry]
fn main() -> ! {
if let (Some(mut p), Some(cp)) = (stm32::Peripherals::take(), Peripherals::take()) {
cortex_m::interrupt::free(move |cs| {
let mut rcc = p.RCC.configure().sysclk(48.mhz()).freeze(&mut p.FLASH);
// Get access to individual pins in the GPIO port
let gpioa = p.GPIOB.split(&mut rcc);
// (Re-)configure the pin connected to our LED as output
let led = gpioa.pb3.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() -> ! {
// Our moved LED pin
static mut LED: Option<LEDPIN> = None;
// Exception handler state variable
static mut STATE: u8 = 1;
// If LED pin was moved into the exception handler, just use it
if let Some(led) = LED {
// 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();
// And now increment state variable
*STATE += 1;
} else {
// Turn on the LED
led.set_high();
// And set new state variable back to 0
*STATE = 0;
}
}
// Otherwise move it out of the Mutex protected shared region into our exception handler
else {
// Enter critical section
cortex_m::interrupt::free(|cs| {
// Move LED pin here, leaving a None in its place
LED.replace(GPIO.borrow(cs).replace(None).unwrap());
});
}
}
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