hello_stm32f401.rs

#![no_std]
#![no_main]

use cortex_m_rt::entry;
use cortex_m_semihosting::hprintln;
use panic_semihosting as _;

use stm32f4::stm32f401::Peripherals;

fn init_board() -> Peripherals {
    // LED on PA5
    // Button on PC13

    let p = Peripherals::take().unwrap();

    let rcc = &p.RCC;
    let pa = &p.GPIOA;
    let pc = &p.GPIOC;

    rcc.ahb1enr
        .modify(|_, w| w.gpioaen().enabled().gpiocen().enabled());
    pa.moder.modify(|_, w| w.moder5().output());
    pc.moder.modify(|_, w| w.moder13().input());

    p
}

fn toggle_led(p: &Peripherals) {
    p.GPIOA.odr.modify(|r, w| w.odr5().bit(!r.odr5().bit()));
}

#[entry]
fn main() -> ! {
    hprintln!("Hello, world!");

    let p = init_board();
    toggle_led(&p);
    toggle_led(&p);
    toggle_led(&p);
    toggle_led(&p);

    hprintln!("Goodbye!");

    loop {}
}