#![no_std]
#![no_main]

// We need to use cortex_m here so the linker can find it's critical-section, but we import is as
// an underscore since we don't directly use any of its symbols.
extern crate cortex_m;

// The entry import gives us a macro to indicate where the microcontroller should start the
// program, and also sets up the FPU on our Cortex-M4F.
use cortex_m_rt::entry;

use hal::{pac, prelude::*, rcc::Config};
// Provides functions that allow printing back to probe-rs.
use panic_rtt_target as _;
// use rtt_target::{rprintln, rtt_init_print};

// Start here, and don't ever return from this function.
#[entry]
fn main() -> ! {
    let dp = pac::Peripherals::take().unwrap();

    // Configure the clock.
    let mut rcc = dp.RCC.freeze(Config::hsi16());

    // Acquire the GPIOA peripheral. This also enables the clock for GPIOA in
    // the RCC register.
    let gpioa = dp.GPIOA.split(&mut rcc);

    // Configure PA1 as output.
    let mut led = gpioa.pa3.into_push_pull_output();

    loop {
        // Set the LED high one million times in a row.
        for _ in 0..1_000_000 {
            led.set_high().unwrap();
        }

        // Set the LED low one million times in a row.
        for _ in 0..1_000_000 {
            led.set_low().unwrap();
        }
    }
}