//! Blinks an LED
//!
//! This assumes that a LED is connected to pc13 as is the case on the blue pill board.
//!
//! Note: Without additional hardware, PC13 should not be used to drive an LED, see page 5.1.2 of
//! the reference manual for an explanation. This is not an issue on the blue pill.

#![deny(unsafe_code)]
#![no_std]
#![no_main]

use panic_halt as _;

use core::hint::spin_loop;
use cortex_m_rt::entry;
use embedded_hal::digital::OutputPin;
use gd32f1x0_hal::{pac, prelude::*, timer::Timer};

#[entry]
fn main() -> ! {
    // Get access to the core peripherals from the cortex-m crate
    let cp = cortex_m::Peripherals::take().unwrap();
    // Get access to the device specific peripherals from the peripheral access crate
    let dp = pac::Peripherals::take().unwrap();

    // Take ownership over the raw rcu and flash devices and convert them into the corresponding HAL
    // structs.
    let mut flash = dp.fmc.constrain();
    let mut rcu = dp.rcu.constrain();

    // Freeze the configuration of all the clocks in the system and store the frozen frequencies in
    // `clocks`
    let clocks = rcu.cfgr.freeze(&mut flash.ws);

    // Acquire the GPIOC peripheral
    let mut gpioc = dp.gpioc.split(&mut rcu.ahb);

    // Configure gpio C pin 13 as a push-pull output. The `crh` register is passed to the function
    // in order to configure the port. For pins 0-7, crl should be passed instead.
    let mut led = gpioc.pc13.into_push_pull_output(&mut gpioc.config);
    // Configure the syst timer to trigger an update every second
    let mut timer = Timer::syst(cp.SYST, &clocks).start_count_down(1.hz());

    // Wait for the timer to trigger an update and change the state of the LED
    loop {
        while !timer.has_elapsed() {
            spin_loop();
        }
        led.set_high().unwrap();
        while !timer.has_elapsed() {
            spin_loop();
        }
        led.set_low().unwrap();
    }
}