#![no_std]
    #![no_main]

    /**** low-level imports *****/
    use core::fmt::Write;
    use core::panic::PanicInfo;
    // use panic_halt as _;
    // use cortex_m::prelude::*;
    use cortex_m_rt::entry;
    use embedded_hal::{
        digital::v2::{OutputPin},
    };

    /***** board-specific imports *****/
    use adafruit_feather_rp2040::hal as hal;
    use hal::{
        pac::interrupt,
        clocks::{init_clocks_and_plls, Clock},
        pac,
        watchdog::Watchdog,
        Sio,
    };
    use adafruit_feather_rp2040::{
        Pins, XOSC_CRYSTAL_FREQ,
    };

    #[panic_handler]
    fn panic(panic_info: &PanicInfo) -> ! {
        loop {}
    }

    #[entry]
    fn main() -> ! {
        // Grab the singleton objects
        let mut pac = pac::Peripherals::take().unwrap();
        let core = pac::CorePeripherals::take().unwrap();
        // Init the watchdog timer, to pass into the clock init
        let mut watchdog = Watchdog::new(pac.WATCHDOG);
        let clocks = init_clocks_and_plls(
            XOSC_CRYSTAL_FREQ,
            pac.XOSC,
            pac.CLOCKS,
            pac.PLL_SYS,
            pac.PLL_USB,
            &mut pac.RESETS,
            &mut watchdog,
        ).ok().unwrap();

        // initialize the Single Cycle IO
        let sio = Sio::new(pac.SIO);
        // initialize the pins to default state
        let pins = Pins::new(
            pac.IO_BANK0,
            pac.PADS_BANK0,
            sio.gpio_bank0,
            &mut pac.RESETS,
        );

        let mut timer = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().to_Hz());
        let mut led_pin = pins.d13.into_push_pull_output();

        /*
        Loop Section
        */
        let delay: u32 = 500;   // loop delay in ms
        let mut n: u32 = 0;
        loop {
            led_pin.set_low().unwrap();
            timer.delay_ms(delay as u32);
            led_pin.set_high().unwrap();
            timer.delay_ms(delay as u32);
            n = n + 1;
        }

    }