GPOUT on gpio25 on pico

main.rs

#![no_std]
#![no_main]

use defmt::*;
use defmt_rtt as _;
use panic_probe as _;
use rp2040_hal::{
    clocks::{init_clocks_and_plls, Clock},
    entry,
    gpio::FunctionClock,
    pac,
    sio::Sio,
    timer::Timer,
    watchdog::Watchdog,
};

use embedded_hal::delay::DelayNs;
use rp2040_hal as hal;
use rp2040_hal::fugit::RateExtU32;

#[link_section = ".boot2"]
#[used]
pub static BOOT2: [u8; 256] = rp2040_boot2::BOOT_LOADER_GENERIC_03H;

#[entry]
fn main() -> ! {
    info!("Program start");
    let mut pac = pac::Peripherals::take().unwrap();
    let _core = pac::CorePeripherals::take().unwrap();
    let mut watchdog = Watchdog::new(pac.WATCHDOG);
    let sio = Sio::new(pac.SIO);

    // External high-speed crystal on the pico board is 12Mhz
    let external_xtal_freq_hz = 12_000_000u32;
    let mut clocks = init_clocks_and_plls(
        external_xtal_freq_hz,
        pac.XOSC,
        pac.CLOCKS,
        pac.PLL_SYS,
        pac.PLL_USB,
        &mut pac.RESETS,
        &mut watchdog,
    )
    .ok()
    .unwrap();

    let pins = hal::gpio::Pins::new(
        pac.IO_BANK0,
        pac.PADS_BANK0,
        sio.gpio_bank0,
        &mut pac.RESETS,
    );

    let mut delay = Timer::new(pac.TIMER, &mut pac.RESETS, &clocks);

    clocks
        .gpio_output3_clock
        .configure_clock(&clocks.system_clock, 8.Hz())
        .unwrap();

    let _led = pins
        .gpio25
        .into_push_pull_output()
        .into_function::<FunctionClock>();

    info!("all important logic is done, now we just output a square wave all day");
    loop {
        delay.delay_ms(500);
    }
}