esp-hal/esp32s2-hal/examples/clock_monitor.rs

//! This demos a simple monitor for the XTAL frequency, by relying on a special
//! feature of the TIMG0 (Timer Group 0). This feature counts the number of XTAL
//! clock cycles within a given number of RTC_SLOW_CLK cycles.

#![no_std]
#![no_main]

use core::cell::RefCell;

use esp32s2_hal::{
    clock::ClockControl,
    interrupt,
    pac::{self, Peripherals},
    prelude::*,
    Rtc,
};
use panic_halt as _;
use xtensa_lx::mutex::{CriticalSectionMutex, Mutex};
use xtensa_lx_rt::entry;

static mut RTC: CriticalSectionMutex<RefCell<Option<Rtc>>> =
    CriticalSectionMutex::new(RefCell::new(None));

#[entry]
fn main() -> ! {
    let peripherals = Peripherals::take().unwrap();
    let system = peripherals.SYSTEM.split();
    let clocks = ClockControl::boot_defaults(system.clock_control).freeze();

    let mut rtc = Rtc::new(peripherals.RTC_CNTL);

    // Disable watchdog timer
    rtc.rwdt.disable();

    rtc.rwdt.start(2000u64.millis());
    rtc.rwdt.listen();

    esp_println::println!(
        "{: <10} XTAL frequency: {} MHz",
        "[Expected]",
        clocks.xtal_clock.to_MHz()
    );

    interrupt::enable(pac::Interrupt::RTC_CORE, interrupt::Priority::Priority1).unwrap();

    unsafe {
        (&RTC).lock(|data| (*data).replace(Some(rtc)));
    }

    loop {}
}

#[interrupt]
fn RTC_CORE() {
    unsafe {
        (&RTC).lock(|data| {
            let mut rtc = data.borrow_mut();
            let rtc = rtc.as_mut().unwrap();

            esp_println::println!(
                "{: <10} XTAL frequency: {} MHz",
                "[Monitor]",
                rtc.estimate_xtal_frequency()
            );

            rtc.rwdt.clear_interrupt();
        });
    }
}