embassy/embassy-rp/src/watchdog.rs

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//! Watchdog
//!
//! The watchdog is a countdown timer that can restart parts of the chip if it reaches zero. This can be used to restart the
//! processor if software gets stuck in an infinite loop. The programmer must periodically write a value to the watchdog to
//! stop it from reaching zero.
//!
//! Credit: based on `rp-hal` implementation (also licensed Apache+MIT)
use core::marker::PhantomData;
use embassy_time::Duration;
use crate::pac;
use crate::peripherals::WATCHDOG;
/// Watchdog peripheral
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pub struct Watchdog {
phantom: PhantomData<WATCHDOG>,
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load_value: u32, // decremented by 2 per tick (µs)
}
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impl Watchdog {
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/// Create a new `Watchdog`
pub fn new(_watchdog: WATCHDOG) -> Self {
Self {
phantom: PhantomData,
load_value: 0,
}
}
/// Start tick generation on clk_tick which is driven from clk_ref.
///
/// # Arguments
///
/// * `cycles` - Total number of tick cycles before the next tick is generated.
/// It is expected to be the frequency in MHz of clk_ref.
pub fn enable_tick_generation(&mut self, cycles: u8) {
unsafe {
let watchdog = pac::WATCHDOG;
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watchdog.tick().write(|w| {
w.set_enable(true);
w.set_cycles(cycles.into())
});
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}
}
/// Defines whether or not the watchdog timer should be paused when processor(s) are in debug mode
/// or when JTAG is accessing bus fabric
pub fn pause_on_debug(&mut self, pause: bool) {
unsafe {
let watchdog = pac::WATCHDOG;
watchdog.ctrl().write(|w| {
w.set_pause_dbg0(pause);
w.set_pause_dbg1(pause);
w.set_pause_jtag(pause);
})
}
}
fn load_counter(&self, counter: u32) {
unsafe {
let watchdog = pac::WATCHDOG;
watchdog.load().write_value(pac::watchdog::regs::Load(counter));
}
}
fn enable(&self, bit: bool) {
unsafe {
let watchdog = pac::WATCHDOG;
watchdog.ctrl().write(|w| w.set_enable(bit))
}
}
// Configure which hardware will be reset by the watchdog
// (everything except ROSC, XOSC)
unsafe fn configure_wdog_reset_triggers(&self) {
let psm = pac::PSM;
psm.wdsel().write_value(pac::psm::regs::Wdsel(
0x0001ffff & !(0x01 << 0usize) & !(0x01 << 1usize),
));
}
/// Feed the watchdog timer
pub fn feed(&mut self) {
self.load_counter(self.load_value)
}
/// Start the watchdog timer
pub fn start(&mut self, period: Duration) {
const MAX_PERIOD: u32 = 0xFFFFFF;
let delay_us = period.as_micros() as u32;
if delay_us > MAX_PERIOD / 2 {
panic!(
"Period cannot exceed maximum load value of {} ({} microseconds))",
MAX_PERIOD,
MAX_PERIOD / 2
);
}
// Due to a logic error, the watchdog decrements by 2 and
// the load value must be compensated; see RP2040-E1
self.load_value = delay_us * 2;
self.enable(false);
unsafe {
self.configure_wdog_reset_triggers();
}
self.load_counter(self.load_value);
self.enable(true);
}
}