Fix nrf monotonics (#852)

* Fix nrf::timer

* Bootstrap nrf52840-blinky example

* More work on nrf blinky example

* Fix README

* Add asserts for correct timer functionality

* Add correctness check to other monotonics as well

* Update Changelog

* Fix potential timing issues

* Fix race condition in nrf::rtc

* Add changelog

* Add rtc blinky example

* Change rtc example to RC lf clock source

* Add changelog to rtic-time

* Add changelog

* Attempt to fix CI

* Update teensy4-blinky Cargo.lock

examples/nrf52840_blinky/src/bin/blinky_rtc.rs

@@ -0,0 +1,69 @@
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+#![feature(type_alias_impl_trait)]
+
+use nrf52840_blinky::hal;
+
+#[rtic::app(device = hal::pac, dispatchers = [SWI0_EGU0])]
+mod app {
+    use super::*;
+
+    use hal::gpio::{Level, Output, Pin, PushPull};
+    use hal::prelude::*;
+
+    use rtic_monotonics::nrf::rtc::Rtc0 as Mono;
+    use rtic_monotonics::nrf::rtc::*;
+    use rtic_monotonics::Monotonic;
+
+    #[shared]
+    struct Shared {}
+
+    #[local]
+    struct Local {
+        led: Pin<Output<PushPull>>,
+    }
+
+    #[init]
+    fn init(cx: init::Context) -> (Shared, Local) {
+        // Configure low frequency clock
+        hal::clocks::Clocks::new(cx.device.CLOCK).start_lfclk();
+
+        // Initialize Monotonic
+        let token = rtic_monotonics::create_nrf_rtc0_monotonic_token!();
+        Mono::start(cx.device.RTC0, token);
+
+        // Setup LED
+        let port0 = hal::gpio::p0::Parts::new(cx.device.P0);
+        let led = port0.p0_06.into_push_pull_output(Level::Low).degrade();
+
+        // Schedule the blinking task
+        blink::spawn().ok();
+
+        (Shared {}, Local { led })
+    }
+
+    #[task(local = [led])]
+    async fn blink(cx: blink::Context) {
+        let blink::LocalResources { led, .. } = cx.local;
+
+        let mut next_tick = Mono::now();
+        let mut blink_on = false;
+        loop {
+            let now = Mono::now();
+            let now_ms: fugit::SecsDurationU64 = now.duration_since_epoch().convert();
+            defmt::println!("Timer {} ({})", now_ms, now.ticks());
+
+            blink_on = !blink_on;
+            if blink_on {
+                led.set_high().unwrap();
+            } else {
+                led.set_low().unwrap();
+            }
+
+            next_tick += 1000.millis();
+            Mono::delay_until(next_tick).await;
+        }
+    }
+}

examples/nrf52840_blinky/src/bin/blinky_timer.rs

@@ -0,0 +1,66 @@
+#![deny(unsafe_code)]
+#![deny(warnings)]
+#![no_main]
+#![no_std]
+#![feature(type_alias_impl_trait)]
+
+use nrf52840_blinky::hal;
+
+#[rtic::app(device = hal::pac, dispatchers = [SWI0_EGU0])]
+mod app {
+    use super::*;
+
+    use hal::gpio::{Level, Output, Pin, PushPull};
+    use hal::prelude::*;
+
+    use rtic_monotonics::nrf::timer::Timer0 as Mono;
+    use rtic_monotonics::nrf::timer::*;
+    use rtic_monotonics::Monotonic;
+
+    #[shared]
+    struct Shared {}
+
+    #[local]
+    struct Local {
+        led: Pin<Output<PushPull>>,
+    }
+
+    #[init]
+    fn init(cx: init::Context) -> (Shared, Local) {
+        // Initialize Monotonic
+        let token = rtic_monotonics::create_nrf_timer0_monotonic_token!();
+        Mono::start(cx.device.TIMER0, token);
+
+        // Setup LED
+        let port0 = hal::gpio::p0::Parts::new(cx.device.P0);
+        let led = port0.p0_06.into_push_pull_output(Level::Low).degrade();
+
+        // Schedule the blinking task
+        blink::spawn().ok();
+
+        (Shared {}, Local { led })
+    }
+
+    #[task(local = [led])]
+    async fn blink(cx: blink::Context) {
+        let blink::LocalResources { led, .. } = cx.local;
+
+        let mut next_tick = Mono::now();
+        let mut blink_on = false;
+        loop {
+            let now = Mono::now();
+            let now_ms: fugit::SecsDurationU64 = now.duration_since_epoch().convert();
+            defmt::println!("Timer {} ({})", now_ms, now.ticks());
+
+            blink_on = !blink_on;
+            if blink_on {
+                led.set_high().unwrap();
+            } else {
+                led.set_low().unwrap();
+            }
+
+            next_tick += 1000.millis();
+            Mono::delay_until(next_tick).await;
+        }
+    }
+}

examples/nrf52840_blinky/src/lib.rs

@@ -0,0 +1,37 @@
+#![no_main]
+#![no_std]
+
+use cortex_m_semihosting::debug;
+
+use defmt_rtt as _; // global logger
+
+pub use nrf52840_hal as hal; // memory layout
+
+use panic_probe as _;
+
+// same panicking *behavior* as `panic-probe` but doesn't print a panic message
+// this prevents the panic message being printed *twice* when `defmt::panic` is invoked
+#[defmt::panic_handler]
+fn panic() -> ! {
+    cortex_m::asm::udf()
+}
+
+/// Terminates the application and makes a semihosting-capable debug tool exit
+/// with status code 0.
+pub fn exit() -> ! {
+    loop {
+        debug::exit(debug::EXIT_SUCCESS);
+    }
+}
+
+/// Hardfault handler.
+///
+/// Terminates the application and makes a semihosting-capable debug tool exit
+/// with an error. This seems better than the default, which is to spin in a
+/// loop.
+#[cortex_m_rt::exception]
+unsafe fn HardFault(_frame: &cortex_m_rt::ExceptionFrame) -> ! {
+    loop {
+        debug::exit(debug::EXIT_FAILURE);
+    }
+}