Add raw_spawn example, showcasing how to use embassy without TAIT

embassy-nrf-examples/src/bin/raw_spawn.rs

@@ -0,0 +1,73 @@
+#![no_std]
+#![no_main]
+
+#[path = "../example_common.rs"]
+mod example_common;
+use core::mem;
+
+use embassy::executor::raw::Task;
+use example_common::*;
+
+use cortex_m_rt::entry;
+use defmt::panic;
+use embassy::executor::Executor;
+use embassy::time::{Duration, Timer};
+use embassy::util::Forever;
+use embassy_nrf::pac;
+use embassy_nrf::{interrupt, rtc};
+use nrf52840_hal::clocks;
+
+async fn run1() {
+    loop {
+        info!("BIG INFREQUENT TICK");
+        Timer::after(Duration::from_ticks(64000)).await;
+    }
+}
+
+async fn run2() {
+    loop {
+        info!("tick");
+        Timer::after(Duration::from_ticks(13000)).await;
+    }
+}
+
+static RTC: Forever<rtc::RTC<pac::RTC1>> = Forever::new();
+static ALARM: Forever<rtc::Alarm<pac::RTC1>> = Forever::new();
+static EXECUTOR: Forever<Executor> = Forever::new();
+
+#[entry]
+fn main() -> ! {
+    info!("Hello World!");
+
+    let p = unwrap!(embassy_nrf::pac::Peripherals::take());
+
+    clocks::Clocks::new(p.CLOCK)
+        .enable_ext_hfosc()
+        .set_lfclk_src_external(clocks::LfOscConfiguration::NoExternalNoBypass)
+        .start_lfclk();
+
+    let rtc = RTC.put(rtc::RTC::new(p.RTC1, interrupt::take!(RTC1)));
+    rtc.start();
+
+    unsafe { embassy::time::set_clock(rtc) };
+
+    let alarm = ALARM.put(rtc.alarm0());
+    let executor = EXECUTOR.put(Executor::new());
+    executor.set_alarm(alarm);
+
+    let run1_task = Task::new();
+    let run2_task = Task::new();
+
+    // Safety: these variables do live forever if main never returns.
+    let run1_task = unsafe { make_static(&run1_task) };
+    let run2_task = unsafe { make_static(&run2_task) };
+
+    executor.run(|spawner| {
+        unwrap!(spawner.spawn(run1_task.spawn(|| run1())));
+        unwrap!(spawner.spawn(run2_task.spawn(|| run2())));
+    });
+}
+
+unsafe fn make_static<T>(t: &T) -> &'static T {
+    mem::transmute(t)
+}