Add blinky example for STM32F2

Default configuration is for NUCLEO-F207ZG board

examples/stm32f2/.cargo/config

@@ -0,0 +1,6 @@
+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+# replace STM32F207ZGTx with your chip as listed in `probe-run --list-chips`
+runner = "probe-run --chip STM32F207ZGTx"
+
+[build]
+target = "thumbv7m-none-eabi"

examples/stm32f2/Cargo.toml

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+[package]
+authors = ["Dario Nieuwenhuis <dirbaio@dirbaio.net>"]
+edition = "2018"
+name = "embassy-stm32f2-examples"
+version = "0.1.0"
+resolver = "2"
+
+[dependencies]
+embassy = { version = "0.1.0", path = "../../embassy", features = ["defmt"] }
+embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "defmt", "stm32f207zg", "unstable-pac", "memory-x", "time-driver-any", "exti"]  }
+
+defmt = "0.3"
+defmt-rtt = "0.3"
+
+cortex-m = "0.7.3"
+cortex-m-rt = "0.7.0"
+embedded-hal = "0.2.6"
+panic-probe = { version = "0.3", features = ["print-defmt"] }
+futures = { version = "0.3.17", default-features = false, features = ["async-await"] }
+heapless = { version = "0.7.5", default-features = false }
+nb = "1.0.0"

examples/stm32f2/build.rs

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+fn main() {
+    println!("cargo:rustc-link-arg-bins=--nmagic");
+    println!("cargo:rustc-link-arg-bins=-Tlink.x");
+    println!("cargo:rustc-link-arg-bins=-Tdefmt.x");
+}

examples/stm32f2/src/bin/blinky.rs

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+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+#[path = "../example_common.rs"]
+mod example_common;
+
+use embassy::executor::Spawner;
+use embassy::time::{Duration, Timer};
+use embassy_stm32::gpio::{Level, Output, Speed};
+use embassy_stm32::Peripherals;
+use example_common::*;
+
+#[embassy::main]
+async fn main(_spawner: Spawner, p: Peripherals) {
+    info!("Hello World!");
+
+    let mut led = Output::new(p.PB14, Level::High, Speed::Low);
+
+    loop {
+        info!("high");
+        led.set_high();
+        Timer::after(Duration::from_millis(1000)).await;
+
+        info!("low");
+        led.set_low();
+        Timer::after(Duration::from_millis(1000)).await;
+    }
+}

examples/stm32f2/src/example_common.rs

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+#![macro_use]
+
+use defmt_rtt as _; // global logger
+use panic_probe as _;
+
+pub use defmt::*;
+
+use core::sync::atomic::{AtomicUsize, Ordering};
+
+defmt::timestamp! {
+    "{=u64}",
+    {
+        static COUNT: AtomicUsize = AtomicUsize::new(0);
+        // NOTE(no-CAS) `timestamps` runs with interrupts disabled
+        let n = COUNT.load(Ordering::Relaxed);
+        COUNT.store(n + 1, Ordering::Relaxed);
+        n as u64
+    }
+}