Merge #678

678: Add minimal F2 family support r=Dirbaio a=Gekkio

Here's the bare minimum to support F2 family (207/217/205/215). A lot is missing in RCC (e.g. PLL support), but this is enough to have a working blinky example. The example is set up for a NUCLEO-F207ZG board which I don't have, but I've tested it on my custom board with a F215 and different pinout :sweat_smile: 

After looking at other RCC implementation, I noticed there's two main API styles: a "low-level" API (e.g. L0) where the `Config` struct has dividers and other low-level "knobs", and a "high-level" API (e.g. F0) where it has desired clock frequencies and the RCC implementation figures out how to achieve them. Which one is preferred? Personally I like the low-level API slightly more, because it gives you the most control and it would be easy to also provide some functions to calculate the required parameters based on desired clock frequencies.

F2 has a nasty errata: a delay or DSB instruction must be added after every RCC peripheral clock enable. I've added this workaround to build.rs, but am not sure if this is the best approach. Any comments?

I'm planning to add PLL support too once I know which kind of API is preferred. Would you prefer a separate pull request for that, or should I continue working on this one?

Co-authored-by: Joonas Javanainen <[email protected]>

5 files changed, 80 insertions, 0 deletions

diff --git a/examples/stm32f2/.cargo/config b/examples/stm32f2/.cargo/config
new file mode 100644
index 000000000..30b6d1909
--- /dev/null
+++ b/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"
diff --git a/examples/stm32f2/Cargo.toml b/examples/stm32f2/Cargo.toml
new file mode 100644
index 000000000..ee1d7ce2b
--- /dev/null
+++ b/examples/stm32f2/Cargo.toml
@@ -0,0 +1,21 @@
+[package]
+authors = ["Dario Nieuwenhuis <[email protected]>"]
+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"
diff --git a/examples/stm32f2/build.rs b/examples/stm32f2/build.rs
new file mode 100644
index 000000000..8cd32d7ed
--- /dev/null
+++ b/examples/stm32f2/build.rs
@@ -0,0 +1,5 @@
+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");
+}
diff --git a/examples/stm32f2/src/bin/blinky.rs b/examples/stm32f2/src/bin/blinky.rs
new file mode 100644
index 000000000..637c2f4fd
--- /dev/null
+++ b/examples/stm32f2/src/bin/blinky.rs
@@ -0,0 +1,29 @@
+#![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;
+    }
+}
diff --git a/examples/stm32f2/src/example_common.rs b/examples/stm32f2/src/example_common.rs
new file mode 100644
index 000000000..e14517033
--- /dev/null
+++ b/examples/stm32f2/src/example_common.rs
@@ -0,0 +1,19 @@
+#![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
+    }
+}