Merge #1340 #1474

1340: Add I2S for f4 r=Dirbaio a=xoviat

This is only for f4, but it puts us equal to or ahead of the standard rust hal.

1474: stm32: Fix watchdog timeout computation r=Dirbaio a=rmja



Co-authored-by: xoviat <xoviat@users.noreply.github.com>
Co-authored-by: Rasmus Melchior Jacobsen <rmja@laesoe.org>

examples/stm32f4/src/bin/i2s_dma.rs

@@ -0,0 +1,36 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use core::fmt::Write;
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_stm32::i2s::{Config, I2S};
+use embassy_stm32::time::Hertz;
+use heapless::String;
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_stm32::init(Default::default());
+    info!("Hello World!");
+
+    let mut i2s = I2S::new(
+        p.SPI2,
+        p.PC3,  // sd
+        p.PB12, // ws
+        p.PB10, // ck
+        p.PC6,  // mck
+        p.DMA1_CH4,
+        p.DMA1_CH3,
+        Hertz(1_000_000),
+        Config::default(),
+    );
+
+    for n in 0u32.. {
+        let mut write: String<128> = String::new();
+        core::write!(&mut write, "Hello DMA World {}!\r\n", n).unwrap();
+        i2s.write(&mut write.as_bytes()).await.ok();
+    }
+}