Add adapter for implementing async traits for blocking types

This allows writing drivers relying on async traits, while still
functioning with implementations that already implement the embedded-hal
traits.

Add examples to stm32l4 for using this feature.

examples/stm32l4/src/bin/i2c_blocking_async.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_stm32::dma::NoDma;
+use embassy_stm32::i2c::I2c;
+use embassy_stm32::interrupt;
+use embassy_stm32::time::Hertz;
+use embassy_stm32::Peripherals;
+use embassy_traits::{adapter::BlockingAsync, i2c::I2c as _};
+use example_common::{info, unwrap};
+
+const ADDRESS: u8 = 0x5F;
+const WHOAMI: u8 = 0x0F;
+
+#[embassy::main]
+async fn main(_spawner: Spawner, p: Peripherals) -> ! {
+    let irq = interrupt::take!(I2C2_EV);
+    let i2c = I2c::new(p.I2C2, p.PB10, p.PB11, irq, NoDma, NoDma, Hertz(100_000));
+    let mut i2c = BlockingAsync::new(i2c);
+
+    let mut data = [0u8; 1];
+    unwrap!(i2c.write_read(ADDRESS, &[WHOAMI], &mut data).await);
+    info!("Whoami: {}", data[0]);
+}

examples/stm32l4/src/bin/spi_blocking_async.rs

@@ -0,0 +1,57 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+#[path = "../example_common.rs"]
+mod example_common;
+
+use embassy::executor::Spawner;
+use embassy_stm32::dma::NoDma;
+use embassy_stm32::gpio::{Input, Level, Output, Pull, Speed};
+use embassy_stm32::spi::{Config, Spi};
+use embassy_stm32::time::Hertz;
+use embassy_stm32::Peripherals;
+use embassy_traits::{adapter::BlockingAsync, spi::FullDuplex};
+use embedded_hal::digital::v2::{InputPin, OutputPin};
+use example_common::*;
+
+#[embassy::main]
+async fn main(_spawner: Spawner, p: Peripherals) {
+    info!("Hello World!");
+
+    let spi = Spi::new(
+        p.SPI3,
+        p.PC10,
+        p.PC12,
+        p.PC11,
+        NoDma,
+        NoDma,
+        Hertz(1_000_000),
+        Config::default(),
+    );
+
+    let mut spi = BlockingAsync::new(spi);
+
+    // These are the pins for the Inventek eS-Wifi SPI Wifi Adapter.
+
+    let _boot = Output::new(p.PB12, Level::Low, Speed::VeryHigh);
+    let _wake = Output::new(p.PB13, Level::Low, Speed::VeryHigh);
+    let mut reset = Output::new(p.PE8, Level::Low, Speed::VeryHigh);
+    let mut cs = Output::new(p.PE0, Level::High, Speed::VeryHigh);
+    let ready = Input::new(p.PE1, Pull::Up);
+
+    cortex_m::asm::delay(100_000);
+    unwrap!(reset.set_high());
+    cortex_m::asm::delay(100_000);
+
+    while unwrap!(ready.is_low()) {
+        info!("waiting for ready");
+    }
+
+    let write = [0x0A; 10];
+    let mut read = [0; 10];
+    unwrap!(cs.set_low());
+    spi.read_write(&mut read, &write).await.ok();
+    unwrap!(cs.set_high());
+    info!("xfer {=[u8]:x}", read);
+}

examples/stm32l4/src/bin/usart_blocking_async.rs

@@ -0,0 +1,32 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+#[path = "../example_common.rs"]
+mod example_common;
+
+use embassy::executor::Spawner;
+use embassy::traits::{
+    adapter::BlockingAsync,
+    uart::{Read, Write},
+};
+use embassy_stm32::dma::NoDma;
+use embassy_stm32::usart::{Config, Uart};
+use embassy_stm32::Peripherals;
+use example_common::*;
+
+#[embassy::main]
+async fn main(_spawner: Spawner, p: Peripherals) {
+    let config = Config::default();
+    let usart = Uart::new(p.UART4, p.PA1, p.PA0, NoDma, NoDma, config);
+    let mut usart = BlockingAsync::new(usart);
+
+    unwrap!(usart.write(b"Hello Embassy World!\r\n").await);
+    info!("wrote Hello, starting echo");
+
+    let mut buf = [0u8; 1];
+    loop {
+        unwrap!(usart.read(&mut buf).await);
+        unwrap!(usart.write(&buf).await);
+    }
+}