Add UART and DMA drivers

Both blocking and async versions are supported. Add separate examples
for each mode.

examples/mimxrt6/src/bin/uart-async.rs

@@ -0,0 +1,87 @@
+#![no_std]
+#![no_main]
+
+extern crate embassy_imxrt_examples;
+
+use defmt::info;
+use embassy_executor::Spawner;
+use embassy_imxrt::flexcomm::uart::{self, Async, Uart};
+use embassy_imxrt::{bind_interrupts, peripherals};
+use embassy_time::Timer;
+use {defmt_rtt as _, panic_probe as _};
+
+bind_interrupts!(struct Irqs {
+    FLEXCOMM2 => uart::InterruptHandler<peripherals::FLEXCOMM2>;
+    FLEXCOMM4 => uart::InterruptHandler<peripherals::FLEXCOMM4>;
+});
+
+const BUFLEN: usize = 16;
+
+#[embassy_executor::task]
+async fn usart4_task(mut uart: Uart<'static, Async>) {
+    info!("RX Task");
+
+    loop {
+        let mut rx_buf = [0; BUFLEN];
+        uart.read(&mut rx_buf).await.unwrap();
+        info!("usart4: rx_buf {:02x}", rx_buf);
+
+        Timer::after_millis(10).await;
+
+        let tx_buf = [0xaa; BUFLEN];
+        uart.write(&tx_buf).await.unwrap();
+        info!("usart4: tx_buf {:02x}", tx_buf);
+    }
+}
+
+#[embassy_executor::task]
+async fn usart2_task(mut uart: Uart<'static, Async>) {
+    info!("TX Task");
+
+    loop {
+        let tx_buf = [0x55; BUFLEN];
+        uart.write(&tx_buf).await.unwrap();
+        info!("usart2: tx_buf {:02x}", tx_buf);
+
+        Timer::after_millis(10).await;
+
+        let mut rx_buf = [0x00; BUFLEN];
+        uart.read(&mut rx_buf).await.unwrap();
+        info!("usart2: rx_buf {:02x}", rx_buf);
+    }
+}
+
+#[embassy_executor::main]
+async fn main(spawner: Spawner) {
+    let p = embassy_imxrt::init(Default::default());
+
+    info!("UART test start");
+
+    let usart4 = Uart::new_with_rtscts(
+        p.FLEXCOMM4,
+        p.PIO0_29,
+        p.PIO0_30,
+        p.PIO1_0,
+        p.PIO0_31,
+        Irqs,
+        p.DMA0_CH9,
+        p.DMA0_CH8,
+        Default::default(),
+    )
+    .unwrap();
+    spawner.must_spawn(usart4_task(usart4));
+
+    let usart2 = Uart::new_with_rtscts(
+        p.FLEXCOMM2,
+        p.PIO0_15,
+        p.PIO0_16,
+        p.PIO0_18,
+        p.PIO0_17,
+        Irqs,
+        p.DMA0_CH5,
+        p.DMA0_CH4,
+        Default::default(),
+    )
+    .unwrap();
+    spawner.must_spawn(usart2_task(usart2));
+}

examples/mimxrt6/src/bin/uart.rs

@@ -0,0 +1,55 @@
+#![no_std]
+#![no_main]
+
+extern crate embassy_imxrt_examples;
+
+use defmt::info;
+use embassy_executor::Spawner;
+use embassy_imxrt::flexcomm::uart::{Blocking, Uart, UartRx, UartTx};
+use embassy_time::Timer;
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::task]
+async fn usart4_task(mut uart: UartRx<'static, Blocking>) {
+    info!("RX Task");
+
+    loop {
+        let mut buf = [0; 8];
+
+        Timer::after_millis(10).await;
+
+        uart.blocking_read(&mut buf).unwrap();
+
+        let s = core::str::from_utf8(&buf).unwrap();
+
+        info!("Received '{}'", s);
+    }
+}
+
+#[embassy_executor::task]
+async fn usart2_task(mut uart: UartTx<'static, Blocking>) {
+    info!("TX Task");
+
+    loop {
+        let buf = "Testing\0".as_bytes();
+
+        uart.blocking_write(buf).unwrap();
+
+        Timer::after_millis(10).await;
+    }
+}
+
+#[embassy_executor::main]
+async fn main(spawner: Spawner) {
+    let p = embassy_imxrt::init(Default::default());
+
+    info!("UART test start");
+
+    let usart4 = Uart::new_blocking(p.FLEXCOMM4, p.PIO0_29, p.PIO0_30, Default::default()).unwrap();
+
+    let (_, usart4) = usart4.split();
+    spawner.must_spawn(usart4_task(usart4));
+
+    let usart2 = UartTx::new_blocking(p.FLEXCOMM2, p.PIO0_15, Default::default()).unwrap();
+    spawner.must_spawn(usart2_task(usart2));
+}