Fix async uart and add example for async uart echo

examples/ch32v307/src/bin/uart_echo_async.rs

@@ -0,0 +1,45 @@
+#![no_std]
+#![no_main]
+
+use embassy_executor::Spawner;
+use hal::gpio::{Level, Output};
+use hal::usart;
+use hal::usart::Uart;
+use {ch32_hal as hal, panic_halt as _};
+
+use ch32_hal::bind_interrupts;
+
+bind_interrupts!(struct Irqs {
+    USART4 => ch32_hal::usart::InterruptHandler<ch32_hal::peripherals::USART4>;
+});
+
+#[embassy_executor::main(entry = "ch32_hal::entry")]
+async fn main(_spawner: Spawner) -> ! {
+    let p = hal::init(Default::default());
+
+    // GPIO
+    let mut led = Output::new(p.PB4, Level::Low, Default::default());
+
+    let cfg = usart::Config::default();
+    let (mut tx_uart, mut rx_uart) = Uart::new(p.USART4, p.PE1, p.PE0, Irqs, p.DMA2_CH5, p.DMA2_CH3, cfg)
+        .unwrap()
+        .split();
+
+    tx_uart.write(b"Init ok\r\n").await.unwrap();
+
+    let mut buf = [0u8; 255];
+    loop {
+        match rx_uart.read_until_idle(&mut buf).await {
+            Ok(size) => {
+                for character in &mut buf[..size] {
+                    if *character >= b'a' && *character <= b'z' {
+                        *character -= 32;
+                    }
+                }
+                tx_uart.write(&buf[..size]).await.unwrap();
+                led.toggle();
+            }
+            Err(_err) => {}
+        }
+    }
+}

src/usart/mod.rs

@@ -838,6 +838,7 @@ impl<'d, T: Instance> Uart<'d, T, Async> {
 
         rx.set_as_input(Pull::None);
         tx.set_as_af_output(AFType::OutputPushPull, Speed::High);
+        T::set_remap(REMAP);
 
         Self::new_inner(
             peri,
@@ -869,6 +870,7 @@ impl<'d, T: Instance> Uart<'d, T, Async> {
         tx.set_as_af_output(AFType::OutputPushPull, Speed::High);
         rts.set_as_af_output(AFType::OutputPushPull, Speed::High);
         cts.set_as_input(Pull::None);
+        T::set_remap(REMAP);
 
         Self::new_inner(
             peri,