rp2040: add {tx,rx}-only constructors to UART

examples/rp/src/bin/uart_unidir.rs

@@ -0,0 +1,42 @@
+//! test TX-only and RX-only UARTs. You need to connect GPIO0 to GPIO5 for
+//! this to work
+
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_rp::peripherals::UART1;
+use embassy_rp::uart::{Async, Config, UartRx, UartTx};
+use embassy_time::{Duration, Timer};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(spawner: Spawner) {
+    let p = embassy_rp::init(Default::default());
+
+    let mut uart_tx = UartTx::new(p.UART0, p.PIN_0, p.DMA_CH0, Config::default());
+    let uart_rx = UartRx::new(p.UART1, p.PIN_5, p.DMA_CH1, Config::default());
+
+    unwrap!(spawner.spawn(reader(uart_rx)));
+
+    info!("Writing...");
+    loop {
+        let data = [1u8, 2, 3, 4, 5, 6, 7, 8];
+        info!("TX {:?}", data);
+        uart_tx.write(&data).await.unwrap();
+        Timer::after(Duration::from_secs(1)).await;
+    }
+}
+
+#[embassy_executor::task]
+async fn reader(mut rx: UartRx<'static, UART1, Async>) {
+    info!("Reading...");
+    loop {
+        // read a total of 4 transmissions (32 / 8) and then print the result
+        let mut buf = [0; 32];
+        rx.read(&mut buf).await.unwrap();
+        info!("RX {:?}", buf);
+    }
+}