Low power UART driver

examples/src/bin/buffered_uart.rs

@@ -0,0 +1,84 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+#[path = "../example_common.rs"]
+mod example_common;
+use example_common::*;
+
+use cortex_m_rt::entry;
+use defmt::panic;
+use futures::pin_mut;
+use nrf52840_hal::gpio;
+
+use embassy::executor::{task, Executor};
+use embassy::io::{AsyncBufRead, AsyncBufReadExt, AsyncWrite, AsyncWriteExt};
+use embassy::util::Forever;
+use embassy_nrf::buffered_uarte;
+use embassy_nrf::interrupt;
+
+#[task]
+async fn run() {
+    let p = unwrap!(embassy_nrf::pac::Peripherals::take());
+
+    let port0 = gpio::p0::Parts::new(p.P0);
+
+    let pins = buffered_uarte::Pins {
+        rxd: port0.p0_08.into_floating_input().degrade(),
+        txd: port0
+            .p0_06
+            .into_push_pull_output(gpio::Level::Low)
+            .degrade(),
+        cts: None,
+        rts: None,
+    };
+
+    let irq = interrupt::take!(UARTE0_UART0);
+    let u = buffered_uarte::BufferedUarte::new(
+        p.UARTE0,
+        irq,
+        pins,
+        buffered_uarte::Parity::EXCLUDED,
+        buffered_uarte::Baudrate::BAUD115200,
+    );
+    pin_mut!(u);
+
+    info!("uarte initialized!");
+
+    unwrap!(u.write_all(b"Hello!\r\n").await);
+    info!("wrote hello in uart!");
+
+    // Simple demo, reading 8-char chunks and echoing them back reversed.
+    loop {
+        info!("reading...");
+        let mut buf = [0u8; 8];
+        unwrap!(u.read_exact(&mut buf).await);
+        info!("read done, got {:[u8]}", buf);
+
+        // Reverse buf
+        for i in 0..4 {
+            let tmp = buf[i];
+            buf[i] = buf[7 - i];
+            buf[7 - i] = tmp;
+        }
+
+        info!("writing...");
+        unwrap!(u.write_all(&buf).await);
+        info!("write done");
+    }
+}
+
+static EXECUTOR: Forever<Executor> = Forever::new();
+
+#[entry]
+fn main() -> ! {
+    info!("Hello World!");
+
+    let executor = EXECUTOR.put(Executor::new(cortex_m::asm::sev));
+    unwrap!(executor.spawn(run()));
+
+    loop {
+        executor.run();
+        cortex_m::asm::wfe();
+    }
+}

examples/src/bin/uart.rs

@@ -8,22 +8,76 @@ use example_common::*;
 
 use cortex_m_rt::entry;
 use defmt::panic;
-use futures::pin_mut;
+use embassy::executor::{task, Executor};
+use embassy::time::{Duration, Timer};
+use embassy::util::Forever;
+use embassy_nrf::{interrupt, pac, rtc, uarte};
+use futures::future::{select, Either};
+use nrf52840_hal::clocks;
 use nrf52840_hal::gpio;
 
-use embassy::executor::{task, Executor};
-use embassy::io::{AsyncBufRead, AsyncBufReadExt, AsyncWrite, AsyncWriteExt};
-use embassy::util::Forever;
-use embassy_nrf::buffered_uarte;
-use embassy_nrf::interrupt;
-
 #[task]
-async fn run() {
+async fn run(mut uart: uarte::Uarte<pac::UARTE0>) {
+    info!("uarte initialized!");
+
+    // Message must be in SRAM
+    let mut buf = [0; 8];
+    buf.copy_from_slice(b"Hello!\r\n");
+
+    uart.send(&buf).await;
+    info!("wrote hello in uart!");
+
+    info!("reading...");
+    loop {
+        let received = match select(
+            uart.receive(&mut buf),
+            Timer::after(Duration::from_millis(10)),
+        )
+        .await
+        {
+            Either::Left((buf, _)) => buf,
+            Either::Right((_, read)) => {
+                let (buf, n) = read.stop().await;
+                &buf[..n]
+            }
+        };
+
+        if received.len() > 0 {
+            info!("read done, got {:[u8]}", received);
+
+            // Echo back received data
+            uart.send(received).await;
+        }
+    }
+}
+
+static RTC: Forever<rtc::RTC<pac::RTC1>> = Forever::new();
+static ALARM: Forever<rtc::Alarm<pac::RTC1>> = Forever::new();
+static EXECUTOR: Forever<Executor> = Forever::new();
+
+#[entry]
+fn main() -> ! {
+    info!("Hello World!");
+
     let p = unwrap!(embassy_nrf::pac::Peripherals::take());
 
+    clocks::Clocks::new(p.CLOCK)
+        .enable_ext_hfosc()
+        .set_lfclk_src_external(clocks::LfOscConfiguration::NoExternalNoBypass)
+        .start_lfclk();
+
+    let rtc = RTC.put(rtc::RTC::new(p.RTC1, interrupt::take!(RTC1)));
+    rtc.start();
+
+    unsafe { embassy::time::set_clock(rtc) };
+
+    let alarm = ALARM.put(rtc.alarm0());
+    let executor = EXECUTOR.put(Executor::new_with_alarm(alarm, cortex_m::asm::sev));
+
+    // Init UART
     let port0 = gpio::p0::Parts::new(p.P0);
 
-    let pins = buffered_uarte::Pins {
+    let pins = uarte::Pins {
         rxd: port0.p0_08.into_floating_input().degrade(),
         txd: port0
             .p0_06
@@ -33,49 +87,18 @@ async fn run() {
         rts: None,
     };
 
-    let irq = interrupt::take!(UARTE0_UART0);
-    let u = buffered_uarte::BufferedUarte::new(
-        p.UARTE0,
-        irq,
-        pins,
-        buffered_uarte::Parity::EXCLUDED,
-        buffered_uarte::Baudrate::BAUD115200,
-    );
-    pin_mut!(u);
+    // NOTE(unsafe): Safe becasue we do not use `mem::forget` anywhere.
+    let uart = unsafe {
+        uarte::Uarte::new(
+            p.UARTE0,
+            interrupt::take!(UARTE0_UART0),
+            pins,
+            uarte::Parity::EXCLUDED,
+            uarte::Baudrate::BAUD115200,
+        )
+    };
 
-    info!("uarte initialized!");
-
-    unwrap!(u.write_all(b"Hello!\r\n").await);
-    info!("wrote hello in uart!");
-
-    // Simple demo, reading 8-char chunks and echoing them back reversed.
-    loop {
-        info!("reading...");
-        let mut buf = [0u8; 8];
-        unwrap!(u.read_exact(&mut buf).await);
-        info!("read done, got {:[u8]}", buf);
-
-        // Reverse buf
-        for i in 0..4 {
-            let tmp = buf[i];
-            buf[i] = buf[7 - i];
-            buf[7 - i] = tmp;
-        }
-
-        info!("writing...");
-        unwrap!(u.write_all(&buf).await);
-        info!("write done");
-    }
-}
-
-static EXECUTOR: Forever<Executor> = Forever::new();
-
-#[entry]
-fn main() -> ! {
-    info!("Hello World!");
-
-    let executor = EXECUTOR.put(Executor::new(cortex_m::asm::sev));
-    unwrap!(executor.spawn(run()));
+    unwrap!(executor.spawn(run(uart)));
 
     loop {
         executor.run();