Merge pull request #862 from mrwatts88/serial-irq-example

Serial IRQ example

Author: burrbull

Cargo.toml

@@ -724,6 +724,10 @@ required-features = ["gpiod", "sdio", "sdio-host"] # stm32f405
 name = "serial"
 required-features = []
 
+[[example]]
+name = "serial-echo-irq"
+required-features = []
+
 [[example]]
 name = "serial-9bit"
 required-features = ["gpiod"] # stm32f411

examples/serial-echo-irq.rs

@@ -0,0 +1,88 @@
+//! Serial echo using USART RX interrupt
+//!
+//! This example demonstrates interrupt-driven serial reception with echo.
+//! Characters received on USART2 are echoed back.
+//!
+//! Tested on STM32F446 Nucleo board where USART2 is connected to the
+//! ST-LINK virtual COM port (PA2=TX, PA3=RX).
+//!
+//! ```bash
+//! cargo run --features stm32f446 --release --example serial-echo-irq
+//! ```
+//!
+//! Example connection with picocom:
+//!
+//! ```bash
+//! picocom -b 115200 /dev/ttyACM0
+//! ```
+//!
+//! Type into the picocom terminal to see characters echoed.
+//! You will also see the characters logged in the terminal connected to the board.
+//!
+
+#![no_std]
+#![no_main]
+
+use core::cell::RefCell;
+use cortex_m::interrupt::Mutex;
+use cortex_m_rt::entry;
+use panic_halt as _;
+use rtt_target::{rprintln, rtt_init_print};
+
+use stm32f4xx_hal::{
+    interrupt, pac,
+    prelude::*,
+    rcc::Config,
+    serial::{self, Serial},
+};
+
+type SerialType = Serial<pac::USART2>;
+static SERIAL: Mutex<RefCell<Option<SerialType>>> = Mutex::new(RefCell::new(None));
+
+#[entry]
+fn main() -> ! {
+    rtt_init_print!();
+
+    let dp = pac::Peripherals::take().unwrap();
+    let mut rcc = dp.RCC.freeze(Config::hsi().sysclk(48.MHz()));
+    let gpioa = dp.GPIOA.split(&mut rcc);
+
+    let tx = gpioa.pa2;
+    let rx = gpioa.pa3;
+
+    let mut serial: SerialType = Serial::new(
+        dp.USART2,
+        (tx, rx),
+        serial::Config::default().baudrate(115200.bps()),
+        &mut rcc,
+    )
+    .unwrap();
+
+    serial.listen(serial::Event::RxNotEmpty);
+
+    cortex_m::interrupt::free(|cs| {
+        SERIAL.borrow(cs).replace(Some(serial));
+    });
+
+    // Enable USART2 interrupt
+    unsafe {
+        pac::NVIC::unmask(pac::Interrupt::USART2);
+    }
+
+    #[allow(clippy::empty_loop)]
+    loop {}
+}
+
+#[interrupt]
+fn USART2() {
+    cortex_m::interrupt::free(|cs| {
+        if let Some(serial) = SERIAL.borrow(cs).borrow_mut().as_mut() {
+            if let Ok(byte) = serial.read() {
+                rprintln!("Received: {} ('{}')", byte, byte as char);
+
+                // Echo received byte
+                let _ = serial.write(byte);
+            }
+        }
+    });
+}