stm32/usart: add baudrate calc test.

tests/stm32/Cargo.toml

@@ -3,6 +3,7 @@ edition = "2021"
 name = "embassy-stm32-tests"
 version = "0.1.0"
 license = "MIT OR Apache-2.0"
+autobins = false
 
 [features]
 stm32f103c8 = ["embassy-stm32/stm32f103c8", "not-gpdma"]     # Blue Pill

tests/stm32/build.rs

@@ -6,15 +6,16 @@ fn main() -> Result<(), Box<dyn Error>> {
     let out = PathBuf::from(env::var("OUT_DIR").unwrap());
     fs::write(out.join("link_ram.x"), include_bytes!("link_ram.x")).unwrap();
     println!("cargo:rustc-link-search={}", out.display());
-    println!("cargo:rerun-if-changed=link_ram.x");
-
     println!("cargo:rustc-link-arg-bins=--nmagic");
 
     // too little RAM to run from RAM.
-    #[cfg(any(feature = "stm32c031c6"))]
+    if cfg!(any(feature = "stm32c031c6")) {
         println!("cargo:rustc-link-arg-bins=-Tlink.x");
-    #[cfg(not(any(feature = "stm32c031c6")))]
+        println!("cargo:rerun-if-changed=link.x");
+    } else {
         println!("cargo:rustc-link-arg-bins=-Tlink_ram.x");
+        println!("cargo:rerun-if-changed=link_ram.x");
+    }
 
     println!("cargo:rustc-link-arg-bins=-Tdefmt.x");
 

tests/stm32/src/bin/usart.rs

@@ -9,6 +9,7 @@ use embassy_executor::Spawner;
 use embassy_stm32::dma::NoDma;
 use embassy_stm32::interrupt;
 use embassy_stm32::usart::{Config, Uart};
+use embassy_time::{Duration, Instant};
 use example_common::*;
 
 #[embassy_executor::main]
@@ -19,26 +20,27 @@ async fn main(_spawner: Spawner) {
     // Arduino pins D0 and D1
     // They're connected together with a 1K resistor.
     #[cfg(feature = "stm32f103c8")]
-    let (tx, rx, usart, irq) = (p.PA9, p.PA10, p.USART1, interrupt::take!(USART1));
+    let (mut tx, mut rx, mut usart, mut irq) = (p.PA9, p.PA10, p.USART1, interrupt::take!(USART1));
     #[cfg(feature = "stm32g491re")]
-    let (tx, rx, usart, irq) = (p.PC4, p.PC5, p.USART1, interrupt::take!(USART1));
+    let (mut tx, mut rx, mut usart, mut irq) = (p.PC4, p.PC5, p.USART1, interrupt::take!(USART1));
     #[cfg(feature = "stm32g071rb")]
-    let (tx, rx, usart, irq) = (p.PC4, p.PC5, p.USART1, interrupt::take!(USART1));
+    let (mut tx, mut rx, mut usart, mut irq) = (p.PC4, p.PC5, p.USART1, interrupt::take!(USART1));
     #[cfg(feature = "stm32f429zi")]
-    let (tx, rx, usart, irq) = (p.PG14, p.PG9, p.USART6, interrupt::take!(USART6));
+    let (mut tx, mut rx, mut usart, mut irq) = (p.PG14, p.PG9, p.USART6, interrupt::take!(USART6));
     #[cfg(feature = "stm32wb55rg")]
-    let (tx, rx, usart, irq) = (p.PA2, p.PA3, p.LPUART1, interrupt::take!(LPUART1));
+    let (mut tx, mut rx, mut usart, mut irq) = (p.PA2, p.PA3, p.LPUART1, interrupt::take!(LPUART1));
     #[cfg(feature = "stm32h755zi")]
-    let (tx, rx, usart, irq) = (p.PB6, p.PB7, p.USART1, interrupt::take!(USART1));
+    let (mut tx, mut rx, mut usart, mut irq) = (p.PB6, p.PB7, p.USART1, interrupt::take!(USART1));
     #[cfg(feature = "stm32u585ai")]
-    let (tx, rx, usart, irq) = (p.PD8, p.PD9, p.USART3, interrupt::take!(USART3));
+    let (mut tx, mut rx, mut usart, mut irq) = (p.PD8, p.PD9, p.USART3, interrupt::take!(USART3));
     #[cfg(feature = "stm32h563zi")]
-    let (tx, rx, usart, irq) = (p.PB6, p.PB7, p.LPUART1, interrupt::take!(LPUART1));
+    let (mut tx, mut rx, mut usart, mut irq) = (p.PB6, p.PB7, p.LPUART1, interrupt::take!(LPUART1));
     #[cfg(feature = "stm32c031c6")]
-    let (tx, rx, usart, irq) = (p.PB6, p.PB7, p.USART1, interrupt::take!(USART1));
+    let (mut tx, mut rx, mut usart, mut irq) = (p.PB6, p.PB7, p.USART1, interrupt::take!(USART1));
 
+    {
         let config = Config::default();
-    let mut usart = Uart::new(usart, rx, tx, irq, NoDma, NoDma, config);
+        let mut usart = Uart::new(&mut usart, &mut rx, &mut tx, &mut irq, NoDma, NoDma, config);
 
         // We can't send too many bytes, they have to fit in the FIFO.
         // This is because we aren't sending+receiving at the same time.
@@ -49,6 +51,45 @@ async fn main(_spawner: Spawner) {
         let mut buf = [0; 2];
         usart.blocking_read(&mut buf).unwrap();
         assert_eq!(buf, data);
+    }
+
+    // Test that baudrate divider is calculated correctly.
+    // Do it by comparing the time it takes to send a known number of bytes.
+    for baudrate in [
+        300,
+        9600,
+        115200,
+        250_000,
+        337_934,
+        #[cfg(not(feature = "stm32f103c8"))]
+        1_000_000,
+        #[cfg(not(feature = "stm32f103c8"))]
+        2_000_000,
+    ] {
+        info!("testing baudrate {}", baudrate);
+
+        let mut config = Config::default();
+        config.baudrate = baudrate;
+        let mut usart = Uart::new(&mut usart, &mut rx, &mut tx, &mut irq, NoDma, NoDma, config);
+
+        let n = (baudrate as usize / 100).max(64);
+
+        let start = Instant::now();
+        for _ in 0..n {
+            usart.blocking_write(&[0x00]).unwrap();
+        }
+        let dur = Instant::now() - start;
+        let want_dur = Duration::from_micros(n as u64 * 10 * 1_000_000 / (baudrate as u64));
+        let fuzz = want_dur / 5;
+        if dur < want_dur - fuzz || dur > want_dur + fuzz {
+            defmt::panic!(
+                "bad duration for baudrate {}: got {:?} want {:?}",
+                baudrate,
+                dur,
+                want_dur
+            );
+        }
+    }
 
     info!("Test OK");
     cortex_m::asm::bkpt();

tests/stm32/src/example_common.rs

@@ -16,5 +16,10 @@ pub fn config() -> Config {
         config.rcc.pll1.q_ck = Some(Hertz(100_000_000));
     }
 
+    #[cfg(feature = "stm32u585ai")]
+    {
+        config.rcc.mux = embassy_stm32::rcc::ClockSrc::MSI(embassy_stm32::rcc::MSIRange::Range48mhz);
+    }
+
     config
 }