stm32: Fix watchdog division by zero for 256 prescaler, add watchdog example for H7

2 files changed, 28 insertions, 4 deletions

diff --git a/embassy-stm32/src/wdg/mod.rs b/embassy-stm32/src/wdg/mod.rs
index 85176eefc..92b9a5ca8 100644
--- a/embassy-stm32/src/wdg/mod.rs
+++ b/embassy-stm32/src/wdg/mod.rs
@@ -13,12 +13,12 @@ pub struct IndependentWatchdog<'d, T: Instance> {
 const MAX_RL: u16 = 0xFFF;
 
 /// Calculates maximum watchdog timeout in us (RL = 0xFFF) for a given prescaler
-const fn max_timeout(prescaler: u8) -> u32 {
+const fn max_timeout(prescaler: u16) -> u32 {
     1_000_000 * MAX_RL as u32 / (LSI_FREQ.0 / prescaler as u32)
 }
 
 /// Calculates watchdog reload value for the given prescaler and desired timeout
-const fn reload_value(prescaler: u8, timeout_us: u32) -> u16 {
+const fn reload_value(prescaler: u16, timeout_us: u32) -> u16 {
     (timeout_us / prescaler as u32 * LSI_FREQ.0 / 1_000_000) as u16
 }
 
@@ -33,12 +33,12 @@ impl<'d, T: Instance> IndependentWatchdog<'d, T> {
         // Find lowest prescaler value, which makes watchdog period longer or equal to timeout.
         // This iterates from 4 (2^2) to 256 (2^8).
         let psc_power = unwrap!((2..=8).find(|psc_power| {
-            let psc = 2u8.pow(*psc_power);
+            let psc = 2u16.pow(*psc_power);
             timeout_us <= max_timeout(psc)
         }));
 
         // Prescaler value
-        let psc = 2u8.pow(psc_power);
+        let psc = 2u16.pow(psc_power);
 
         // Convert prescaler power to PR register value
         let pr = psc_power as u8 - 2;
diff --git a/examples/stm32h7/src/bin/wdg.rs b/examples/stm32h7/src/bin/wdg.rs
new file mode 100644
index 000000000..2b0301aad
--- /dev/null
+++ b/examples/stm32h7/src/bin/wdg.rs
@@ -0,0 +1,24 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+
+use defmt::*;
+use embassy_executor::Spawner;
+use embassy_stm32::wdg::IndependentWatchdog;
+use embassy_time::{Duration, Timer};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let p = embassy_stm32::init(Default::default());
+    info!("Hello World!");
+
+    let mut wdg = IndependentWatchdog::new(p.IWDG1, 20_000_000);
+
+    unsafe { wdg.unleash() };
+
+    loop {
+        Timer::after(Duration::from_secs(1)).await;
+        unsafe { wdg.pet() };
+    }
+}