Use window watchdog

controller/src/logic.rs

@@ -3,8 +3,8 @@ use crate::{
     tb6612fng::{Movement, Tb6612fng},
 };
 use core::sync::atomic::{AtomicU32, Ordering};
-use embassy_stm32::time::hz;
-use embassy_time::{Instant, Timer};
+use embassy_stm32::{pac::{self, wwdg::vals::Wdgtb}, peripherals::WWDG, time::hz};
+use embassy_time::{Duration, Instant, Ticker};
 use heapless::Deque;
 use i2c2_target::{I2C2, MESSAGE_SIZE};
 
@@ -94,19 +94,44 @@ fn current_millis() -> u32 {
     Instant::now().as_millis() as u32
 }
 
+fn wwdg_configure() {
+    // With PCLK1 at 36MHz, 63 as a timeout value with wdgtb at /8
+    // means 58.25ms.  Comparing with a value of 31 means that at
+    // least 29.125ms must have passed before the watchdog can be
+    // petted.
+    pac::WWDG.cfr().write(|w| {
+        w.set_wdgtb(Wdgtb::DIV8);
+        w.set_w((1 << 6) | 31);
+    });
+    wwdg_pet();
+}
+
+fn wwdg_pet() {
+    // Reset watchdog and start it if not started yet
+    pac::WWDG.cr().modify(|w| {
+        w.set_t((1 << 6) | 63);
+        w.set_wdga(true);
+    });
+}
+
+#[allow(clippy::used_underscore_binding)]  // Clippy bug
 #[embassy_executor::task]
 pub async fn start_i2c_target(
     i2c2: I2C2,
     mut motors: Tb6612fng<'static>,
     encoders: Encoders<'static>,
+    _wwdg: WWDG,
 ) {
     motors.standby_enter();
     unsafe {
         STATE = Some(State::new(i2c2, motors, encoders));
         STATE.as_mut().unwrap().i2c.start(&i2c_callback);
     }
+    wwdg_configure();
+    let mut ticker = Ticker::every(Duration::from_millis(50));
     loop {
-        Timer::after_millis(100).await;
+        ticker.next().await;
+        wwdg_pet();
         if current_millis() >= WATCHDOG_EXPIRATION.load(Ordering::Relaxed) {
             State::with_critical_section(|state| {
                 if state.is_moving()

controller/src/main.rs

@@ -34,7 +34,7 @@ async fn main(spawner: Spawner) {
         prediv: PllPreDiv::DIV1,
         mul: PllMul::MUL9,
     });
-    // APB1 speed is max 36MHz (SysClk/2)
+    // APB1 speed (PCLK1) is max 36MHz (SysClk/2), use that
     config.rcc.apb1_pre = APBPrescaler::DIV2;
     let p = embassy_stm32::init(config);
 
@@ -62,8 +62,9 @@ async fn main(spawner: Spawner) {
     let encoders = Encoders::new(p.PA0, p.PA1, p.PA6, p.PA7, p.TIM2, p.TIM3);
 
     let i2c2 = i2c2_target::I2C2::new(p.I2C2, p.PB10, p.PB11, 0x57, Priority::P3);
+
     spawner
-        .spawn(logic::start_i2c_target(i2c2, motors, encoders))
+        .spawn(logic::start_i2c_target(i2c2, motors, encoders, p.WWDG))
         .unwrap();
 }