Fixing system timer
@@ -74,7 +74,7 @@ impl rtic::Monotonic for SystemTimer {
// other task that is accessing the current time could potentially race for the
// registers. Note that this is only required for writing to global state (e.g. timer
// registers and overflow counter)
- cortex_m::interrupt::free(|_cs| {
+ if let Some(time) = cortex_m::interrupt::free(|_cs| {
// Check for overflows and clear the overflow bit atomically. This must be done in
// a critical section to prevent race conditions on the status register.
if regs.sr.read().uif().bit_is_set() {
@@ -89,9 +89,15 @@ impl rtic::Monotonic for SystemTimer {
// Check that an overflow didn't occur since we just cleared the overflow bit. If
// it did, loop around and retry.
if regs.sr.read().uif().bit_is_clear() {
- return (overflows * 65535 + current_value) as i32;
+ // Note(unsafe): We are in a critical section, so it is safe to read the
+ // global variable.
+ unsafe { Some((OVERFLOWS * 65535 + current_value) as i32) }
+ } else {
+ None
+ }
+ }) {
+ return time;
}
- })
}
}
