Merge pull request #254 from TheZoq2/fix_mono_timer

Fix mono timer

Author: therealprof

src/time.rs

@@ -28,7 +28,7 @@
 //! ```
 
 use core::ops;
-use cortex_m::peripheral::DWT;
+use cortex_m::peripheral::{DCB, DWT};
 
 use crate::rcc::Clocks;
 
@@ -227,14 +227,20 @@ impl_arithmetic!(MegaHertz, u32);
 impl_arithmetic!(Bps, u32);
 
 /// A monotonic non-decreasing timer
+///
+/// This uses the timer in the debug watch trace peripheral. This means, that if the
+/// core is stopped, the timer does not count up. This may be relevant if you are using
+/// cortex_m_semihosting::hprintln for debugging in which case the timer will be stopped
+/// while printing
 #[derive(Clone, Copy)]
 pub struct MonoTimer {
     frequency: Hertz,
 }
 
 impl MonoTimer {
     /// Creates a new `Monotonic` timer
-    pub fn new(mut dwt: DWT, clocks: Clocks) -> Self {
+    pub fn new(mut dwt: DWT, mut dcb: DCB, clocks: Clocks) -> Self {
+        dcb.enable_trace();
         dwt.enable_cycle_counter();
 
         // now the CYCCNT counter can't be stopped or reset