Exercise F

examples/rtt_timing.rs

 //! examples/rtt_timing.rs
 
-#![deny(unsafe_code)]
+//#![deny(unsafe_code)]
 #![deny(warnings)]
 #![no_main]
 #![no_std]
 
 use cortex_m::{asm, peripheral::DWT};
-use panic_rtt_target as _;
-use rtt_target::{rprintln, rtt_init_print};
+use panic_halt as _;
+//use panic_rtt_target as _;
+//use rtt_target::{rprintln, rtt_init_print};
 use stm32f4;
 
 #[rtic::app(device = stm32f4)]
 const APP: () = {
     #[init]
     fn init(mut cx: init::Context) {
-        rtt_init_print!();
-        rprintln!("init");
+        //rtt_init_print!();
+        //rprintln!("init");
 
         // Initialize (enable) the monotonic timer (CYCCNT)
         cx.core.DCB.enable_trace();
         cx.core.DWT.enable_cycle_counter();
 
-        rprintln!("start timed_loop");
-        let (start, end) = timed_loop();
-        rprintln!(
-            "start {}, end {}, diff {}",
-            start,
-            end,
-            end.wrapping_sub(start)
-        );
+        //rprintln!("start timed_loop");
+        //unsafe {
+        //    cx.core.DWT.cyccnt.write(0);
+        //}
+        
+        let (_start, _end) = timed_loop();
+        // rprintln!(
+        //     "start {}, end {}, diff {}",
+        //     start,
+        //     end,
+        //     end.wrapping_sub(start)
+        // );
     }
 
     #[idle]
     fn idle(_cx: idle::Context) -> ! {
-        rprintln!("idle");
+        // rprintln!("idle");
         loop {
             continue;
         }
@@ -299,7 +304,7 @@ fn timed_loop() -> (u32, u32) {
 // What is the initial value of the cycle counter
 // (when hitting the `timed_loop` breakpoint)?
 //
-// [Your answer here]
+// [0x00000006]
 //
 // ------------------------------------------------------------------------
 // F) Finally some statics
@@ -340,6 +345,10 @@ fn timed_loop() -> (u32, u32) {
 // > cargo size --example rtt_timing --release --features nightly
 //
 // [Your answer here]
+// Compiling app v0.1.0 (/home/ruben/git/rtic_f4xx_nucleo)
+// Finished release [optimized + debuginfo] target(s) in 0.44s
+// text    data     bss     dec     hex filename
+// 660       0       0     660     294 rtt_timing
 //
 // I was able to get down to:
 // > cargo size --example rtt_timing --release --features nightly