From 4b3e6d742a1a153d76e3f3d6ba8ad0dafd378e51 Mon Sep 17 00:00:00 2001
From: rubenasplund <ruben.asplund@hotmail.com>
Date: Fri, 4 Dec 2020 11:23:37 +0100
Subject: [PATCH] Exercise A
---
examples/rtt_timing.rs | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/examples/rtt_timing.rs b/examples/rtt_timing.rs
index 4ee6775..1dc033c 100644
--- a/examples/rtt_timing.rs
+++ b/examples/rtt_timing.rs
@@ -45,7 +45,7 @@ const APP: () = {
#[no_mangle]
fn timed_loop() -> (u32, u32) {
let start = DWT::get_cycle_count();
- for _ in 0..10000 {
+ for _ in 0..1000 {
asm::nop();
}
let end = DWT::get_cycle_count();
@@ -63,15 +63,15 @@ fn timed_loop() -> (u32, u32) {
// A.1) What is the cycle count for the loop?
// > cargo run --example rtt_timing
//
-// [Your answer here]
+// [The loop in timed_loop is looping 335424926-330634772 = 4790154 times]
//
// A.2) How many cycles per iteration?
//
-// [Your answer here]
+// [4790154/1000 = 4790]
//
// A.3) Why do we need a wrapping subtraction?
//
-// [Your answer here]
+// [Becasue the variable is a unsigned 32 bit int, which will overflow when taking substraction bit wise. Therefore a wrapper is there to make sure the substraction is correctly calculated even if it overflow.]
//
// ------------------------------------------------------------------------
// Now try a release (optimized build, see `Cargo.toml` for build options).
--
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