rtt_timing, E complete

.cargo/config

@@ -5,10 +5,10 @@
 [target.'cfg(all(target_arch = "arm", target_os = "none"))']
 # uncomment ONE of these three option to make `cargo run` start a GDB session
 # which option to pick depends on your system
-# runner = "arm-none-eabi-gdb -q -x openocd.gdb"
+runner = "arm-none-eabi-gdb -q -x openocd.gdb"
 # runner = "gdb-multiarch -q -x openocd.gdb"
 # runner = "gdb -q -x openocd.gdb"
-runner = "probe-run --chip STM32F411RETx"
+# runner = "probe-run --chip STM32F411RETx"
 
 rustflags = [
   # This is needed if your flash or ram addresses are not aligned to 0x10000 in memory.x

examples/rtt_timing.rs

@@ -260,11 +260,42 @@ A/C = 4790151/40001 = 119,7507812 ~= 120
 // https://developer.arm.com/documentation/ddi0439/b/Data-Watchpoint-and-Trace-Unit/DWT-Programmers-Model
 //
 // [Your answer here]
+/*
+The content of r1 is 0xE0001004. This is the address for the DWT_CYCCNT (Cycle count Register).
+There are no functions call in the loop function because the compiler has optimized the instructions to just reading from the
+cycle register and saving it in r0.
+*/
 //
 // Now check your answer by dumping the registers
 // (gdb) info registers
 //
 // [Register dump here]
+/*
+r0             0x80000000          -2147483648
+r1             0xe0001004          -536866812
+r2             0x2710              10000
+r3             0xa                 10
+r4             0x20000000          536870912
+r5             0x20000430          536871984
+r6             0x0                 0
+r7             0x2000ffe8          536936424
+r8             0x0                 0
+r9             0x0                 0
+r10            0x0                 0
+r11            0x0                 0
+r12            0x1                 1
+sp             0x2000ff98          0x2000ff98
+lr             0x8000373           134218611
+pc             0x800023e           0x800023e <rtt_timing::timed_loop+12>
+xPSR           0x81000000          -2130706432
+fpscr          0x0                 0
+msp            0x2000ff98          0x2000ff98
+psp            0x0                 0x0
+primask        0x1                 1
+basepri        0x0                 0
+faultmask      0x0                 0
+control        0x0                 0
+*/
 //
 // We can now set a breakpoint exactly at the `nop`.
 //
@@ -290,6 +321,9 @@ A/C = 4790151/40001 = 119,7507812 ~= 120
 // (gdb) x 0xe0001004
 //
 // [Your answer here]
+/*
+0xe0001004:     0xf73d58c8
+*/
 //
 // Now, let's execute one iteration:
 // (gdb) continue
@@ -297,10 +331,16 @@ A/C = 4790151/40001 = 119,7507812 ~= 120
 // What is now the current value of the cycle counter?
 //
 // [Your answer here]
+/*
+0xe0001004:     0xf73d58cc
+*/
 //
 // By how much does the cycle counter increase for each iteration?
 //
 // [Your answer here]
+/*
+It increases by 4.
+*/
 //
 // ------------------------------------------------------------------------
 // F) Reseting the cycle counter