profiler.h File Reference

DWT-based microsecond profiler for ARM Cortex-M microcontrollers. More...

#include "main.h"

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Data Structures
struct	ProfileResult

Macros
#define	ENABLE_PROFILING
#define	PROFILER_START(p_result)   (p_result)->start_time = DWT->CYCCNT
#define	PROFILER_STOP(p_result)

Functions
void	initDWT (void)
	Initializes the DWT (Data Watchpoint and Trace) cycle counter.

Detailed Description

DWT-based microsecond profiler for ARM Cortex-M microcontrollers.

Author

Francesco Abate

Date

2025-09-25

This header provides a set of macros to easily measure the execution time of code blocks with high precision using the DWT cycle counter.

— HOW TO USE —

1. Initialize the counter once at the beginning of your main() function by calling:

   PROFILER_INIT();

2. In the function where you want to measure code, declare a ProfileResult variable:

   ProfileResult my_measurement;

3. Wrap the code you want to measure with the PROFILER_START and PROFILER_STOP macros:

   PROFILER_START(&my_measurement);
    
   // ... your code to be timed goes here ...
    
   PROFILER_STOP(&my_measurement);

4. Access the results from the my_measurement variable. The results are available in cycles, nanoseconds, microseconds, and milliseconds.

   printf("Task took: %.3f ms\n", my_measurement.elapsed_ms);
   printf("Cycles: %lu, Time: %.3f us\n", my_measurement.elapsed_cycles, my_measurement.elapsed_us);

5. To disable profiling for a release build, simply comment out the #define ENABLE_PROFILING line below. All profiling macros will compile to nothing, adding zero overhead.

Definition in file profiler.h.

Macro Definition Documentation

ENABLE_PROFILING

#define ENABLE_PROFILING

Definition at line 50 of file profiler.h.

PROFILER_START

#define PROFILER_START

(

p_result

)

(p_result)->start_time = DWT->CYCCNT

Definition at line 94 of file profiler.h.

PROFILER_STOP

#define PROFILER_STOP

(

p_result

)

Value:

        do { \
            (p_result)->elapsed_cycles = DWT->CYCCNT - (p_result)->start_time; \
            float clock_period_ns = 1000000000.0f / SystemCoreClock; \
            (p_result)->elapsed_ns = (float)(p_result)->elapsed_cycles * clock_period_ns; \
            (p_result)->elapsed_us = (p_result)->elapsed_ns / 1000.0f; \
            (p_result)->elapsed_ms = (p_result)->elapsed_us / 1000.0f; \
        } while(0)

Definition at line 97 of file profiler.h.

Function Documentation

initDWT()

void initDWT

(

void

)

Initializes the DWT (Data Watchpoint and Trace) cycle counter.

This function enables the high-precision cycle counter available on ARM Cortex-M processors (M3, M4, M7, etc.). It is used for creating very short, accurate delays or for performance profiling. The counter increments on every CPU clock cycle.

It performs the following steps:

1. Enables the Trace module via the CoreDebug peripheral.
2. Resets the cycle counter to zero.
3. Enables the cycle counter.

Note

This function must be called once at startup before any functions that rely on the DWT counter (e.g., DWT_Delay_us()).

Definition at line 70 of file profiler.h.

                  {
    CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk; // Enable trace
    DWT->CYCCNT = 0; // Reset the counter
    DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk; // Enable cycle counter
}

Referenced by main().

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