serj-bashlayev/stm32_profiler

Simple and fast code profiler for STM32 ARM Cortex-M CPU family

Code profiling for STM32

Features

Simple and fast code profiler for STM32 ARM Cortex-M CPU family.
Allow measuring time intervals and printing it in table view to SWO debug port.
Use Data Watchpoint and Trace (DWT) cycle counter (DWT_CYCCNT).

Example data print

Profiling "Start" sequence:                                
--Event-----------------------|--timestamp--|---delta_t----
GLCD_Init                     :       41 us | +       41 us
OLED_Init                     :     5288 us | +     5247 us
u8g_SetFont                   :     5292 us | +        4 us
HAL_Delay(10)                 : 10004967 us | +  9999675 us

Minimum measure time = 0 µs
Maximum measure time = 59,6 sec at core clock 72 MHz
Time accuracy ±1 µs.

Easy to use. Easy to port to another ARM architecture and programming language.

Technical background:
SWO is a dedicated pin of ARM's Cortex-M debug interface. While it can be used to output various information in real time by the CPU, it's main usage is terminal I/O in real time with very low intrusion. Most programs can perform debug outputs without losing their real time behavior.
Cycle Count Register (DWT_CYCCNT): 32-bit, incrementing (up) cycle counter. When enabled, this counter counts the number of core cycles. Counting is suspended when the core is halted in Debug state. CYCCNT wraps to 0 on overflow.

How to use

start profiling session
PROFILING_START("*session name*");

Insert timestamp command as many times as necessary.^[1]
PROFILING_EVENT("*event name*");

close profiling session and read it times on Serial wire viewer (SWV)
PROFILING_STOP();

Example code

int main(void)
{
  SysTick_Config(SystemCoreClock / 1000);
  
  PROFILING_START("MAIN startup timing");

  Init_IO();
  PROFILING_EVENT("IO_Init()");

  Init_TIM6();
  PROFILING_EVENT("TIM6_Init()");

  PROFILING_STOP();

  while (1)
  {
    PROFILING_START("MAIN loop timing");

    GPIO_WriteBit(GPIOE, GPIO_Pin_9, (((Tick % 1000) > 500) ? Bit_SET : Bit_RESET));
    PROFILING_EVENT("GPIO_WriteBit(...)");

    // Wait for update Tick
    delay_tick = Tick;
    while (delay_tick == Tick);
    PROFILING_EVENT("Wait for update Tick");

    // Delay 1000 ms
    delay_tick = Tick + 1000;
    while (delay_tick > Tick);
    PROFILING_EVENT("DELAY 1 s");

    // Stop profiling and print
    PROFILING_STOP();
  }
}

Debug (printf) Viewer example

Profiling "MAIN startup timing" sequence: 
--Event-----------------------|--timestamp--|----delta_t---
IO_Init()                     :        9 µs | +        9 µs
TIM6_Init()                   :       18 µs | +        8 µs

Profiling "MAIN loop timing" sequence: 
--Event-----------------------|--timestamp--|----delta_t---
GPIO_WriteBit(...)            :        1 µs | +        1 µs
Wait for update Tick          :      797 µs | +      795 µs
DELAY 1 s                     :  1000797 µs | +   999999 µs

For more information, how to use the Keil µVision Debug (printf) Viewer see http://www.keil.com/support/man/docs/ulink2/ulink2_trace_itm_viewer.htm
You can also use ST-LINK - Printf via SWO viewer feature or other debugging software with SWO Viewer support.

---

note 1 The maximum number of events is defined in MAX_EVENT_COUNT (profiling.h)

stm32_profiler's Issues

"DWT->LAR" not recognized when compiling for STM32F103

The compiler shows error in the function

void PROFILING_START(const char *profile_name)
{
  prof_name = profile_name;
  event_count = 0;

  CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
  DWT->LAR = 0xC5ACCE55; // <<<<<<<< 'DWT_Type {aka struct <anonymous>}' has no member named 'LAR'
  DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk; // enable counter
  //DWT->CYCCNT  = time_start = 0;
  time_start = DWT->CYCCNT;
}

Looking at the core headers, "LAR" field is in "ITM_Type" struct, not in "DWT_Type".
The issue occurs within Platformio IDE using stm32cube framework.