Cortex-M Cycle Counter counter

counter.c

uint32_t cycles;

cycles = 0;
CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
#ifdef STM32F7
DWT->LAR = 0xC5ACCE55;
#endif
DWT->CYCCNT = 0;
DWT->CTRL |=  DWT_CTRL_CYCCNTENA_Msk;
  
/* Process ... */

DWT->CTRL &= !DWT_CTRL_CYCCNTENA_Msk;
cycles = DWT->CYCCNT;

float seconds = (float) cycles / HAL_RCC_GetSysClockFreq();
// float seconds = (float) cycles / SystemCoreClock;
printf("%d cycles ", (int) cycles);
printf("(%0.4f ms @ %0.1f MHz).\n", (float) seconds * 1000.0f, SystemCoreClock / 1e6f);