STM32上Systick计时器的功耗

Question

In the code I'm working on ( STM32L4 project ) the Systick is enabled to tick every 1ms and its interrupt is enabled. This means every 1ms the CPU exits from WFI (currently the CPU spends around 2/3 of the time in Sleep mode). I am wondering if it does not consume too much power to use the Systick, what do you think ?

Answer 1

First, measure how long does the interrupt handler take. You can count the cycles with DWT->CYCCNT and some code (but it'll be quite inaccurate, not counting eg handler entry and exit cycles), or start a timer ( TIM2 or TIM5 as they are 32 bits, otherwise mind the overflow), tell the controller to stop it in sleep mode with the RCC->APBxSMENR register, then you'll have an exact count of cycles how long the controller was not sleeping.

When you know how long is the controller not sleeping, you can use STM32CubeMX to calculate power consumption.

Not using SysTick at all

If the only purpose of SysTick in your program is to maintain the milliseconds counter, you can use a 32 bit timer instead. Instead of starting Systick, start the timer, and replace references to the milliseconds counter with (TIM2->CNT) . When using HAL, it would be just

HAL_StatusTypeDef HAL_InitTick(uint32_t prio __attribute__((unused))) {
  RCC->APB1ENR = RCC_APB1ENR_TIM2EN;
  asm volatile("dsb sy");
  TIM2->CR1 = TIM_CR1_CEN;
  return HAL_OK;
}

uint32_t HAL_GetTick(void) {
  return TIM2->CNT;
}