STM32 Low-Power Modes: Sleep, Stop and Standby with HAL Examples

/* USER CODE BEGIN Includes */
#include <stdio.h>
/* USER CODE END Includes */

/* USER CODE BEGIN 0 */
int _write(int file, char *ptr, int len)
{
  (void)file;
  HAL_UART_Transmit(&huart2, (uint8_t *)ptr, (uint16_t)len, HAL_MAX_DELAY);
  return len;
}

static void blink(uint32_t times)
{
  for (uint32_t i = 0; i < times * 2U; i++)
  {
    HAL_GPIO_TogglePin(LD2_GPIO_Port, LD2_Pin);
    HAL_Delay(150);
  }
  HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_RESET);
}

/* B1 interrupt: only needed to wake the CPU, nothing else to do */
void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin)
{
  (void)GPIO_Pin;
}
/* USER CODE END 0 */

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_USART2_UART_Init();

  /* USER CODE BEGIN 2 */
  /* Did we just come out of Standby? SB flag survives the wake-up reset */
  if (__HAL_PWR_GET_FLAG(PWR_FLAG_SB) != RESET)
  {
    __HAL_PWR_CLEAR_FLAG(PWR_FLAG_SB);
    printf("\r\nWoke up from STANDBY (program restarted)\r\n");
  }
  else
  {
    printf("\r\nNormal power-on or reset\r\n");
  }
  /* USER CODE END 2 */

  while (1)
  {
    /* USER CODE BEGIN 3 */
    /* ---------- 1. SLEEP: CPU stops, peripherals keep running ---------- */
    blink(3);
    printf("Entering SLEEP, press B1 to wake\r\n");
    HAL_SuspendTick();   /* otherwise the 1 ms SysTick wakes us at once */
    HAL_PWR_EnterSLEEPMode(PWR_MAINREGULATOR_ON, PWR_SLEEPENTRY_WFI);
    HAL_ResumeTick();
    printf("Woke from SLEEP\r\n");

    /* ---------- 2. STOP: clocks off, RAM kept, wake by EXTI ---------- */
    blink(3);
    printf("Entering STOP, press B1 to wake\r\n");
    HAL_SuspendTick();
    HAL_PWR_EnterSTOPMode(PWR_LOWPOWERREGULATOR_ON, PWR_STOPENTRY_WFI);
    /* Execution resumes here on HSI 16 MHz: rebuild the 84 MHz clock */
    SystemClock_Config();
    HAL_ResumeTick();
    printf("Woke from STOP, clock restored to %lu Hz\r\n", SystemCoreClock);

    /* ---------- 3. STANDBY: lowest power, wake = reset ---------- */
    blink(3);
    printf("Entering STANDBY, touch PA0 to 3V3 to wake\r\n");
    HAL_Delay(20);                          /* let the UART finish */
    HAL_PWR_DisableWakeUpPin(PWR_WAKEUP_PIN1);
    __HAL_PWR_CLEAR_FLAG(PWR_FLAG_WU);      /* clear any old wake-up flag */
    HAL_PWR_EnableWakeUpPin(PWR_WAKEUP_PIN1);
    HAL_PWR_EnterSTANDBYMode();
    /* Never reached: wake-up from Standby restarts at main() */
    /* USER CODE END 3 */
  }
}