本帖最后由 liuqian 于 2019-8-13 08:54 编辑

hal库中的源码
/**
  * @brief  Sets or clears the selected data port bit.
  *
  * @note   This function uses GPIOx_BSRR register to allow atomic read/modify
  *         accesses. In this way, there is no risk of an IRQ occurring between
  *         the read and the modify access.
  *
  * @param  GPIOx: where x can be (A..G depending on device used) to select the GPIO peripheral
  * @param  GPIO_Pin: specifies the port bit to be written.
  *          This parameter can be one of GPIO_PIN_x where x can be (0..15).
  * @param  PinState: specifies the value to be written to the selected bit.
  *          This parameter can be one of the GPIO_PinState enum values:
  *            @arg GPIO_PIN_RESET: to clear the port pin
  *            @arg GPIO_PIN_SET: to set the port pin
  * @retval None
  */
void HAL_GPIO_WritePin(GPIO_TypeDef *GPIOx, uint16_t GPIO_Pin, GPIO_PinState PinState)
{
  /* Check the parameters */
  assert_param(IS_GPIO_PIN(GPIO_Pin));
  assert_param(IS_GPIO_PIN_ACTION(PinState));

  if (PinState != GPIO_PIN_RESET)
  {
    GPIOx->BSRR = GPIO_Pin;
  }
  else
  {
    GPIOx->BSRR = (uint32_t)GPIO_Pin << 16U;                // 为什么不直接用GPIOx->BRR = GPIO_Pin，非要画蛇添足的去移位再写BSRR
  }
}

/**
  * @brief  Toggles the specified GPIO pin
  * @param  GPIOx: where x can be (A..G depending on device used) to select the GPIO peripheral
  * @param  GPIO_Pin: Specifies the pins to be toggled.
  * @retval None
  */
void HAL_GPIO_TogglePin(GPIO_TypeDef *GPIOx, uint16_t GPIO_Pin)
{
  /* Check the parameters */
  assert_param(IS_GPIO_PIN(GPIO_Pin));

  GPIOx->ODR ^= GPIO_Pin;                                // 不是原子操作了，有可能影响到其他的位，应该用BSRR和BRR才对呀
}