1、进入睡眠的关键语句

RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR, ENABLE);

PWR_EnterSTOPMode(PWR_Regulator_LowPower, PWR_STOPEntry_WFI);

2、进入低功耗需要的配置，GPIO配置原则：不回路，不悬空输入。下面是将所有IO输出为0

//输出
GPIOA->MODER = 0x55555555;
GPIOB->MODER = 0x55555555;
GPIOC->MODER = 0x55555555;
GPIOD->MODER = 0x55555555;
GPIOF->MODER = 0x55555555;
//即不上拉，也不下拉
GPIOA->PUPDR = 0x00000000;
GPIOB->PUPDR = 0x00000000;
GPIOC->PUPDR = 0x00000000;
GPIOD->PUPDR = 0x00000000;
GPIOF->PUPDR = 0x00000000;
//输出0
GPIOA->ODR=0x00000000;
GPIOB->ODR=0x00000000;
GPIOC->ODR=0x00000000;
GPIOD->ODR=0x00000000;
GPIOF->ODR=0x00000000;

3、非常重要：在配置IO之前，一定要先开启GPIO时钟

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA, ENABLE);
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOB, ENABLE);
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOC, ENABLE);
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOD, ENABLE);
RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOF, ENABLE);