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【带LED灯提示的程序】
#include <stdio.h>
#include <stm32l476xx.h>
// 供printf使用, 项目属性中勾选Use MicroLIB后有效
int fputc(int ch, FILE *fp)
{
if (fp == &__stdout)
{
if (ch == '\n')
{
// 自动添加\r
while ((USART2->ISR & USART_ISR_TXE) == 0); // 等待TDR可写入
USART2->TDR = '\r';
}
while ((USART2->ISR & USART_ISR_TXE) == 0);
USART2->TDR = ch;
}
return ch;
}
int main(void)
{
RCC->AHB2ENR = RCC_AHB2ENR_GPIOAEN; // 开PA时钟
RCC->APB1ENR1 = RCC_APB1ENR1_LPTIM1EN | RCC_APB1ENR1_PWREN | RCC_APB1ENR1_USART2EN; // 开低功耗定时器1和串口2时钟
RCC->CSR |= RCC_CSR_LSION; // 开LSI
while ((RCC->CSR & RCC_CSR_LSIRDY) == 0); // 等待LSI稳定
RCC->CCIPR = RCC_CCIPR_LPTIM1SEL_0; // LPTIM1时钟选LSI
GPIOA->MODER &= ~(GPIO_MODER_MODE2_0 | GPIO_MODER_MODE3_0); // 串口2端口: PA2~3设为复用模式
GPIOA->MODER &= ~GPIO_MODER_MODE5_1; // LED灯: PA5设为普通输出(推挽输出)
GPIOA->BSRR = GPIO_BSRR_BS5; // 开LED灯
// 根据芯片手册的Table 16. Alternate function AF0 to AF7可知
// PA2-3的复用功能应映射为AF7才是USART2的功能
GPIOA->AFR[0] = GPIO_AFRL_AFSEL2_2 | GPIO_AFRL_AFSEL2_1 | GPIO_AFRL_AFSEL2_0;
GPIOA->AFR[0] |= GPIO_AFRL_AFSEL3_2 | GPIO_AFRL_AFSEL3_1 | GPIO_AFRL_AFSEL3_0;
USART2->BRR = 417; // 波特率: 9600
USART2->CR1 = USART_CR1_UE | USART_CR1_TE | USART_CR1_RE | USART_CR1_RXNEIE; // 打开串口2, 允许收发, 开接收中断
NVIC_EnableIRQ(USART2_IRQn); // 允许执行串口中断函数
LPTIM1->CFGR = LPTIM_CFGR_PRESC_1; // 4分频
LPTIM1->IER = LPTIM_IER_ARRMIE; // 开定时器中断
NVIC_EnableIRQ(LPTIM1_IRQn); // 允许执行定时器中断函数
LPTIM1->CR = LPTIM_CR_ENABLE; // 打开LPTIM, 但暂不开始计时
LPTIM1->ARR = 39999; // 计时5s
printf("Press 1 to enter stop mode: \n");
while (1);
}
// 低功耗定时器中断
void LPTIM1_IRQHandler(void)
{
if (LPTIM1->ISR & LPTIM_ISR_ARRM)
{
LPTIM1->ICR = LPTIM_ICR_ARRMCF;
SCB->SCR &= ~SCB_SCR_SLEEPONEXIT_Msk; // 退出中断时不再自动进入低功耗模式
USART2->CR1 |= USART_CR1_UE; // 开串口
GPIOA->BSRR = GPIO_BSRR_BS5; // PA5=1, 开LED灯
printf("Waked up!\n");
}
}
// 串口2中断
void USART2_IRQHandler(void)
{
uint8_t ch;
if (USART2->ISR & USART_ISR_RXNE)
{
ch = USART2->RDR; // 读取接收到的数据
if (ch == '1')
{
// 串口发送1进入睡眠模式
printf("Enter stop mode!\n");
while ((USART2->ISR & USART_ISR_TC) == 0); // 等待串口数据收发完毕
USART2->CR1 &= ~USART_CR1_UE; // 关闭串口
LPTIM1->CR |= LPTIM_CR_SNGSTRT; // 定时器开始计时
GPIOA->BRR = GPIO_BRR_BR5; // PA5=0, 关LED灯
PWR->CR1 |= PWR_CR1_LPMS_STOP2;
SCB->SCR |= SCB_SCR_SLEEPDEEP_Msk | SCB_SCR_SLEEPONEXIT_Msk; // 离开中断时自动进入Stop 2模式
}
}
}
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