5. 串口

#include "stm32f10x.h"
#include <stdio.h>

// USART1 初始化：115200bps
void USART1_Config(void)
{
    GPIO_InitTypeDef GPIO_InitStructure;
    USART_InitTypeDef USART_InitStructure;

    // 使能时钟
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 |
                           RCC_APB2Periph_GPIOA, ENABLE);

    // TX(PA9) 复用推挽输出
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    // RX(PA10) 浮空输入
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(GPIOA, &GPIO_InitStructure);

    // USART1 配置
    USART_InitStructure.USART_BaudRate = 115200;
    USART_InitStructure.USART_WordLength = USART_WordLength_8b;
    USART_InitStructure.USART_StopBits = USART_StopBits_1;
    USART_InitStructure.USART_Parity = USART_Parity_No;
    USART_InitStructure.USART_HardwareFlowControl =
        USART_HardwareFlowControl_None;
    USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
    USART_Init(USART1, &USART_InitStructure);

    USART_Cmd(USART1, ENABLE);
}

// 发送一个字节
void USART1_SendByte(uint8_t data)
{
    USART_SendData(USART1, data);
    while (USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);
}

// printf 重定向到 USART1
int fputc(int ch, FILE *f)
{
    USART1_SendByte((uint8_t)ch);
    return ch;
}

int main(void)
{
    USART1_Config();
    printf("STM32 USART1 Ready!\r\n");
    printf("Clock: %d MHz\r\n", SystemCoreClock / 1000000);
    while (1);
}