usart.h
#ifndef _USART_H
#define _USART_H
#include "stm32f10x.h"
#include "stdio.h"
void Usart_Init(unsigned long int Rate);
int fputc(int ch, FILE *f);
#endif


pbdata.h
#ifndef _PBDATA_H
#define _PBDATA_H
#include "stm32f10x.h"
void RCC_Init(unsigned char PLL);
#endif


usart.c
#include "usart.h"
void Usart_Init(unsigned long int Rate)
{
        unsigned short int M,F;
        float temp;
        temp=(float)(72000000)/(16*Rate);
        M=temp;
        F=(temp-M)*16;
        USART1->BRR=(M<<4)+F;
        USART1->CR1|=1<<13;
        USART1->CR1|=0X03<<2;
        GPIOA->CRH&=0XFFFFF00F;
        GPIOA->CRH|=0X000004b0;
        RCC->APB2ENR|=1<<2;
        RCC->APB2ENR|=1<<14;
        RCC->APB2ENR|=0x01;
}

int fputc(int ch, FILE *f)
{
        USART1->DR=(unsigned char)ch;
        while(!(USART1->SR&(1<<6)));
        return ch;
}


pbdata.c
#include "pbdata.h"
void RCC_Init(unsigned char PLL)
{       
        RCC->CR|=1<<16;
        while(!(RCC->CR&(1<<17)));
        RCC->CFGR|=1<<10;
        RCC->CFGR|=(PLL-2)<<18;
        RCC->CFGR|=1<<16;
        FLASH->ACR=0X32;
        RCC->CR|=1<<24;
        while(!(RCC->CR&(1<<25)));
        RCC->CFGR|=0X02;
        while((RCC->CFGR&0X08)!=0X08);
}


main.c
#include "stm32f10x.h"
#include "pbdata.h"
#include "usart.h"
int main(void)
{
        RCC_Init(9);  //系统时钟初始化
        Usart_Init(115200); //串口初始化
        printf("1234567");
        while(1);
}


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