STM32F4 USART(RS485)发送与接收----(寄存器操作)

/*

 * Author                :固桐

 * History

 * --------------------

 * Rev                        : 0.00

 * Date                        : 01/06/2013

 *

 * create.

 * --------------------

 */

//-----------------Include files-------------------------//



#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <ctype.h>

#include <math.h>

#include <stdarg.h>

#include "stm32f4xx.h"

#include "..\include\usart.h"

#include "..\include\hardware.h"

//-----------------Variable------------------------------//



static int send_string_to_usart2(char * str);

static int send_byte_to_usart2(char data);

static int initialize_usart2(int baudrate);

static int my_printf_uart2(const char * fmt, ...);



//-----------------function------------------------------//



static int initialize_usart2(int baudrate)

{

         float temp;

u16 mantissa;

        u16 fraction; 

 

RCC->AHB1ENR |= 0x00000001; //open  A clock

RCC->APB1ENR &= 0xFFFDFFFF;

 RCC->APB1ENR |= 0x00020000;//open  usart2 clock

        



        GPIOA->MODER &= 0xFFFFFF0F; //

GPIOA->MODER |= 0x000000A0;      

     

 GPIOA->OSPEEDR &= 0xFFFFFFCF; //

 GPIOA->OSPEEDR |= 0x00000020;  

   

  GPIOA->PUPDR &= 0xFFFFFFCF; // 

  GPIOA->PUPDR |= 0x00000010;



    GPIOA->MODER &= 0xFFFFFFF3; //Configure RS485 DIR(PA.1)

    GPIOA->MODER |= 0x00000004; 

    GPIOA->OTYPER &= 0x0000FFFD; 

    GPIOA->PUPDR &= 0xFFFFFFF3;

    GPIOA->PUPDR |= 0x00000004; 

        

        GPIOA->OSPEEDR &= 0xFFFFFFF3;

        GPIOA->OSPEEDR |= 0x00000008;  

        

    GPIOA->AFR[0] |= 0x00007700; //Configure  (PA.2)(PA.3)

        

        temp = 42000000/ (16 * baudrate);      //串口使用APB1= 1/4CPU CLK=42M;

           

        temp=(float)(42*1000000)/(baudrate*16);//得到USARTDIV

        mantissa=floor(temp);                                 //得到整数部分

        fraction=(temp-mantissa)*16; //得到小数部分  

 mantissa<<=4;

        mantissa+=fraction; 

        USART2->BRR = mantissa;





 //-----------------相应的寄存器操作，参考RM0090数据手册------------------------------//

        USART2->CR1 &=~((1<<12) | (1<<10) );//0

 USART2->CR1 |= ((1<<3) | (1<<2) | (1<<8) | (1<<5)| (1<<13));//1

        

        USART2->CR2 &=~((1<<13)| (1<<12) | (1<<11)| (1<<10)| (1<<8) );

        USART2->CR2 |=(1<<9) ;

 

USART2->CR3 &=~((1<<8)| (1<<9)); 

        

        RS485_R;   //485芯片处于接收状态



        return 0;

}



 //-----------------发送字符------------------------------//

static int

send_byte_to_usart2(char data)

{

        RS485_T;



        USART2->DR= data;



        while (!(USART2->SR & 0x00000040 )) ;



        RS485_R;



        return 0;

}



 //-----------------发送字符串------------------------------//

static int

send_string_to_usart2(char * str)

{

        RS485_T;



        while (*str != '\0') {

                while (!((USART2->SR) & 0x00000040 )) ;

                USART2->DR = (*str++);

        }

        while (!(USART2->SR & 0x00000040 )) ;

        RS485_R;



        return 0;

}



 //-----------------中断接收------------------------------//

int

USART2_IRQHandler(void)

{

        

        while (!(USART2->SR & 0x00000020 )) ;

                        usart2.receive_buffer[usart2.receive_count++] = USART2->DR;

        if (usart2.receive_buffer[usart2.receive_count - 1] == '\n') {

                usart2.receive_buffer[usart2.receive_count - 1] = 0;

                usart2.receive_count = 0;

                usart2.receive_ok_flag = 1;

        }



        return 0;

}



 

static int

my_printf_uart2(const char * fmt, ...)

{

        va_list arg_ptr;

        char buf[BUFFER_SIZE];



        memset(buf, '\0', sizeof(buf));



        va_start(arg_ptr, fmt);

        vsprintf(buf, fmt, arg_ptr);

        va_end(arg_ptr);



        send_string_to_usart2(buf);



        return 0;

}