myiic.c

基于stm32的MP3播放器

#include"myiic.h"
//STM32软件模拟IIC，STM32的硬件IIC太难用了！
//能很好的支持FM24C16&PT2314&TEA5767		    					  
//正点原子@SCUT
//V1.0
	 
//us延时函数
void delay(u8 nus)
{
	u16 i;
	while(nus--)for(i=15;i>0;i--);
}
//初始化IIC
//CHECK OK 09/05/18
void IIC_Init(void)
{					     
 	RCC->APB2ENR|=0X00000008;//先使能外设IO PORTB时钟 							 
	GPIOB->CRH&=0XFFFF00FF;//PB10/11 推挽输出
	GPIOB->CRH|=0X00003300;	   
	GPIOB->ODR|=0X0C00;    //0-2 输出高
}
//产生IIC起始信号
//CHECK OK 09/05/18
void IIC_Start(void)
{
	SDA_OUT();     //sda线输出
	IIC_SDA_SET(1);	  	  
	IIC_SCL_SET(1);
	delay(4);
 	IIC_SDA_SET(0);//START:when CLK is high,DATA change form high to low 
	delay(4);
	IIC_SCL_SET(0);//钳住I2C总线，准备发送或接收数据 
}	  
//产生IIC停止信号
//CHECK OK 09/05/18
void IIC_Stop(void)
{
	SDA_OUT();//sda线输出
	IIC_SCL_SET(0);
	IIC_SDA_SET(0);//STOP:when CLK is high DATA change form low to high
 	delay(4);
	IIC_SCL_SET(1); 
	IIC_SDA_SET(1);//发送I2C总线结束信号							   	
}
//等待应答信号到来
//返回值：0，接收应答失败
//        1，接收应答成功
//CHECK OK 09/05/18
u8 IIC_Wait_Ack(void)
{
	u8 ucErrTime=0;
	SDA_IN();      //SDA设置为输入  
	IIC_SDA_SET(1);delay(1);	   
	IIC_SCL_SET(1);	 
	while(READ_SDA())
	{
		ucErrTime++;
		if(ucErrTime>250)
		{
			IIC_Stop();
			return 0;
		}
	}
	IIC_SCL_SET(0);//时钟输出0 	   
	return 1;  
} 
//产生ACK应答
//CHECK OK 09/05/18
void IIC_Ack(void)
{
	IIC_SCL_SET(0);
	SDA_OUT();
	IIC_SDA_SET(0);
	delay(1);
	IIC_SCL_SET(1);
	delay(1);
	IIC_SCL_SET(0);
}
//不产生ACK应答
//CHECK OK 09/05/18
void IIC_NAck(void)
{
	IIC_SCL_SET(0);
	SDA_OUT();
	IIC_SDA_SET(1);
	delay(1);
	IIC_SCL_SET(1);
	delay(1);
	IIC_SCL_SET(0);
}					 				     
//IIC发送一个字节
//返回从机有无应答
//1，有应答
//0，无应答
//CHECK OK 09/05/18
void IIC_Send_Byte(u8 txd)
{                        
    u8 t;   
	SDA_OUT(); 	    
    IIC_SCL_SET(0);//拉低时钟开始数据传输
    for(t=0;t<8;t++)
    {              
        IIC_SDA_SET((txd&0x80)>>7);
        txd<<=1; 	  
		delay(1);   //对TEA5767这三个延时都是必须的
		IIC_SCL_SET(1);
		delay(1); 
		IIC_SCL_SET(0);	
		delay(1);
    }	 
} 	    
//读1字节，ack=1时，发送ACK，ack=0，发送nACK
//CHECK OK 09/05/18
u8 IIC_Read_Byte(unsigned char ack)
{
	unsigned char i,receive=0;
	SDA_IN();//SDA设置为输入
    for(i=0;i<8;i++ )
	{
        IIC_SCL_SET(0); 
        delay(1);
		IIC_SCL_SET(1);
        receive<<=1;
        if(READ_SDA())receive++;    
    }					 
    if (!ack)
        IIC_NAck();//发送nACK
    else
        IIC_Ack(); //发送ACK   
    return receive;
}