spi.h

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// SPI总线速度设置 
#define SPI_SPEED_2   0
#define SPI_SPEED_4   1
#define SPI_SPEED_8   2
#define SPI_SPEED_16  3
#define SPI_SPEED_32  4
#define SPI_SPEED_64  5
#define SPI_SPEED_128 6
#define SPI_SPEED_256 7

//SPIx 读写一个字节
//TxData:要写入的字节
//返回值:读取到的字节
unsigned char SPIx_ReadWriteByte(unsigned char TxData)
{		
	unsigned char retry=0;				 
	while((SPI1->SR&1<<1)==0)//等待发送区空	
	{
		retry++;
		if(retry>200)return 0;
	}			  
	SPI1->DR=TxData;	 	  //发送一个byte 
	retry=0;
	while((SPI1->SR&1<<0)==0) //等待接收完一个byte  
	{
		retry++;
		if(retry>200)return 0;
	}	  						    
	return SPI1->DR;          //返回收到的数据				    
}

void SPIx_Init(void)
{	 
	RCC->APB2ENR|=1<<2;       //PORTA时钟使能 	 
	RCC->APB2ENR|=1<<12;      //SPI1时钟使能 
		   
	//这里只针对SPI口初始化
	GPIOA->CRL&=0X000FFFFF; 
	GPIOA->CRL|=0XBBB00000;//PA5.6.7复用 	    
	GPIOA->ODR|=0X7<<5;    //PA5.6.7上拉
		
	SPI1->CR1|=0<<10;//全双工模式	
	SPI1->CR1|=1<<9; //软件nss管理
	SPI1->CR1|=1<<8;  

	SPI1->CR1|=1<<2; //SPI主机
	SPI1->CR1|=0<<11;//8bit数据格式	
	SPI1->CR1|=1<<1; //空闲模式下SCK为1 CPOL=1
	SPI1->CR1|=1<<0; //数据采样从第二个时间边沿开始,CPHA=1  
	SPI1->CR1|=3<<3; //Fsck=Fcpu/256
	SPI1->CR1|=0<<7; //MSBfirst   
	SPI1->CR1|=1<<6; //SPI设备使能
	SPIx_ReadWriteByte(0xff);//启动传输		 
}   
//SPI 速度设置函数
//SpeedSet:
//SPI_SPEED_2   2分频   (SPI 36M@sys 72M)
//SPI_SPEED_8   8分频   (SPI 9M@sys 72M)
//SPI_SPEED_16  16分频  (SPI 4.5M@sys 72M)
//SPI_SPEED_256 256分频 (SPI 281.25K@sys 72M)
void SPIx_SetSpeed(unsigned char SpeedSet)
{
	SPI1->CR1&=0XFFC7;//Fsck=Fcpu/256
	if(SpeedSet==SPI_SPEED_2)//二分频
	{
		SPI1->CR1|=0<<3;//Fsck=Fpclk/2=36Mhz	
	}else if(SpeedSet==SPI_SPEED_8)//八分频 
	{
		SPI1->CR1|=2<<3;//Fsck=Fpclk/8=9Mhz	
	}else if(SpeedSet==SPI_SPEED_16)//十六分频
	{
		SPI1->CR1|=3<<3;//Fsck=Fpclk/16=4.5Mhz
	}else			 	 //256分频
	{
		SPI1->CR1|=7<<3; //Fsck=Fpclk/256=281.25Khz 低速模式
	}
	SPI1->CR1|=1<<6; //SPI设备使能	  
} 

//初始化SPI FLASH的IO口
void SPI_Flash_Init(void)
{
	RCC->APB2ENR|=1<<2;       //PORTA时钟使能 	    
	//这里 
	GPIOA->CRL&=0XFFF000FF; 
	GPIOA->CRL|=0X00033300;//PA2.3.4 推挽 	    
	GPIOA->ODR|=0X7<<2;    //PA2.3.4上拉
	SPIx_Init();		   //初始化SPI
}