u8 MPU_Write_Len(u8 addr,u8 reg,u8 len,u8 *buf)
{
u8 i; 
    IIC_Start(); 
IIC_Send_Byte((addr<<1)|0);//·????÷?????·+???ü??
if(IIC_Wait_Ack()) //????????
{
IIC_Stop();  
return 1;
}
    IIC_Send_Byte(reg); //???????÷???·
    IIC_Wait_Ack(); //????????
for(i=0;i<len;i++)
{
IIC_Send_Byte(buf); //·???????
if(IIC_Wait_Ack()) //????ACK
{
IIC_Stop();  
return 1;  
}
}    
    IIC_Stop();  
return 0;
} 
//IIC??????
//addr:?÷?????·
//reg:?????????????÷???·
//len:?????????¤??
//buf:??????????????????
//·?????:0,????
//    ????,?í?ó?ú??
u8 MPU_Read_Len(u8 addr,u8 reg,u8 len,u8 *buf)
{ 
  IIC_Start(); 
IIC_Send_Byte((addr<<1)|0);//·????÷?????·+???ü??
if(IIC_Wait_Ack()) //????????
{
IIC_Stop();  
return 1;
}
    IIC_Send_Byte(reg); //???????÷???·
    IIC_Wait_Ack(); //????????
    IIC_Start();
IIC_Send_Byte((addr<<1)|1);//·????÷?????·+???ü??
    IIC_Wait_Ack(); //???????? 
while(len)
{
if(len==1)*buf=IIC_Read_Byte(0);//??????,·???nACK 
else *buf=IIC_Read_Byte(1); //??????,·???ACK  
len--;
buf++; 
}    
    IIC_Stop(); //?ú?ú???????????? 
return 0;
}
//IIC??????×??? 
//reg:?????÷???·
//data:????
//·?????:0,????
//    ????,?í?ó?ú??
u8 MPU_Write_Byte(u8 reg,u8 data)  
{ 
    IIC_Start(); 
IIC_Send_Byte((AK8975_DEFAULT_ADDRESS<<1)|0);//·????÷?????·+???ü??
if(IIC_Wait_Ack()) //????????
{
IIC_Stop();  
return 1;
}
    IIC_Send_Byte(reg); //???????÷???·
    IIC_Wait_Ack(); //???????? 
IIC_Send_Byte(data);//·???????
if(IIC_Wait_Ack()) //????ACK
{
IIC_Stop();  
return 1;  
}  
    IIC_Stop();  
return 0;
}
//IIC??????×??? 
//reg:?????÷???· 
//·?????:??????????
u8 MPU_Read_Byte(u8 reg) //u8 MPU_Write_Byte(u8 reg,u8 data)
{
u8 res;
    IIC_Start(); 
IIC_Send_Byte((AK8975_DEFAULT_ADDRESS<<1)|0);//·????÷?????·+???ü??
IIC_Wait_Ack(); //???????? 
    IIC_Send_Byte(reg); //???????÷???·
    IIC_Wait_Ack(); //????????
    IIC_Start();
//IIC_Send_Byte((MPU_ADDR<<1)|1);//·????÷?????·+???ü??
    IIC_Wait_Ack(); //???????? 
res=IIC_Read_Byte(0);//????????,·???nACK 
    IIC_Stop(); //?ú?ú???????????? 
return res;
}




int main(void)
{ 

//short aacx,aacy,aacz; //???????????÷????????
//short gyrox,gyroy,gyroz; //??????????????
//short temp; //????


delay_init();  //?????????±????
uart_init(115200); //???????®???¨??????500000
  IIC_Init();

                                                    
  while(1)
{

delay_ms(5000);
 //count= MPU_Read_Byte(AK8975_RA_WIA);
//printf("%c",count);
//MPU_Read_Byte(AK8975_RA_INFO)
   // MPU_Write_Byte(AK8975_RA_CNTL,AK8975_MODE_SINGLE);
    delay_ms(10);
MPU_Read_Len(AK8975_DEFAULT_ADDRESS, AK8975_RA_HXL,6,buffer);

x=((u16)buffer[0]<<8)|buffer[1];
y=((u16)buffer[2]<<8)|buffer[3];
z=((u16)buffer[4]<<8)|buffer[5];

//x=(buffer[1]<<8)|buffer[0];
//y=(buffer[3]<<8)|buffer[2];
//z=(buffer[5]<<8)|buffer[4];




printf("%c%c%c",x,y,z);
}

}
为什么数据读不出来