STM32软件IIC速度

如题，我把IIC里面的延时函数屏蔽为空函数
void SYSTICK_DelayUs(unsigned int Del_1ms)
{
// unsigned char j;
// while(Del_1ms–)
// {
// for(j=0;j<255;j++);
// }
}
1uS都不延时，居然跑得飞起，闭环速度提升了二三十倍；
然后用示波器测SCL波形看速度，如下图



如图2所示，算出来的速度好像是900多kHz,(两脉冲间隔大概1.08us)
哇！！！这么爽的吗！！！
（以下代码为沁和智能提供的AS5600驱动代码）

```c
#include "./AS5600IIC/AS5600.h"

														
	


 
 void SYSTICK_DelayUs(unsigned int Del_1ms)
{
//	unsigned char j;
//	while(Del_1ms--)
//	{	
//		for(j=0;j<255;j++);
//	}
}
void IIC_Init_AS5600(void)
{					     
	GPIO_InitTypeDef GPIO_InitStructure;
	RCC_APB2PeriphClockCmd(	RCC_APB2Periph_GPIOB, ENABLE );	
	   
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10|GPIO_Pin_11;
	GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP ;  																		 //ÍÆÍìÊä³ö
	GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
	GPIO_Init(GPIOB, &GPIO_InitStructure);
	GPIO_SetBits(GPIOB,GPIO_Pin_10|GPIO_Pin_11); 																					//PB10,PB11 Êä³ö¸ß
}

 
void IIC_Start_AS5600(void)
{
	SDA_OUT();     																																					//sdaÏßÊä³ö
	IIC_SDA=1;	  	  
	IIC_SCL=1;
	SYSTICK_DelayUs(4);
 	IIC_SDA=0;																																							//START:when CLK is high,DATA change form high to low 
	SYSTICK_DelayUs(4);
	IIC_SCL=0;																																							//ǯסI2C×ÜÏߣ¬×¼±¸·¢ËÍ»ò½ÓÊÕÊý¾Ý 
}	  


void IIC_Stop_AS5600(void)
{
	SDA_OUT();																																							//sdaÏßÊä³ö
	IIC_SCL=0;
	IIC_SDA=0;																																							//STOP:when CLK is high DATA change form low to high
	SYSTICK_DelayUs(4);
	IIC_SCL=1; 
	IIC_SDA=1;																																							//·¢ËÍI2C×ÜÏß½áÊøÐźÅ
	SYSTICK_DelayUs(4);
}


u8 IIC_Wait_Ack_AS5600(void)
{
	u8 ucErrTime=0;
	SDA_IN();      																																				//SDAÉèÖÃΪÊäÈë  
	IIC_SDA=1;
	SYSTICK_DelayUs(1);
	IIC_SCL=1;
	SYSTICK_DelayUs(1);	
	while(READ_SDA)
	{
		ucErrTime++;
		if(ucErrTime>250)
		{
			IIC_Stop_AS5600();
			return 1;
		}
	}
	IIC_SCL=0;																																					//ʱÖÓÊä³ö0 	   
	return 0;  
} 


void IIC_Ack(void)
{
	IIC_SCL=0;
	SDA_OUT();
	IIC_SDA=0;
	SYSTICK_DelayUs(2);
	IIC_SCL=1;
	SYSTICK_DelayUs(2);
	IIC_SCL=0;
}


void IIC_NAck(void)
{
	IIC_SCL=0;
	SDA_OUT();
	IIC_SDA=1;
	SYSTICK_DelayUs(2);
	IIC_SCL=1;
	SYSTICK_DelayUs(2);
	IIC_SCL=0;
}					 				     


void IIC_Send_Byte(u8 txd)
{                        
    u8 t;   
		SDA_OUT(); 	    
    IIC_SCL=0;																																										//À­µÍʱÖÓ¿ªÊ¼Êý¾Ý´«Êä
    for(t=0;t<8;t++)
    {              
																																																	//IIC_SDA=(txd&0x80)>>7;
		if((txd&0x80)>>7)
			IIC_SDA=1;
		else
			IIC_SDA=0;
		txd<<=1; 	  
		SYSTICK_DelayUs(2);
		IIC_SCL=1;
		SYSTICK_DelayUs(2);
		IIC_SCL=0;	
		SYSTICK_DelayUs(2);
    }	 
} 	    


u8 IIC_Read_Byte(unsigned char ack)
{
	unsigned char i,receive=0;
	SDA_IN();																																														//SDAÉèÖÃΪÊäÈë
  for(i=0;i<8;i++ )
	{
    IIC_SCL=0; 
		SYSTICK_DelayUs(2);
		IIC_SCL=1;
    receive<<=1;
    if(READ_SDA)receive++;   
		SYSTICK_DelayUs(1);
  }					 
    if (!ack)
        IIC_NAck();																																									//·¢ËÍnACK
    else
        IIC_Ack(); 																																									//·¢ËÍACK   
    return receive;
}
u8 AS5600_IIC_Read_OneByte(u8 deviceaddr,u8 readaddr)
{
  u8 temp;
  IIC_Start_AS5600();
  IIC_Send_Byte(deviceaddr&0xfe);
  IIC_Wait_Ack_AS5600();
  IIC_Send_Byte(readaddr);
  IIC_Wait_Ack_AS5600();

  IIC_Start_AS5600();
  IIC_Send_Byte(deviceaddr|0x01);
  IIC_Wait_Ack_AS5600();
  temp=IIC_Read_Byte(0);
  IIC_Stop_AS5600();
  return temp;
}


int get_angle_SRC(void)
{
	int angle_SRC_inter;
			angle_SRC_inter =  AS5600_IIC_Read_OneByte((0x36<<1),0x0e);   
      angle_SRC_inter <<= 8;
			angle_SRC_inter |= AS5600_IIC_Read_OneByte((0x36<<1),0x0f); 
	return angle_SRC_inter;
}