i2c.c

单片机键值测定程序

/****************************************************************************
*                                                                           *
* 							I2C Driving Routines							*
*                                                                           *
****************************************************************************/
#include "define.h"
#include "global.h"
#include <regX52.H>
#include <intrins.h>

void I2C_BitDelay(void)
{
_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();_nop_();

}

/****************************************************************************
* Name: Send_I2C_Start
* Description: This function assumes that SCCLK and SDA are both high upon entrance,
 and generates the I2C start condition required for initiating
 communication
Return value: NONE
****************************************************************************/
void Send_I2C_Start(void)
{
	PIN_SDA=1;I2C_BitDelay(); PIN_SCL=1;
	I2C_BitDelay();

  	PIN_SDA=0;				// drive SDA low while SCCLK is high for I2C start
	I2C_BitDelay();

  	PIN_SCL=0;				// drive SCCLK low to prepare for data transfer
	I2C_BitDelay();
}


/****************************************************************************
* Name: Send_I2C_Stop
* Description: This function generates the I2C stop condition required for
 proper termination of I2C communication
Return value: NONE
****************************************************************************/
void Send_I2C_Stop(void)
{
	PIN_SDA=0;				//ensure that SDA is low
	I2C_BitDelay();
  	PIN_SCL=1;				//drive SCCLK high to prepare for I2C stop
	I2C_BitDelay();

  	PIN_SDA=1;				//SDA rising edge while SCCLK high = I2C stop
	I2C_BitDelay();

}

/***************************************************************************/
//法送确认信号

void SendAcknowledge(bit ack)
{

 PIN_SDA=ack;
 I2C_BitDelay();
 PIN_SCL=1;
 I2C_BitDelay();
 PIN_SCL=0;
}



/****************************************************************************
* Name: Write_I2C_Byte
* Description: 
 This function will write one byte through the parallel port in I2C serial 
 communication format. The SCCLK is assumed LOW upon entering this function, 
 and is left LOW upon exiting.
****************************************************************************/


bit Write_I2C_Byte(uchar mybyte){

register uchar i,t;				// bit counter
bit ack;
	for (i=0;i<8;i++){

        if(mybyte & 0x80)
		  {PIN_SDA=1;P2_3=0;}
		else {PIN_SDA=0;P2_3=1;}

		I2C_BitDelay();
		PIN_SCL=1;				// clock out
		for(t=0;t<12;t++)
		{

		I2C_BitDelay();
		}
		P2_2=0;
		for(t=0;t<1;t++)
		{

		I2C_BitDelay();
		}
		P2_2=1;
				for(t=0;t<12;t++)
		{

		I2C_BitDelay();
		}

		PIN_SCL=0;
		mybyte<<=1;
	}
		
	PIN_SDA=1;                 	// release SDA for ACK
	I2C_BitDelay();

		
	// ************* to get ACK ***************
	PIN_SCL=1;P2_2=0;
	I2C_BitDelay();
 
P2_2=1;

	PIN_SCL=0; 	
	I2C_BitDelay();if(PIN_SDA==0)ack=0;else ack=1;if(ack==1)P2_3=0;
	return ack;				// Received ACK, return 0


}


/****************************************************************************
; Name: Read_I2C_Byte
; Description: 
; This function will read one byte through I2C serial 
; communication format. The SCCLK is assumed LOW upon entering this function, 
; and is left LOW upon exiting.
;****************************************************************************/

uchar Read_I2C_Byte(void){
register uchar i;
uchar Byte;
	for(i=0;i<8;i++){
		PIN_SCL=1;
		I2C_BitDelay();	
        Byte<<=1;
        if(PIN_SDA)Byte=Byte | 0x01;
		I2C_BitDelay();
		PIN_SCL=0;
		I2C_BitDelay();
	

	}		

return Byte;
}