p8574.c

PCF8574 Remote 8-bit I/O expander for I2C-bus IO扩展芯片测试程序

#include <intrins.h>
#include <reg52.h>

sbit SCL=P3^7;
sbit SDA=P3^6;

void NOP(void);
void I2cStartBit(void);
void I2cStopBit(void);
void I2cSendAck(void);
void I2cSendNAck(void);
void I2cTestAck(void);
void I2cWriteByte(unsigned char OneByte);
unsigned char I2cReadByte(void);
void I2cWriteStringA(unsigned char slaw,unsigned char *Buffer,unsigned char Index);
void I2cWriteString(unsigned char slaw,unsigned char *Buffer,unsigned char Length);
void I2cReadString(unsigned char slar,unsigned char *Buffer,unsigned char Length);

void NOP(void)
{
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
   _nop_();
}

void I2cStartBit(void) //start the i2c bus
{
        SDA=1;
        SCL=1;
        NOP();
        SDA=0;
        NOP();
        SCL=0;
}

void I2cStopBit(void) //stop the i2c bus
{
        SDA=0;
        SCL=1;
        NOP();
        SDA=1;
        NOP();
        SCL=0;
}

void I2cSendAck(void) //send the answer bit
{
        SDA=0;
        SCL=1;
        NOP();
        SCL=0;
        SDA=1;
}

void I2cSendNAck(void) //send the not answer bit
{
        SDA=1;
        SCL=1;
        NOP();
        SCL=0;
        SDA=0;
}

void I2cTestAck(void) //test the answer bit
{
        SDA=1;
        SCL=1;
        F0=0;
        if(SDA==1)
        F0=1;
        SCL=0;
        NOP();
}

void I2cWriteByte(unsigned char OneByte) //send one byte to i2c bus
{
        unsigned char i;
        for(i=0;i<8;i++)
        {
                if((OneByte&0x80)>0)
                {
                        SDA=1;
                        SCL=1;
                        NOP();
                        NOP();
                        NOP();
                        NOP();
                        SCL=0;
                        SDA=0;
                }
                else
                {
                        SDA=0;
                        SCL=1;
                        NOP();
                        NOP();
                        NOP();
                        NOP();
                        SCL=0;
                }
        OneByte=OneByte<<1;
        }
}

unsigned char I2cReadByte(void)  //read one byte from i2c bus
{
        unsigned char nn=0xff,mm=0x80,uu=0x7f;
		unsigned char j;

        for(j=0;j<8;j++)
        {
                SDA=1;
                SCL=1;
                if(SDA==0)
                nn=(nn&uu);
                else
                nn=(nn|mm);
                nn=_crol_(nn,1);
                SCL=0;
        }

        return(nn);
}

void I2cWriteStringA(unsigned char slaw,unsigned char *Buffer,unsigned char Index)
{
        do
        {
                I2cStartBit();
                I2cWriteByte(slaw);
                I2cTestAck();
        }
        while(F0==1);
        I2cWriteByte(Buffer[Index]);
        I2cTestAck();
}

void I2cWriteString(unsigned char slaw,unsigned char *Buffer,unsigned char Length)  //send n bytes to i2c bus
{
        unsigned char k;
        do
        {
                I2cStartBit();
                I2cWriteByte(slaw);
                I2cTestAck();
        }
        while(F0==1);
        for(k=0;k<Length;k++)
        {
                I2cWriteByte(Buffer[k]); //////////////??????????
                I2cTestAck();
                while(F0==1)
                I2cWriteStringA(slaw,Buffer,k);
        }
        I2cStopBit();
}

void I2cReadString(unsigned char slar,unsigned char *Buffer,unsigned char Length)  //read n bytes from i2c bus
{
        unsigned char OneByte;
		unsigned char i;
        do
        {
                I2cStartBit();
                I2cWriteByte(slar);
                I2cTestAck();
        }
        while(F0==1);
        for(i=0;i<Length-1;i++)
        {
                OneByte=I2cReadByte();
                Buffer[i]=OneByte;
                I2cSendAck();
        }
        OneByte=I2cReadByte();
        Buffer[i]=OneByte;
        I2cSendNAck();
        I2cStopBit();
}

void main(void)
{
	//unsigned char temp3;
	unsigned char temp[2];
	temp[0]=0x55;
	temp[1]=0x55;
  	//PCF8574_Init();
  	while(1)
  	{
     	//temp3=IC_Read_Data();
		I2cWriteString(0x40,temp,2);
     	//Delay();
  	}
}