e2prom_c.c

E2PROM 24C02的驱动程序

#include "config.h"
#include "e2prom.h"
#include "common.h"

/*C51 standard include file.*/
#include <reg52.h>
#include <intrins.h>

/***************************************************************************/
#define WriteDeviceAddress 0xa0 /*MSB: 10100000*/
#define ReadDviceAddress 0xa1 /*MSB: 10100001*/
#define NOP5() _nop_();_nop_();_nop_();_nop_();_nop_()
/***************************************************************************/

sbit    Data = P1^0;
sbit    CLK =  P1^1;


/*Start is identified by a falling edge of Serial Data(Data) while Serial Clock (CLK) is stable in the
    High state.*/
void start24c02() {
    Data=1;
    NOP5();
    CLK=1;
    NOP5();
    Data=0;
    NOP5();
    CLK=0;
    NOP5();
}

/*Stop is identified by a rising edge of Serial Data(Data) while Serial Clock (CLK) is stable and driven
    High.*/
void stop24c02() {
    Data=0;
    NOP5();
    CLK=1;
    NOP5();
    Data=1;
    NOP5();
    CLK=0;
    NOP5();
}

/**/
void ack() {
    Data=0;
    NOP5();
    CLK=1;
    NOP5();
    CLK=0;
    NOP5();
    Data=1;
}

/***************************************************************************/
void noAck()
{
    Data=1;
    NOP5();
    CLK=1;
    NOP5();
    CLK=0;
    NOP5();
}

/***************************************************************************/
bit checkAck(void)
{
    bit ErrorBit;
    Data = 1;
    NOP5();
    CLK = 1;
    NOP5();
    ErrorBit = Data;
    NOP5();
    CLK=0;
    return(ErrorBit);
}

/*Write 8 bit data/instruction to I2C device.*/
void write8Bit(unsigned char input) {
    unsigned char temp;
    for ( temp=8; temp > 0; temp--)
    {
        Data = (bit)(input&0x80);
        NOP5();
        CLK = 1;
        NOP5();
        CLK = 0;
        NOP5();
        input = input<<1;
    }
}


/* return number of bytes written.
 */
U8 e2promWrite(U8 offset, U8 *buf, U8 size)
{
    U8 writtenNum = 0;
    bit ackValue = 1;
    selectClock(6);
    start24c02();
    write8Bit(WriteDeviceAddress);
    ackValue = checkAck();
    if ( ackValue != 0 )
    {
        return writtenNum;
    }
    write8Bit(offset);
    ackValue = checkAck();
    if ( ackValue != 0 )
    {
        return writtenNum;
    }
    for ( ; size > 0; size-- )
    {
        write8Bit(*buf);
        ackValue = checkAck();
        if ( ackValue != 0 )
        {
            return writtenNum;
        }
        writtenNum++;
        buf++;
    }
    stop24c02();
    return writtenNum;
}

/*Read 8 bit data from I2C device.*/
unsigned char read8Bit()
{
    unsigned char temp, rbyte=0;
    for ( temp=8; temp > 0; temp-- )
    {
        CLK = 1;
        rbyte = rbyte << 1;
        rbyte = rbyte|((unsigned char)(Data));
        CLK=0;
    }
    return(rbyte);
}

/* return number of bytes written. */
U8 e2promRead(U8 offset, U8 *buf, U8 size)
{
    U8 readData = 0;
    bit ackValue = 1;
    selectClock(6);
    start24c02();
    write8Bit(WriteDeviceAddress);
    ackValue = checkAck();
    if ( ackValue != 0 )
    {
        return readData;
    }
    write8Bit(offset);
    ackValue = checkAck();
    if ( ackValue != 0 )
    {
        return readData;
    }
    start24c02();   
    write8Bit(ReadDviceAddress);
    ackValue = checkAck();
    if ( ackValue != 0 )
    {
        return readData;
    }
    while ( size > 1 )
    {
        *buf = read8Bit();
        ack();
        readData++;
        buf++;
        size--;
    }
    *buf = read8Bit();
    noAck();
    readData++;
    stop24c02();
    return readData;
}