#include <reg51.h>
#include "eeprom.h"


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

void delay()
{
	unsigned char i,j;

	for( i=0; i<100; i++)
	{
		for( j=0; j<10; j++)
			;
	}

}

void StopI2C(void) 
{

	SDA = 0;
	SCL = 1;
	SDA = 1;
	SCL = 0;
}


void StartI2C(void) 
{

	SDA = 1;
	SCL = 1;
	SDA = 0;
	SCL = 0;
}

void WriteI2C(bit val) 
{

	SDA = val;
	SCL = 1;
	SCL = 0;
}

bit ReadI2C(void) 
{

	bit val;

	SDA = 1;
	SCL = 1;
	val = SDA;
	SCL = 0;
	return val;
}
//writing a byte to eeprom
void writeByte(unsigned char val, unsigned int address) 
{
	unsigned char i;

	/* device address */
	StartI2C();
	WriteI2C(1);
	WriteI2C(0);
	WriteI2C(1);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	ReadI2C();

	/* page address */
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(address & 0x1000);
	WriteI2C(address & 0x0800);
	WriteI2C(address & 0x0400);
	WriteI2C(address & 0x0200);
	WriteI2C(address & 0x0100);
	ReadI2C();

  	WriteI2C(address & 0x0080);
	WriteI2C(address & 0x0040);
	WriteI2C(address & 0x0020);
	WriteI2C(address & 0x0010);
	WriteI2C(address & 0x0008);
	WriteI2C(address & 0x0004);
	WriteI2C(address & 0x0002);
	WriteI2C(address & 0x0001);
	ReadI2C();
	//write a byte
	for(i=0; i<8; i++) 
	{
		WriteI2C(((val & (0x01 << i)) == 0) ? 0 : 1);
	}
	ReadI2C();
	StopI2C();

	delay();
	delay();
}
//reading byte from eeprom
unsigned char readByte(unsigned int address) 
{

	unsigned char i,j;

	StartI2C();
	WriteI2C(1);
	WriteI2C(0);
	WriteI2C(1);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	ReadI2C();

	/* page address */
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(address & 0x1000);
	WriteI2C(address & 0x0800);
	WriteI2C(address & 0x0400);
	WriteI2C(address & 0x0200);
	WriteI2C(address & 0x0100);
	ReadI2C();

  	WriteI2C(address & 0x0080);
	WriteI2C(address & 0x0040);
	WriteI2C(address & 0x0020);
	WriteI2C(address & 0x0010);
	WriteI2C(address & 0x0008);
	WriteI2C(address & 0x0004);
	WriteI2C(address & 0x0002);
	WriteI2C(address & 0x0001);
	ReadI2C();

	/* device address */
	StartI2C();
	WriteI2C(1);
	WriteI2C(0);
	WriteI2C(1);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(0);
	WriteI2C(1);
	ReadI2C();

	// read a byte 
	for(i=j=0; i<8; i++) 
	{
	   j |= (unsigned char)ReadI2C() << i;
	}
	WriteI2C(1);
	StopI2C();
	
	return j;
}
//enters a new message to eeprom
void newMessage(unsigned char *mydata, unsigned int count)
{
	unsigned int x;
	unsigned int address = ((count-1)*45) + 131;
	
	for(x=0; x<45; x++)
	{
		writeByte(mydata[x],address++);
	}

}
//enters a new password into the eeprom
void newPassword(unsigned char *mydata, unsigned int count)
{
	unsigned int x;
	unsigned int address = (count*4) + 2;
	
	for(x=0; x<4; x++)
	{
		writeByte(mydata[x],address++);
	}

}
//retevies a message from eeprom
void getMessage(unsigned char *mydata, unsigned int count)
{
	unsigned int x;
	unsigned int address = ((count-1)*45) + 131;

	for(x=0; x<45; x++)
	{
		mydata[x] = readByte(address++);
	}

}
//return the total of the number passwords and messages
unsigned int getTotals(unsigned int address)
{
	return(readByte(address));
}
//updates the total of passwords and messages
void updateTotals(unsigned int mydata, unsigned int address)
{
	writeByte(mydata,address);
}
//check to see if password is valid or not
unsigned char checkPassword(unsigned char *password, unsigned int passTotal)
{
	unsigned int x,count = 0;
	unsigned char pass[4];
	unsigned int address = 2;

	do
	{
		//reading in one password and check
		for(x=0; x<4; x++)
		{
			pass[x] = readByte(address++);
		}
		if( password[0] == pass[0] && password[1] == pass[1] &&
			password[2] == pass[2] && password[3] == pass[3] )
		{
			count = passTotal + 3;
		}
		else
		{
			count++;
		}
	}
	while(count < passTotal);

	if(count == passTotal + 3)
	{   return 0;   }
	else
	{	return 1;	}

}