// PIC16F877A Configuration Bit Settings
// 'C' source line config statements
#include <xc.h>
#include <pic16f877a.h>

#define _XTAL_FREQ 8000000

// #pragma config statements should precede project file includes.
// Use project enums instead of #define for ON and OFF.

// CONFIG
#pragma config FOSC = XT   // Oscillator Selection bits (XT oscillator)
#pragma config WDTE = OFF  // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = OFF // Brown-out Reset Enable bit (BOR disabled)
#pragma config LVP = OFF   // Low-Voltage In-Circuit Serial Programming Enable bit
#pragma config CPD = OFF   // Data EEPROM Memory Code Protection bit
#pragma config WRT = OFF   // Flash Program Memory Write Enable bits
#pragma config CP = OFF    // Flash Program Memory Code Protection bit

void I2C_Master_Init(const unsigned long c)
{
  SSPCON = 0b00101000;
  SSPCON2 = 0;
  SSPADD = (_XTAL_FREQ/(4*c))-1;
  SSPSTAT = 0;
  TRISC3 = 1;        //Setting as input as given in datasheet
  TRISC4 = 1;        //Setting as input as given in datasheet
}

void I2C_Master_Wait()
{
  while ((SSPSTAT & 0x04) || (SSPCON2 & 0x1F));
}

void I2C_Master_Start()
{
  I2C_Master_Wait();
  SEN = 1;
}

void I2C_Master_RepeatedStart()
{
  I2C_Master_Wait();
  RSEN = 1;
}

void I2C_Master_Stop()
{
  I2C_Master_Wait();
  PEN = 1;
}

void I2C_Master_Write(unsigned d)
{
  I2C_Master_Wait();
  SSPBUF = d;
}

unsigned short I2C_Master_Read(unsigned short a)
{
  unsigned short temp;
  I2C_Master_Wait();
  RCEN = 1;
  I2C_Master_Wait();
  temp = SSPBUF;
  I2C_Master_Wait();
  ACKDT = (a)?0:1;
  ACKEN = 1;
  return temp;
}

void main()
{
  nRBPU = 0;                    //Enable PORTB internal pull up resistor
  TRISB = 0xFF;                 //PORTB as input
  TRISD = 0x00;                 //PORTD as output
  PORTD = 0x00;                 //All LEDs OFF
  I2C_Master_Init(100000);      //Initialize I2C Master with 100KHz clock
  while(1)
  {
    I2C_Master_Start();         //Start condition
    I2C_Master_Write(0x30);     //7 bit address + Write
    I2C_Master_Write(PORTB);    //Write data
    I2C_Master_Stop();          //Stop condition
    __delay_ms(200);
    I2C_Master_Start();         //Start condition
    I2C_Master_Write(0x31);     //7 bit address + Read
    PORTD = I2C_Master_Read(0); //Read + Acknowledge
    I2C_Master_Stop();          //Stop condition
    __delay_ms(200);
  }
}