I2C for PIC Microcontrollers

				
					#include <pic16f877a.h>
#include <xc.h>

// Define the frequency of the external crystal oscillator
#define _XTAL_FREQ 20000000  // 20MHz external crystal oscillator frequency
unsigned char RX_Data = 0x00;
unsigned char TX_Data = 0x00;

void I2C_Slave_Init(unsigned char SlaveAddress);

void main()
{
    I2C_Slave_Init(0x48); // The address should correspond to where the master is sending it to
    
    while(1)
    {
        // Do something with incoming RX_Data here
    }
}

// end main ------------------------------------------------

void I2C_Slave_Init(unsigned char SlaveAddress) {
    TRISB0 = 1; // SDA pin set as input
    TRISB1 = 1; // SCL pin set as input

    SSPADD = SlaveAddress << 1; // Set I2C Device 7-bit Address 
    SSPSTAT = 0x80;   // Disable Slew Rate Control (Standard Mode)
    SSPCON1 = 0x36;   // Enable I2C, Slave mode, other bits are cleared
    SSPCON2 = 0x01;   // Enable Clock Stretching

    // Enable interrupts
    SSPIE = 1;        // Enable I2C interrupt
    SSPIF = 0;        // Clear the I2C interrupt flag right from the start
    PEIE = 1;         // Enable Peripheral Interrupt
    GIE = 1;          // Enable Global Interrupt
}

void __interrupt() ISR(void)
{
    if(PIR1.SSPIF) // Check if I2C interrupt flag is set
    {
            // Check if it's a Read operation
            if (!SSPSTAT.R_nW)
            {
                while(!SSPSTAT.BF);     // Wait until buffer is full
                RX_Data = SSPBUF;       // Read The Received Data Byte
                SSPCON.CKP = 1;         // Release Clock Line SCL
            }
            else // Check if it's a Write operation
            {
                BF = 0;                 // Clear buffer full flag
                SSPBUF = TX_Data;       // Write Your Data
                SSPCON.CKP = 1;         // Release Clock Line SCL
                while(SSPSTAT.BF);      // Wait until buffer is empty
            }
        }
        PIR1.SSPIF = 0;  // Clear the I2C interrupt flag
    }
}