PIC16F7X I2C Issues With 24AA01/24LC01B EEPROM

Question

I have an existing PCB that is no longer supported by the manufacturer and has been plagued with software issues for years. So i don't have much control over how the board is laid out and what components are used.

The board has a PIC16F747 running on the internal oscillator at 8Mhz, and a 24AA01 EEPROM chip with 1k ohm pullups (to 5v).

I have had no problem with any other aspects of the PIC, ive got ADC and PWM working fine but i just cannot get I2C communication to work as expected.

All I2C commands are being accepted but I'm not getting the data i have written back as I expected.

I know the EEPROM is working as i can interface with the chip using a AVR MCU using a PCB header that has connections to the I2C bus.

The next port of call is for me to invest in a oscilloscope or I2C buss sniffer so i can actually see what is being sent.

Here is some stripped down code of what I'm trying to achieve.

#pragma config FOSC = INTOSCIO  // Oscillator Selection bits (INTRC oscillator; port I/O function on OSC1/CLKI/RA7 and OSC2/CLKO/RA6)
#pragma config WDTE = OFF        // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = OFF      // MCLR/VPP/RE3 Pin Function Select bit (MCLR/VPP/RE3 pin function is digital input only, MCLR gated to '1')
#pragma config BOREN = ON       // Brown-out Reset Enable bit (Enabled)
#pragma config BORV = 20        // Brown-out Reset Voltage bits (VBOR set to 2.0V)
#pragma config CCP2MX = RC1     // CCP2 Multiplex bit (CCP2 is on RC1)
#pragma config CP = OFF         // Flash Program Memory Code Protection bits (Code protection off)

// CONFIG2
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enable bit (Fail-Safe Clock Monitor enabled)
#pragma config IESO = ON        // Internal External Switchover bit (Internal External Switchover mode enabled)
#pragma config BORSEN = ON      // Brown-out Reset Software Enable bit (Enabled)

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



#define _XTAL_FREQ 8000000

#include <xc.h>

void i2c_wait(){
    while (!SSPIF);
    SSPIF = 0;

    while ((SSPCON2 & 0b00011111)    ||    (SSPSTAT & 0b00000100));
}


int address = 0x01; // Address to write to
int value = 0x11; // Value to write
int result = 0x00; // Result returned from SSPBUF

void main(void) {

    // Set Internal Oscillator to 8Mhz
    OSCCONbits.IRCF = 0x7;


    // Setup EEPROM Write Enable
    TRISA4 = 0;
    RA4 = 0;

    // Setup output for testing
    TRISD6 = 0;
    RD6 = 0;

    // Set SDA & SCL to  inputs
    TRISC3 = 1;
    TRISC4 = 1;


    SSPCONbits.SSPM = 0x8; // i2c Master mode
    SSPADD = 4; // Set Clock for 400k
    SSPEN = 1; // Enable SSP Module

    while(1)        
    {       
        // Init Interrupt
        SSPIF = 0;

        // Write Data
        // Start    
        SEN = 1;        
        i2c_wait();
        // Send Addres + W      
        SSPBUF = 0xA0;
        i2c_wait();
        // Send EEPROM Address      
        SSPBUF = address;
        i2c_wait();
        // Send Data to set in address      
        SSPBUF = value;
        i2c_wait();
        // Send Stop        
        PEN = 1;
        i2c_wait();     

        // Let EEPROM Settle
        __delay_ms(10);

        // Read Data
        // Start
        SEN = 1;
        i2c_wait();
        // Send Address + W 
        SSPBUF = 0xA0;
        i2c_wait();
        // Send EEPROM Address      
        SSPBUF = address;
        i2c_wait();
        // Repeat Start     
        RSEN = 1;
        i2c_wait();
        // Send Address + R     
        SSPBUF = 0xA1;
        i2c_wait();
        // Read Data        
        RCEN = 1;
        i2c_wait();
        result = (SSPBUF);
        // Set NACK     
        ACKDT = 1;
        ACKEN = 1;
        i2c_wait();
        // Stop     
        PEN = 1;
        i2c_wait();                             


        // Let see what we got then!
        if (result < 0x22){
            RD6 = 1;
        } 
        else
        {
            RD6 = 0;
        }

        // Settle 
        __delay_ms(10);

    }   
    return; 
}
```