// gcc ssd1306.c -lwiringPi -o ssd1306

#include <stdio.h>
#include <string.h>
#include <wiringPiI2C.h>

#define WIDTH 128
#define HEIGHT 64

int buffer[ WIDTH * HEIGHT / 8 ];
int i2cd;

void ssd1306_command(unsigned int c)
{
    unsigned int control = 0x00;
    wiringPiI2CWriteReg8( i2cd, control, c );
}

void ssd1306_byte(unsigned int c)
{
    unsigned int control = 0x40;
    wiringPiI2CWriteReg8( i2cd, control, c );
}

void drawPixel( int x, int y, unsigned int color )
{
    switch (color)
    {
        case 1: // white
            buffer[x + ( y / 8 ) * WIDTH ] = 1;

            break;
        case 0: // black
            buffer[x + ( y / 8 ) * WIDTH ] = 0;
            break;
    }
}

void init()
{
    i2cd = wiringPiI2CSetup( 0x3C ); // address

    ssd1306_command(0xAE);          // 0xAE // display off
    ssd1306_command(0xD5);          // 0xD5 // set display clock division
    ssd1306_command(0x80);          // the suggested ratio 0x80
    ssd1306_command(0xA8);          // 0xA8 set multiplex
    ssd1306_command(63);            // set height
    ssd1306_command(0xD3);          // set display offset
    ssd1306_command(0x0);           // no offset
    ssd1306_command(64);            // line #0 setstartline
    ssd1306_command(0x8D);          // 0x8D // chargepump
    ssd1306_command(0x14);
    ssd1306_command(0x20);          // memory mode
    ssd1306_command(0x00);          // 0x0 act like ks0108
    ssd1306_command(161);           // segremap
    ssd1306_command(0xC8);          // comscandec
    ssd1306_command(0xDA);          // 0xDA set com pins
    ssd1306_command(0x12);
    ssd1306_command(0x81);          // 0x81 // set contract
    ssd1306_command(0xCF);
    ssd1306_command(0xD9);          // 0xd9 set pre-charge
    ssd1306_command(0xF1);
    ssd1306_command(0xDB);          // SSD1306_SETVCOMDETECT
    ssd1306_command(0x40);
    ssd1306_command(0xA4);          // 0xA4 // display all on resume
    ssd1306_command(0xA6);          // 0xA6 // normal display
    ssd1306_command(0x2E);          // deactivate scroll
    ssd1306_command(0xAF);          // --turn on oled panel
}

void renderBuffer(void)
{
    ssd1306_command(0x21);          // column address
    ssd1306_command(0);             // Column start address (0 = reset)
    ssd1306_command(127);           // Column end address (127
    ssd1306_command(0x22);          // page address
    ssd1306_command(0x00);          // Page start address (0 = reset)
    ssd1306_command(7);             // Page end address

    int i;

    for (i = 0; i < ( 128 * 64 / 8 ); i++)
    {
        ssd1306_byte( buffer[i] );
    }
}

void clearBuffer(void)
{
    memset( buffer, 0, ( 128 * 64 / 8 ) * sizeof( int ) );
}

void main()
{
    init();
    clearBuffer();
    drawPixel( 10, 10, 1 );
    renderBuffer();
}

#ifndef F_CPU
    #define F_CPU 8000000UL
#endif

#include <avr/io.h>
#include <util/delay.h>
#include <stdlib.h>
#include "i2c_master.c"
#include "i2c_master.h"

#define  SSD1306_ADDRESS 0x3C

void initDisplay()
{
    i2c_start(SSD1306_ADDRESS);

    i2c_write(0xAE);          // 0xAE // display off
    i2c_write(0xD5);          // 0xD5 // set display clock division
    i2c_write(0x80);          // the suggested ratio 0x80
    i2c_write(0xA8);          // 0xA8 set multiplex
    i2c_write(63);            // set height
    i2c_write(0xD3);          // set display offset
    i2c_write(0x0);           // no offset
    i2c_write(64);            // line #0 setstartline
    i2c_write(0x8D);          // 0x8D // chargepump
    i2c_write(0x14);
    i2c_write(0x20);          // memory mode
    i2c_write(0x00);          // 0x0 act like ks0108
    i2c_write(161);           // segremap
    i2c_write(0xC8);          // comscandec
    i2c_write(0xDA);          // 0xDA set com pins
    i2c_write(0x12);
    i2c_write(0x81);          // 0x81 // set contract
    i2c_write(0xCF);
    i2c_write(0xD9);          // 0xd9 set pre-charge
    i2c_write(0xF1);
    i2c_write(0xDB);          // SSD1306_SETVCOMDETECT
    i2c_write(0x40);
    i2c_write(0xA4);          // 0xA4 // display all on resume
    i2c_write(0xA6);          // 0xA6 // normal display
    i2c_write(0x2E);          // deactivate scroll
    i2c_write(0xAF);          // --turn on oled panel

    i2c_stop();
}

void drawPixel()
{
    i2c_start( SSD1306_ADDRESS );

    i2c_write(0x21);          // column address
    i2c_write(0);             // Column start address (0 = reset)
    i2c_write(127);           // Column end address (127
    i2c_write(0x22);          // page address
    i2c_write(0x00);          // Page start address (0 = reset)
    i2c_write(7);             // Page end address

    int i;

    int z=0;

    for ( i = 0; i < ( 128 * 64 / 8 ); i++ )
    {
        if ( z == 0 )
        {
            i2c_write( 0xff );
            z = 1;
        }
        else
        {
            i2c_write( 0x00 );
            z = 0;
        }
    }

    i2c_stop();
}

int main(void){

    i2c_init();
    initDisplay();
    drawPixel();

    return 0;
}

-ATMEGA328P connected to a 4.0v power source
-ADC5 (SCL) connected to OLED's SCL (with additional line to VCC with 15k resistor in between)
-ADC4 (SDA) connected to OLED's SDA (with additional line to VCC with 15k resistor in between)