# OLED Display rev_02

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    - Project: OLED_DISPLAY
    - Version: 002
    - Source Code compiled for: ESP32 DevKit V1
    - Source Code created on: 2026-03-07 04:58:59

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/****** SYSTEM REQUIREMENTS *****/
/****** SYSTEM REQUIREMENT 1 *****/
    /* Display "Hello World" on OLED at startup, then */
    /* increment a counter every second and display it on */
    /* the screen */
/****** END SYSTEM REQUIREMENTS *****/



/* START CODE */

/****** DEFINITION OF LIBRARIES *****/
#include <Wire.h>
#include <Adafruit_SSD1306.h>   //https://github.com/stblassitude/Adafruit_SSD1306_Wemos_OLED.git
#include <U8g2_for_Adafruit_GFX.h>  //https://github.com/olikraus/U8g2_for_Adafruit_GFX
#include <Adafruit_SSD1306.h>   //https://github.com/adafruit/Adafruit_SSD1306
#include <Adafruit_GFX.h>   //https://github.com/adafruit/Adafruit-GFX-Library

/****** FUNCTION PROTOTYPES *****/
void setup(void);
void loop(void);

/***** DEFINITION OF I2C PINS *****/
const uint8_t OledDisplay_SSD1306OledDisplay_I2C_PIN_SDA_D21        = 21;
const uint8_t OledDisplay_SSD1306OledDisplay_I2C_PIN_SCL_D22        = 22;
const uint8_t OledDisplay_SSD1306OledDisplay_I2C_SLAVE_ADDRESS      = 60;

/****** DEFINITION OF OLED DISPLAY CONSTANTS *****/
#define SCREEN_WIDTH 128        // OLED display width in pixels
#define SCREEN_HEIGHT 64        // OLED display height in pixels
#define OLED_RESET -1           // Reset pin (not used, set to -1)

/****** DEFINITION OF LIBRARIES CLASS INSTANCES*****/
// Create Adafruit SSD1306 display object using I2C
// The address is 0x3C (60 in decimal) as specified in the constant
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Create U8g2_for_Adafruit_GFX object for enhanced font rendering
U8G2_FOR_ADAFRUIT_GFX u8g2_for_adafruit_gfx;

/****** GLOBAL VARIABLES *****/
unsigned long lastUpdateTime = 0;  // Stores the last time counter was updated
uint32_t counter = 0;               // Counter that increments every second

void setup(void)
{
    // Initialize Serial communication for debugging
    Serial.begin(115200);
    delay(100);
    Serial.println("\n\nESP32 OLED Display Test Starting...");

    // Initialize I2C communication with custom pins
    Wire.begin(OledDisplay_SSD1306OledDisplay_I2C_PIN_SDA_D21,
               OledDisplay_SSD1306OledDisplay_I2C_PIN_SCL_D22);
    delay(100);

    // Initialize the OLED display with the I2C address 0x3C
    if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
        Serial.println(F("SSD1306 allocation failed"));
        // Hang in an infinite loop if display fails to initialize
        while (1) {
            delay(1000);
        }
    }

    // Clear the display buffer
    display.clearDisplay();

    // Initialize U8g2 font rendering
    u8g2_for_adafruit_gfx.begin(display);

    // Display "Hello World" at startup
    display.clearDisplay();
    display.setTextSize(1);
    display.setTextColor(SSD1306_WHITE);
    display.setCursor(0, 0);
    display.println(F("Hello World"));
    display.display();

    // Initialize the last update time
    lastUpdateTime = millis();

    Serial.println("Setup complete. Display initialized.");
}

void loop(void)
{
    // Get the current time in milliseconds
    unsigned long currentTime = millis();

    // Check if one second (1000 milliseconds) has passed since the last update
    if (currentTime - lastUpdateTime >= 1000) {
        // Update the last update time
        lastUpdateTime = currentTime;

        // Increment the counter
        counter++;

        // Clear the display buffer
        display.clearDisplay();

        // Display "Hello World" on the first line
        display.setTextSize(1);
        display.setTextColor(SSD1306_WHITE);
        display.setCursor(0, 0);
        display.println(F("Hello World"));

        // Display the counter value on the second line
        display.setCursor(0, 16);
        display.print(F("Counter: "));
        display.println(counter);

        // Update the display
        display.display();

        // Print counter value to Serial for debugging
        Serial.print("Counter: ");
        Serial.println(counter);
    }

    // Small delay to prevent overwhelming the processor
    delay(10);
}

/* END CODE */