Programming Processs

First we have to include the necessary libraries from the Arduino IDE

#include <WiFi.h>

This includes the WiFi library necessary for ESP32 to connect to a wireless network.

#include <Wire.h>

This includes the I2C communication library, which is used for interfacing with the OLED display.

#include <Adafruit_GFX.h>

This is the core graphics library from Adafruit used for drawing text, shapes, and images on displays.

#include <Adafruit_SSD1306.h>

This library is specifically for the SSD1306-based OLED displays to control how content is displayed.

#include <time.h>

This includes time-related functions, especially for syncing and formatting time from the internet using NTP (Network Time Protocol).

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Defines the width and height of the OLED display in pixels.

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

Initializes the OLED display object with defined width, height, I2C communication using Wire, and no reset pin (-1).

const char* ssid = "Muhesh";
const char* password = "876543219";

Stores the WiFi network name (SSID) and password as constant character pointers.

int currentScreen = 0;
unsigned long lastSlideTime = 0;
const int slideInterval = 3000;

Variables used to manage screen transitions: the current screen index, the last time the screen changed, and the slide interval (3 seconds).

void connectToWiFi()

This function attempts to connect the ESP32 to the specified WiFi network.

WiFi.begin(ssid, password);

Starts the WiFi connection using the given SSID and password.

while (WiFi.status() != WL_CONNECTED && retry < 40)

Retries the connection 40 times with a 500ms delay between each attempt.

void setupTime()

This function sets up internet time using NTP servers with GMT offset for IST (19800 seconds).

configTime(19800, 0, "pool.ntp.org", "time.nist.gov");

Configures the ESP32 to get the time from internet time servers with Indian Standard Time offset.

void setup()

This is the main setup function which runs once. It initializes the serial monitor, OLED display, WiFi connection, and time sync.

Serial.begin(115200);

Begins serial communication at 115200 baud rate for debugging purposes.

if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C))

Initializes the OLED screen with I2C address 0x3C. If it fails, it prints an error message and enters an infinite loop.

display.clearDisplay();
display.display();

Clears the OLED screen and refreshes it to make it blank initially.

String getTimeString()

Fetches the current time from the ESP32's internal clock and formats it as HH:MM:SS.

String getDateString()

Returns the current date in DD-MM-YYYY format.

String getDayString()

Returns the current day of the week (e.g., Monday, Tuesday).

void drawIndicators(int activeIndex)

Draws three indicator dots at the bottom of the screen to show which screen (time, date, or day) is currently active. The active screen dot is drawn larger.

void loop()

This is the main loop function that runs continuously. It updates the OLED screen every 3 seconds to show either the time, date, or day.

if (currentMillis - lastSlideTime >= slideInterval)

Checks if 3 seconds have passed since the last screen change to proceed with the next screen.

switch (currentScreen)

Determines which data (time, date, or day) to display based on the current screen index.

display.setTextSize(2);

Sets the size of the text to be drawn on the OLED screen.

display.setCursor((SCREEN_WIDTH - (textToShow.length() * 12)) / 2, yPos);

Calculates the horizontal position to center the text on the screen and sets the cursor position accordingly.

display.print(textToShow);

Displays the selected string (time, date, or day) on the OLED screen.

drawIndicators(currentScreen);

Displays the current screen indicator dots to indicate the active screen visually.

currentScreen = (currentScreen + 1) % 3;

Cycles the screen index between 0, 1, and 2 repeatedly to rotate through time, date, and day.

Complete Code

        #include <WiFi.h>
        #include <Wire.h>
        #include <Adafruit_GFX.h>
        #include <Adafruit_SSD1306.h>
        #include <time.h>

        #define SCREEN_WIDTH 128
        #define SCREEN_HEIGHT 64
        Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

        const char* ssid = "Muhesh";
        const char* password = "876543219";

        int currentScreen = 0;
        unsigned long lastSlideTime = 0;
        const int slideInterval = 3000;

        void connectToWiFi() {
        Serial.print("Connecting to WiFi");
        WiFi.begin(ssid, password);
        int retry = 0;
        while (WiFi.status() != WL_CONNECTED && retry < 40) {
            delay(500);
            Serial.print(".");
            retry++;
        }
        if (WiFi.status() == WL_CONNECTED) {
            Serial.println("\nWiFi connected");
            Serial.print("IP: ");
            Serial.println(WiFi.localIP());
        } else {
            Serial.println("\nFailed to connect WiFi");
        }
        }

        void setupTime() {
        configTime(19800, 0, "pool.ntp.org", "time.nist.gov");
        struct tm timeinfo;
        if (!getLocalTime(&timeinfo)) {
            Serial.println("Failed to get time");
        } else {
            Serial.println("Time synced");
        }
        }

        void setup() {
        Serial.begin(115200);

        if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
            Serial.println("OLED init failed");
            while (true);
        }
        display.clearDisplay();
        display.display();

        connectToWiFi();
        setupTime();
        }

        String getTimeString() {
        struct tm timeinfo;
        if (!getLocalTime(&timeinfo)) return "No Time";
        char buf[10];
        strftime(buf, sizeof(buf), "%H:%M:%S", &timeinfo);
        return String(buf);
        }

        String getDateString() {
        struct tm timeinfo;
        if (!getLocalTime(&timeinfo)) return "No Date";
        char buf[12];
        strftime(buf, sizeof(buf), "%d-%m-%Y", &timeinfo);
        return String(buf);
        }

        String getDayString() {
        struct tm timeinfo;
        if (!getLocalTime(&timeinfo)) return "No Day";
        char buf[12];
        strftime(buf, sizeof(buf), "%A", &timeinfo);
        return String(buf);
        }

        void drawIndicators(int activeIndex) {
        int dotY = SCREEN_HEIGHT - 10;
        int startX = (SCREEN_WIDTH - (3 * 16)) / 2;

        for (int i = 0; i < 3; i++) {
            if (i == activeIndex) {
            display.fillCircle(startX + i * 16, dotY, 5, SSD1306_WHITE);
            } else {
            display.fillCircle(startX + i * 16, dotY, 2, SSD1306_WHITE);
            }
        }
        }

        void loop() {
        unsigned long currentMillis = millis();

        if (currentMillis - lastSlideTime >= slideInterval) {
            lastSlideTime = currentMillis;

            String textToShow;
            switch (currentScreen) {
            case 0: textToShow = getTimeString(); break;
            case 1: textToShow = getDateString(); break;
            case 2: textToShow = getDayString(); break;
            }

            display.clearDisplay();
            display.setTextSize(2);
            display.setTextColor(SSD1306_WHITE);
            int yPos = (SCREEN_HEIGHT - 16) / 2;
            display.setCursor((SCREEN_WIDTH - (textToShow.length() * 12)) / 2, yPos);
            display.print(textToShow);

            drawIndicators(currentScreen);

            display.display();

            currentScreen = (currentScreen + 1) % 3;
        }
        }