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

#define TRIG_PIN 5
#define ECHO_PIN 18
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

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

const int tankHeight = 100; // Change this value based on your tank's height in cm

void setup() {
    Serial.begin(115200);
    pinMode(TRIG_PIN, OUTPUT);
    pinMode(ECHO_PIN, INPUT);

    if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
        Serial.println(F("SSD1306 allocation failed"));
        for (;;);
    }
    display.clearDisplay();
}

void loop() {
    long duration;
    float distance, waterLevel;

    // Trigger Ultrasonic Sensor
    digitalWrite(TRIG_PIN, LOW);
    delayMicroseconds(2);
    digitalWrite(TRIG_PIN, HIGH);
    delayMicroseconds(10);
    digitalWrite(TRIG_PIN, LOW);

    // Measure Echo Time
    duration = pulseIn(ECHO_PIN, HIGH);
    distance = (duration * 0.0343) / 2; // Convert time to distance (cm)

    // Calculate Water Level
    waterLevel = tankHeight - distance; // Assuming sensor is at top

    if (waterLevel < 0) waterLevel = 0;
    if (waterLevel > tankHeight) waterLevel = tankHeight;

    // Display on OLED
    display.clearDisplay();
    display.setTextSize(2);
    display.setTextColor(WHITE);
    display.setCursor(0, 0);
    display.print("Water Level:");
    display.setCursor(0, 30);
    display.print(waterLevel);
    display.print(" cm");
    display.display();

    Serial.print("Water Level: ");
    Serial.print(waterLevel);
    Serial.println(" cm");

    delay(1000);
}