# Sensor Monitor rev_02

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    - Project: # Sensor Monitor
    - Version: 002
    - Source Code NOT compiled for: ESP32 DevKit V1
    - Source Code created on: 2026-03-15 00:36:34

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/****** SYSTEM REQUIREMENTS *****/
/****** SYSTEM REQUIREMENT 1 *****/
    /* Read temperature and humidity from DHT22 sensor on */
    /* GPIO4. Display real-time readings on SSD1306 OLED */
    /* with updates every 2 seconds. Show "Temp: XX.X°C" */
    /* and "Humidity: XX.X%" on separate lines */
/****** END SYSTEM REQUIREMENTS *****/


/* START CODE */

/****** SYSTEM REQUIREMENTS *****/
// System Requirement 1: "Read temperature and humidity from DHT22 sensor on GPIO4. Display real-time readings on SSD1306 OLED with updates every 2 seconds. Show "Temp: XX.X°C" and "Humidity: XX.X%" on separate lines"

/****** DEFINITION OF LIBRARIES *****/
#include <Wire.h>
#include <Adafruit_SSD1306.h>
#include <U8g2_for_Adafruit_GFX.h>
#include <Adafruit_GFX.h>
#include <DHT.h>

/****** FUNCTION PROTOTYPES *****/
void setup(void);
void loop(void);
void initializeDisplay(void);
void initializeDHT22(void);
void readDHT22Sensor(void);
void displaySensorData(void);
void updateDisplay(void);

/***** DEFINITION OF I2C PINS *****/
const uint8_t myDisplay_SSD1306OledDisplay_I2C_PIN_SDA_D21 = 21;
const uint8_t myDisplay_SSD1306OledDisplay_I2C_PIN_SCL_D22 = 22;
const uint8_t myDisplay_SSD1306OledDisplay_I2C_SLAVE_ADDRESS = 0x3C;

/***** DEFINITION OF DHT22 SENSOR PINS *****/
const uint8_t DHT22_SENSOR_PIN = 4;
const uint8_t DHT_SENSOR_TYPE = DHT22;

/***** DEFINITION OF DISPLAY PARAMETERS *****/
const int SCREEN_WIDTH = 128;
const int SCREEN_HEIGHT = 64;
const int OLED_RESET = -1;

/****** DEFINITION OF LIBRARIES CLASS INSTANCES*****/
// Adafruit_SSD1306 display constructor: width, height, I2C address, reset pin
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// U8g2 font engine for advanced text rendering
U8G2_FOR_ADAFRUIT_GFX u8g2_for_adafruit_gfx;

// DHT22 sensor instance
DHT dht22Sensor(DHT22_SENSOR_PIN, DHT_SENSOR_TYPE);

/***** DEFINITION OF TIMING VARIABLES *****/
unsigned long lastDisplayUpdate = 0;
const unsigned long DISPLAY_UPDATE_INTERVAL = 2000;

/***** DEFINITION OF SENSOR DATA VARIABLES *****/
float sensorTemperature = 0.0;
float sensorHumidity = 0.0;
boolean sensorReady = false;
unsigned long dhtReadCounter = 0;

/****** setup() - SYSTEM INITIALIZATION *****/
void setup(void)
{
    // Initialize Serial communication for debugging
    Serial.begin(115200);
    delay(500);
    Serial.println("\n\nStarting ESP32 DHT22 and SSD1306 OLED Display Initialization...");

    // Initialize the I2C bus with specified pins
    Wire.begin(myDisplay_SSD1306OledDisplay_I2C_PIN_SDA_D21,
               myDisplay_SSD1306OledDisplay_I2C_PIN_SCL_D22);
    Serial.println("I2C bus initialized successfully");

    // Initialize the OLED display
    initializeDisplay();

    // Initialize DHT22 sensor
    initializeDHT22();

    // Initialize the update timer
    lastDisplayUpdate = millis();

    Serial.println("Setup completed successfully");
}

/****** loop() - MAIN EXECUTION LOOP *****/
void loop(void)
{
    // Read DHT22 sensor every 2 seconds
    if (millis() - lastDisplayUpdate >= DISPLAY_UPDATE_INTERVAL)
    {
        // Read sensor values from DHT22
        readDHT22Sensor();

        // Update display with real-time sensor readings
        updateDisplay();

        // Update the display timer
        lastDisplayUpdate = millis();
    }

    // Small delay to prevent watchdog timeout
    delay(100);
}

/****** initializeDisplay() - INITIALIZE SSD1306 OLED DISPLAY VIA I2C *****/
void initializeDisplay(void)
{
    // Initialize display with I2C address 0x3C
    if (!display.begin(SSD1306_SWITCHCAPVCC, myDisplay_SSD1306OledDisplay_I2C_SLAVE_ADDRESS))
    {
        Serial.println(F("SSD1306 allocation failed"));
        // Halt execution if display initialization fails
        for (;;)
        {
            delay(100);
        }
    }

    Serial.println("SSD1306 OLED display initialized successfully");

    // Connect U8g2 font engine to Adafruit GFX display
    u8g2_for_adafruit_gfx.begin(display);

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

    Serial.println("Display ready for content");
}

/****** initializeDHT22() - INITIALIZE DHT22 TEMPERATURE AND HUMIDITY SENSOR *****/
void initializeDHT22(void)
{
    // Configure GPIO4 as input for DHT22 data line
    pinMode(DHT22_SENSOR_PIN, INPUT_PULLUP);

    // Initialize DHT22 sensor
    dht22Sensor.begin();

    Serial.println("DHT22 sensor initialized successfully on GPIO4");

    // Delay to allow DHT22 to stabilize
    delay(2000);

    // Perform initial sensor read
    readDHT22Sensor();

    Serial.println("DHT22 sensor ready for readings");
}

/****** readDHT22Sensor() - READ TEMPERATURE AND HUMIDITY FROM DHT22 SENSOR *****/
void readDHT22Sensor(void)
{
    // Read humidity value from DHT22
    float humidity = dht22Sensor.readHumidity();

    // Read temperature value from DHT22 in Celsius
    float temperature = dht22Sensor.readTemperature();

    // Check if any reads failed and exit early (to try again)
    if (isnan(humidity) || isnan(temperature))
    {
        Serial.println("Failed to read from DHT22 sensor!");
        sensorReady = false;
        return;
    }

    // Update global sensor variables with fresh readings
    sensorTemperature = temperature;
    sensorHumidity = humidity;
    sensorReady = true;
    dhtReadCounter++;

    // Debug output with sensor readings
    Serial.print("DHT22 Read #");
    Serial.print(dhtReadCounter);
    Serial.print(" - Temperature: ");
    Serial.print(sensorTemperature, 1);
    Serial.print("°C, Humidity: ");
    Serial.print(sensorHumidity, 1);
    Serial.println("%");
}

/****** displaySensorData() - DISPLAY REAL-TIME SENSOR DATA WITH TEXT FORMATTING *****/
void displaySensorData(void)
{
    // Set font mode for U8g2 (transparent mode)
    u8g2_for_adafruit_gfx.setFontMode(1);

    // Set font direction (left to right)
    u8g2_for_adafruit_gfx.setFontDirection(0);

    // Set foreground color (white text)
    u8g2_for_adafruit_gfx.setForegroundColor(SSD1306_WHITE);

    // Display header with larger font
    u8g2_for_adafruit_gfx.setFont(u8g2_font_helvB14_tf);
    u8g2_for_adafruit_gfx.setCursor(0, 18);
    u8g2_for_adafruit_gfx.print(F("DHT22 DATA"));

    // Check if sensor is ready and display status
    if (!sensorReady)
    {
        u8g2_for_adafruit_gfx.setFont(u8g2_font_helvR10_tf);
        u8g2_for_adafruit_gfx.setCursor(0, 35);
        u8g2_for_adafruit_gfx.print(F("Sensor Error"));
        return;
    }

    // Display temperature with formatted text
    u8g2_for_adafruit_gfx.setFont(u8g2_font_helvR12_tf);
    u8g2_for_adafruit_gfx.setCursor(0, 35);
    u8g2_for_adafruit_gfx.print(F("Temp: "));
    u8g2_for_adafruit_gfx.print(sensorTemperature, 1);
    u8g2_for_adafruit_gfx.print(F("\xb0C"));

    // Display humidity with formatted text
    u8g2_for_adafruit_gfx.setCursor(0, 50);
    u8g2_for_adafruit_gfx.print(F("Humidity: "));
    u8g2_for_adafruit_gfx.print(sensorHumidity, 1);
    u8g2_for_adafruit_gfx.print(F("%"));

    // Display read count
    u8g2_for_adafruit_gfx.setFont(u8g2_font_helvR08_tf);
    u8g2_for_adafruit_gfx.setCursor(0, 62);
    u8g2_for_adafruit_gfx.print(F("Reads: "));
    u8g2_for_adafruit_gfx.print(dhtReadCounter);
}

/****** updateDisplay() - UPDATE DISPLAY WITH REAL-TIME SENSOR DATA EVERY 2 SECONDS *****/
void updateDisplay(void)
{
    // Clear the display buffer to erase previous content
    display.clearDisplay();

    // Display sensor data with formatted text
    displaySensorData();

    // Push the display buffer to the physical display
    display.display();

    // Debug output to Serial
    Serial.print("Display updated with sensor data - Temp: ");
    Serial.print(sensorTemperature, 1);
    Serial.print("°C, Humidity: ");
    Serial.print(sensorHumidity, 1);
    Serial.println("%");
}

/* END CODE */