Smart Environment Monitor

TIMEEstimated Time

LEVELDifficulty

PREPrerequisites

• Reading Environmental Sensors You should already be able to read BME280 temperature, humidity, and pressure values.
• I2C Communication You should understand why the OLED and BME280 share SDA and SCL.
• Button Debouncing You will use a button to switch display pages reliably.

SKILLSkills You'll Learn

• Combine sensor input, OLED output, LEDs, and a button in one project
• Use thresholds to turn measurements into system status
• Switch OLED display pages with a debounced button
• Sample environmental data at a stable interval
• Build and test a small real-world embedded monitoring system

PARTSComponents Required

• ESP32ESP32 DevKit V1Runs the complete monitor logic
• BMEBME280 environmental sensorMeasures temperature, humidity, and pressure
• OLEDSSD1306 OLED displayShows monitor pages and status
• LEDGreen LED and red LEDShow normal and warning status
• BTNPush buttonSwitches between OLED pages
• WIREBreadboard, jumper wires, and LED resistorsBuild the complete circuit safely

ENGEngineering Explanation

REALReal-World Analogy

WIREWiring Diagram

Follow these steps in order. Unplug USB before you change any wires.

1. 1

   Unplug the ESP32 USB cable before wiring.

2. 2

   Connect BME280 VCC to ESP32 3.3 V and BME280 GND to ESP32 GND.

3. 3

   Connect BME280 SDA to GPIO21 and BME280 SCL to GPIO22.

4. 4

   Connect OLED VCC to ESP32 3.3 V and OLED GND to ESP32 GND.

5. 5

   Connect OLED SDA to the same GPIO21 SDA row and OLED SCL to the same GPIO22 SCL row.

6. 6

   Connect GPIO18 through a 220 ohm or 330 ohm resistor to the green LED anode, then connect the LED cathode to GND.

7. 7

   Connect GPIO19 through a 220 ohm or 330 ohm resistor to the red LED anode, then connect the LED cathode to GND.

8. 8

   Connect one side of the push button to GPIO23 and the other side to GND.

9. 9

   The button uses INPUT_PULLUP, so pressed reads LOW and released reads HIGH.

10. 10

    Install Adafruit BME280, Adafruit Unified Sensor, Adafruit SSD1306, and Adafruit GFX from Arduino Library Manager.

GPIOGPIO Table

⌨️Arduino Code

Copy this into Arduino IDE, then click Upload.

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Adafruit_BME280.h>

const int I2C_SDA = 21;
const int I2C_SCL = 22;

const int GREEN_LED_PIN = 18;
const int RED_LED_PIN = 19;
const int BUTTON_PIN = 23;

const int SCREEN_WIDTH = 128;
const int SCREEN_HEIGHT = 64;
const int OLED_RESET = -1;
const int OLED_ADDRESS = 0x3C;

const float TEMP_APPROACH_C = 28.0;
const float TEMP_WARNING_C = 30.0;

const unsigned long SAMPLE_INTERVAL_MS = 2000;
const unsigned long DEBOUNCE_MS = 40;

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
Adafruit_BME280 bme;

float temperatureC = 0.0;
float humidity = 0.0;
float pressureHpa = 0.0;

int currentPage = 0;
int lastButtonReading = HIGH;
int stableButtonState = HIGH;
unsigned long lastButtonChangeTime = 0;
unsigned long lastSampleTime = 0;

void setup() {
  Serial.begin(115200);
  delay(1000);

  pinMode(GREEN_LED_PIN, OUTPUT);
  pinMode(RED_LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);

  Wire.begin(I2C_SDA, I2C_SCL);

  if (!display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDRESS)) {
    Serial.println("OLED not found. Check wiring and address.");
    while (true) {
      delay(1000);
    }
  }

  bool bmeReady = bme.begin(0x76);
  if (!bmeReady) {
    bmeReady = bme.begin(0x77);
  }

  if (!bmeReady) {
    Serial.println("BME280 not found at 0x76 or 0x77.");
    showMessage("BME280 not found", "Check I2C wiring");
    while (true) {
      delay(1000);
    }
  }

  showMessage("Course 01", "Capstone ready");
  Serial.println("Mission 12: Smart Environment Monitor ready");
  delay(1500);
}

void loop() {
  handleButton();

  unsigned long now = millis();
  if (now - lastSampleTime >= SAMPLE_INTERVAL_MS) {
    lastSampleTime = now;
    readSensorData();
    updateAlerts();
    printSerialReport();
    updateDisplay();
  }
}

void handleButton() {
  int reading = digitalRead(BUTTON_PIN);

  if (reading != lastButtonReading) {
    lastButtonChangeTime = millis();
    lastButtonReading = reading;
  }

  if ((millis() - lastButtonChangeTime) > DEBOUNCE_MS) {
    if (reading != stableButtonState) {
      stableButtonState = reading;

      if (stableButtonState == LOW) {
        currentPage = 1 - currentPage;
        updateDisplay();
      }
    }
  }
}

void readSensorData() {
  temperatureC = bme.readTemperature();
  humidity = bme.readHumidity();
  pressureHpa = bme.readPressure() / 100.0;
}

String environmentStatus() {
  if (temperatureC >= TEMP_WARNING_C) {
    return "WARNING";
  }

  if (temperatureC >= TEMP_APPROACH_C) {
    return "WARM";
  }

  return "NORMAL";
}

void updateAlerts() {
  String status = environmentStatus();

  digitalWrite(GREEN_LED_PIN, status == "NORMAL" ? HIGH : LOW);
  digitalWrite(RED_LED_PIN, status == "WARNING" ? HIGH : LOW);
}

void updateDisplay() {
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);

  if (currentPage == 0) {
    display.setCursor(0, 0);
    display.println("Page 1: Climate");
    display.setCursor(0, 20);
    display.print("Temp: ");
    display.print(temperatureC, 1);
    display.println(" C");
    display.setCursor(0, 38);
    display.print("Hum:  ");
    display.print(humidity, 1);
    display.println(" %");
  } else {
    display.setCursor(0, 0);
    display.println("Page 2: Status");
    display.setCursor(0, 20);
    display.print("Pres: ");
    display.print(pressureHpa, 1);
    display.println(" hPa");
    display.setCursor(0, 42);
    display.print("Status: ");
    display.println(environmentStatus());
  }

  display.display();
}

void printSerialReport() {
  Serial.print("Temperature: ");
  Serial.print(temperatureC, 1);
  Serial.print(" C | Humidity: ");
  Serial.print(humidity, 1);
  Serial.print(" % | Pressure: ");
  Serial.print(pressureHpa, 1);
  Serial.print(" hPa | Status: ");
  Serial.println(environmentStatus());
}

void showMessage(const char* line1, const char* line2) {
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(0, 14);
  display.println(line1);
  display.setCursor(0, 34);
  display.println(line2);
  display.display();
}

CODELine-by-line Explanation

• The include lines load the I2C, OLED, graphics, and BME280 libraries needed by the project.
• GPIO21 and GPIO22 are used for the shared I2C bus, matching the OLED and BME280 lessons.
• GPIO18 and GPIO19 control the green and red LED alert outputs.
• GPIO23 reads the page button with INPUT_PULLUP, so pressing the button connects the pin to GND and reads LOW.
• TEMP_APPROACH_C and TEMP_WARNING_C are the decision thresholds. They turn numbers into status.
• SAMPLE_INTERVAL_MS keeps sensor reading stable instead of reading as fast as possible.
• The button handler uses debounce timing so one physical press changes the page once.
• readSensorData() keeps measurement code separate from display and alert code.
• environmentStatus() is the decision-making function. It returns NORMAL, WARM, or WARNING.
• updateAlerts() turns the LEDs on or off based on the current status.
• updateDisplay() shows either Page 1 or Page 2 depending on the button-selected page.
• printSerialReport() prints complete formatted data for debugging and testing.

WARNCommon Mistakes

• Forgetting LED resistors

  The LEDs need current limiting even in a capstone project.

• Expecting yellow LED hardware

  The project uses yellow as an OLED status text, not a separate LED.

• Button switches pages many times

  Mechanical bounce creates repeated transitions.

• OLED and BME280 disappear together

  Shared I2C wiring means one bad SDA or SCL connection can affect both modules.

• Temperature warning never triggers

  The room may be below the warning threshold.

• Red LED stays on

  Threshold may be too low or the sensor is near heat.

• Display looks crowded

  Trying to show all values on one tiny OLED page is hard to read.

• Sampling too fast

  Fast sampling makes normal fluctuation look dramatic.

• No Serial Monitor output

  Wrong baud rate or upload problem.

• Treating this as only a wiring exercise

  The real lesson is system design.

!Troubleshooting

Most ESP32 problems are wiring, power, library, or timing issues. Check these first.

• Nothing appears on the OLED

  Likely cause: OLED address, power, or I2C wiring may be wrong.

  Fix: Run the I2C scanner from Mission 10 and confirm the OLED address.

• BME280 not found

  Likely cause: Sensor address or wiring is wrong.

  Fix: Check for 0x76 or 0x77 with the scanner, then confirm 3.3 V, GND, SDA, and SCL.

• Button does nothing

  Likely cause: The button may not connect GPIO23 to GND when pressed.

  Fix: Check the button orientation and confirm INPUT_PULLUP wiring.

• LEDs are backwards

  Likely cause: LED polarity is reversed.

  Fix: Connect the longer leg through the resistor to the GPIO side and the shorter leg to GND.

• Values look unrealistic

  Likely cause: Sensor placement, heat, address mismatch, or wrong module can affect readings.

  Fix: Move the sensor away from heat and compare with Mission 11 output.

TIPEngineer Tip

REMRemember This Forever

?FAQs

• Why is this mission called a capstone?

  A capstone combines many earlier skills into one complete project. This monitor uses GPIO, buttons, debouncing, I2C, OLED display, sensor readings, thresholds, and debugging.

• Why does the monitor need thresholds?

  Thresholds turn raw measurements into decisions. The ESP32 does not just read temperature; it decides whether the environment is normal or needs attention.

• Why use two OLED pages?

  A small OLED cannot show everything clearly at once. Pages make the display easier to read, just like menus in real devices.

• Why use a button if the OLED can update automatically?

  The button gives the user control. It also lets you practice reliable input handling in a complete project.

• Why does the Serial Monitor still matter?

  Serial Monitor is the engineering view. The OLED is the user view. Real projects often keep both during development.

• Why not read the BME280 as fast as possible?

  Room conditions change slowly. Fast reading wastes effort and can make normal noise look more important than it is.

• Can I use a DHT22 instead of BME280?

  You can build a simpler version with DHT22 for temperature and humidity, but this capstone uses BME280 because it also measures pressure and uses I2C.

• Why are the LEDs useful if the OLED already shows status?

  LEDs provide instant glanceable feedback. A user can see normal or warning status without reading the screen.

• What should I put on GitHub for this project?

  Include the Arduino sketch, wiring notes, a short README, threshold values, photos of your build, and what you tested.

• What should I learn after Course 01?

  Move into connected IoT: WiFi, HTTP, REST APIs, MQTT, JSON, dashboards, Firebase, OTA updates, Bluetooth, and real IoT projects.