Email Monitor IoT Application - Carenuity Level 3 Challenge

Project Overview

This project is a submission for the Carenuity Level 3 Challenge: API Usage & App Development. It demonstrates practical API integration, IoT development, and power management in an Arduino-based application that monitors important emails and displays them on a real-time OLED screen.

Challenge Context

The Carenuity Level 3 challenge focuses on:

• Creating custom applications using the Arduino IDE
• Integrating third-party APIs into IoT projects
• Leveraging AI assistance (ChatGPT) for code optimization
• Uploading and sharing projects on the Solution Builder platform
• Building practical IoT solutions that solve real-world problems

Project Description

This Email Monitor application transforms an ESP32-S2 Mini microcontroller into an intelligent email notification device. It connects to the internet, fetches important email metadata via a Google Apps Script API, and displays the information on an OLED screen—all while optimizing power consumption through deep sleep cycles.

Key Features

✅ WiFi Connectivity - Connects to home/office network for internet access
✅ Google Apps Script Integration - Fetches email data via custom API endpoint
✅ OLED Display - Shows email count and latest subject on 128x64 display
✅ Power Management - Uses deep sleep (~5-minute intervals) for extended battery operation
✅ Real-time Updates - Automatically polls for new important emails
✅ Trim & Parse - Cleans and formats incoming data for reliable display

Hardware Components

Component	Details
Microcontroller	ESP32-S2 Mini
Display	Adafruit SSD1306 OLED (128x64, I2C)
Communication	WiFi (built-in) & I2C (display connection)
Pins Used	SDA: GPIO 33, SCL: GPIO 35
Power	USB or Battery (deep sleep optimized)

Technical Architecture

System Components

┌─────────────────────┐
│   ESP32-S2 Mini     │
│  (Microcontroller)  │
└──────────┬──────────┘
           │
     ┌─────┴─────┐
     │           │
     ▼           ▼
  [WiFi]    [I2C Bus]
     │           │
     │           ▼
     │    ┌────────────────┐
     │    │ SSD1306 OLED   │
     │    │ Display 128x64 │
     │    └────────────────┘
     │
     ▼
 [Google Apps Script API]
     │
     ▼
 [Gmail / Email Service]

Application Flow

1. Initialization Phase

   • ESP32 boots and initializes I2C communication
   • OLED display activates and displays connection status
   • Device attempts WiFi connection

2. Connected State

   • Displays "WiFi Online!" confirmation

3. Main Loop - Data Fetching

   • Makes HTTP GET request to Google Apps Script
   • Receives payload: count|subject
   • Parses data and updates display

4. Display Update

   • Shows: "IMPORTANT EMAILS:" header
   • Shows: Email count
   • Shows: "LATEST SUBJECT:" header
   • Shows: Most recent email subject

5. Power Management

   • Logs "Going to sleep for 5 minutes..."
   • Enables deep sleep timer (5 × 60 × 1,000,000 microseconds)
   • Enters ESP deep sleep mode
   • Wakes automatically, repeats from Main Loop

Code Breakdown

Network Configuration

const char* ssid = "Barbara";           // WiFi SSID
const char* password = "Cleopatra123";  // WiFi Password
const char* scriptUrl = "...";          // Google Apps Script endpoint

Display Initialization

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);
// Custom I2C pins for ESP32-S2 Mini
Wire.begin(33, 35);  // SDA=33, SCL=35

HTTP Request & Response Parsing

// Fetches data from Google Apps Script
http.begin(scriptUrl);
int httpCode = http.GET();
String payload = http.getString();
// Parses format: "count|subject"
int splitIndex = payload.indexOf('|');
String count = payload.substring(0, splitIndex);
String subject = payload.substring(splitIndex + 1);

Deep Sleep Implementation

// Converts 5 minutes to microseconds
uint64_t sleepTime = 5 * 60 * 1000000;
esp_sleep_enable_timer_wakeup(sleepTime);
esp_deep_sleep_start();  // The "Magic" Level 3 command

Display Functions

• showStatus(String msg) - Shows large status messages (WiFi connection, errors)
• updateDisplay(String count, String subject) - Displays formatted email information

Setup & Installation

Prerequisites

• Arduino IDE installed
• ESP32 board support added to Arduino IDE
• Required libraries:
  • WiFi.h (built-in with ESP32)
  • HTTPClient.h (built-in with ESP32)
  • Wire.h (built-in with ESP32)
  • Adafruit_GFX.h
  • Adafruit_SSD1306.h

Steps

1. Install Dependencies

   • In Arduino IDE: Sketch → Include Library → Manage Libraries
   • Search and install: "Adafruit GFX" and "Adafruit SSD1306"

2. Configure WiFi Credentials

   const char* ssid = "Your_Network_SSID";
   const char* password = "Your_Network_Password";

3. Set Google Apps Script URL

   • Create a Google Apps Script that monitors Gmail
   • Deploy as web app with appropriate permissions
   • Update scriptUrl with your endpoint

4. Board Selection

   • Tools → Board → ESP32S2 (or your specific variant)
   • Tools → Port → Select your ESP32 port

5. Upload

   • Sketch → Upload
   • Open Serial Monitor (115200 baud) to verify connection

Google Apps Script Integration

The backend uses Google Apps Script to:

• Access Gmail API
• Filter for important emails/labels
• Return data in format: count|subject
• Handle authentication and caching

Example response structure:

5|Re: Urgent Project Update - Q1 2025

Power Consumption Optimization

This project uses ESP32 Deep Sleep for power efficiency:

• Active Time: ~3-5 seconds (WiFi + HTTP + Display)
• Sleep Time: 5 minutes (uses minimal power)
• Deep Sleep Current: ~10-100 µA (compared to ~80 mA active)

Result: Approximately 96-98% power reduction compared to continuous operation!

Expected Behavior

Serial Output Example

...
Going to sleep for 5 minutes...

Display States

State 1 - Connecting:

Connecting WiFi...

State 2 - Connected:

WiFi Online!

State 3 - Email Data:

IMPORTANT EMAILS:
> 5

LATEST SUBJECT:
Team Meeting Notes - March

Troubleshooting

Issue	Solution
Display not showing	Verify I2C address (0x3C), check SDA/SCL pin connections
WiFi won't connect	Check SSID/password, verify network compatibility (2.4GHz)
HTTP Error messages	Verify Google Apps Script URL is correct and deployed
No data displayed	Check Google Apps Script returns correct format (count|subject)
Frequent reboots	May indicate power issues or memory problems

Learning Outcomes (Carenuity Level 3)

Technical Competencies Gained

✓ Real-world API integration and HTTP communication
✓ IoT device programming with microcontrollers
✓ I2C display communication protocols
✓ Power management and deep sleep optimization
✓ WiFi connectivity and network debugging

Soft Skills Developed

✓ Problem-solving through API debugging
✓ Time management in multi-component projects
✓ Technical documentation and communication
✓ Community engagement through project sharing

Future Enhancements

• Add multiple email labels/filters
• Display email sender information
• Button control for manual refresh or configuration
• Battery level indicator
• Multiple OLED screens for more data
• Mobile app integration
• Cloud logging of email trends

References & Resources

• Carenuity Challenge: https://carenuity.com/home-challenge/level-3/
• ESP32-S2 Mini Documentation: https://www.espressif.com/
• Adafruit SSD1306 Library: https://github.com/adafruit/Adafruit_SSD1306
• Google Apps Script Guide: https://developers.google.com/apps-script
• Arduino IDE: https://www.arduino.cc/en/software

Repository Structure

Carenuity_project/
├── code.cpp          # Main Arduino sketch
├── README.md         # This file
└── binary/           # Compiled binary (for Solution Builder)

Submission Information

Challenge Level: 3 - API Usage & App Development
Platform: Solution Builder (https://solutions.carenuity.com)
Reward: DS18B20 Sensor / Oximeter Sensor
Difficulty: Basic
Tutor: Paul

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Status: ✅ Completed and Ready for Submission

For questions or to share this project, contact: team@carenuity.com