Weather Data Center – ESP8266

Embedded weather monitoring firmware running on ESP8266 using a Finite State Machine and Event-Driven architecture.

The firmware is built with Arduino CLI and designed to be modular and extensible for IoT applications.

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Architecture

The system follows a State Machine + Event Bus architecture.

The State Machine controls application flow, while services communicate through an event dispatcher.

This ensures:

• loose coupling
• modular services
• non-blocking firmware
• easy feature expansion

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Architecture Diagram

flowchart TD

    A[App State Machine] --> B[DHT Sensor Service] --> C[Event Bus]

    C --> D[OLED Display Service]
    C --> E[ESPNow Wireless Service]
    C --> F[Logger Service]

    E --> G[Remote ESP8266 Node]

    style A fill:#66514E
    style C fill:#e6f7ff

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Components

Component	Responsibility
App FSM	Controls firmware lifecycle
DHTService	Reads temperature and humidity
Event Bus	Dispatches sensor events
OLEDService	Displays readings
ESPNowService	Sends readings wirelessly
Logger	Serial debugging

Wireless communication uses ESP-NOW.

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Application State Machine

The application logic runs inside a Finite State Machine (FSM).

States

State	Description
INIT	Initialize services
IDLE	Wait for next reading
READ_SENSOR	Acquire sensor data
ERROR	Error handling

State Flow

stateDiagram-v2
    [*] --> INIT
    INIT --> APP_CONNECT: Address isExist 
    INIT --> APP_SCAN : Address notFound
    APP_SCAN --> APP_CONNECT
    APP_CONNECT -->APP_IDLE
    
    APP_IDLE --> APP_SCAN:  button hold pressed 
    APP_IDLE --> APP_READ_SENSOR : lastTrigger > 2s
    APP_READ_SENSOR --> APP_IDLE
    

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The loop is non-blocking and relies on millis() timers.

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ESP-NOW Flow Sequence

The system uses a publish / subscribe model.

When sensor data is available, it is broadcast to all services.

sequenceDiagram

    participant App
    participant ESPNowService
    participant EEPROMStorage
    App->>EEPROMStorage: loading address
    EEPROMStorage-->App: 
    alt Address found
    App->>ESPNowService: Start Esp-Now
    else  Adress found
    App->>+ESPNowService:WIFI Scaning 
    ESPNowService-->ESPNowService:Scan Network
    ESPNowService->>-App: is connected
    ESPNowService-->App: get Mac Address
    App->>EEPROMStorage: save Mac Address
    App->>ESPNowService: Start Esp-Now
    end

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Event Flow Sequence

sequenceDiagram

    participant App
    participant DHTService
    participant EventBus
    participant OLED
    participant ESPNow
    participant Logger

    App->>DHTService: request sensor read
    DHTService->>EventBus: publish(temp, humidity)

    EventBus->>OLED: update display
    EventBus->>ESPNow: transmit data
    EventBus->>Logger: print debug

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Advantages:

• multiple consumers for one event
• services are independent
• easy to extend

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Project Structure

weather_Data_Center/
│
├── app/
│   ├── App.cpp
│   ├── Event.cpp
│   └── Logger.cpp
│
├── sensors/
│   └── DHTService.cpp
│
├── display/
│   └── OLEDService.cpp
│
├── wireless/
│   └── ESPNowService.cpp
│
└── weather_Data_Center.ino

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2. Subscribe to Events

Register the service in the application initialization.

Event::subscribe(MQTTService::onSensor);

Now the service automatically receives sensor updates.

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3. Initialize the Service

Add initialization inside App::init().

MQTTService::init();

Done. The new service now reacts to sensor events without modifying existing modules.

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Design Principles

The firmware follows key embedded design principles:

• Event-driven programming
• Finite State Machine control
• Non-blocking execution
• Modular services
• Hardware abstraction

This architecture allows future extensions such as:

• MQTT telemetry
• OTA firmware updates
• Web dashboard
• SD card logging
• multi-node sensor networks

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1. Install Arduino CLI

Linux / macOS

curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | sh

Move it to your PATH:

sudo mv bin/arduino-cli /usr/local/bin/

Windows

Download Arduino CLI from: https://arduino.github.io/arduino-cli/latest/installation/

Verify installation:

arduino-cli version

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2. Initialize Arduino CLI

Run:

arduino-cli config init

This creates the configuration file:

~/.arduino15/arduino-cli.yaml

Update the board manager URL for ESP8266.

Example configuration:

board_manager:
  additional_urls:
    - https://arduino.esp8266.com/stable/package_esp8266com_index.json

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3. Install ESP8266 Core

Update the index:

arduino-cli core update-index

Install ESP8266 support:

arduino-cli core install esp8266:esp8266

Verify installation:

arduino-cli core list

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4. Install Required Libraries

Install project dependencies:

arduino-cli lib install "ESP8266WiFi"
arduino-cli lib install "ArduinoJson"
arduino-cli lib install "DHTesp"
arduino-cli lib install "Adafruit_SH110X"

You can also install libraries automatically if they are listed in the project.

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5. Compile the Project

Navigate to the project folder and run:

arduino-cli compile \
  --fqbn esp8266:esp8266:nodemcuv2 \
  --build-property compiler.cpp.extra_flags="-Iapp -Idisplay -Iio -Isensors -Iwireless -Istorage" \
  -v .
arduino-cli compile --fqbn esp8266:esp8266:nodemcuv2 .

Example board types:

Board	FQBN
NodeMCU	esp8266:esp8266:nodemcuv2
Wemos D1 Mini	esp8266:esp8266:d1_mini
Generic ESP8266	esp8266:esp8266:generic

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6. Upload to the Board

Connect your ESP8266 via USB and check the port:

arduino-cli board list

Upload firmware:

arduino-cli upload -p /dev/ttyUSB0 --fqbn esp8266:esp8266:nodemcuv2

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7. Monitor Serial Output

arduino-cli monitor -p /dev/ttyUSB0 -c baudrate=115200

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License

Non-commercial license. See LICENSE file for details.