Go ESP32 Monitoring Application

This application is a backend service written in Go for monitoring an ESP32C3-based sensor system. It communicates with the ESP32 via a serial connection, collects sensor data, and stores it in a local SQLite database. The application also exposes a simple HTTP API for retrieving the data and controlling a relay.

Features

• Serial Communication: Establishes a connection with an ESP32C3 to send commands and receive sensor data in JSON format.
• Sensor Data Collection:
  • Temperature: Records both outdoor temperature (from the ESP32) and indoor temperature (from a separate HTTP endpoint) every 15 minutes.
  • Solar Power: Records solar panel voltage, current, and power at 15-minute intervals, but only between 7:15 AM and 7:30 PM.
• Local Database: Uses SQLite to store all sensor readings and relay state changes.
• Scheduled Pruning: Automatically deletes data older than 48 hours every 24 hours to manage disk space.
• Relay State Logging: A background job polls the ESP32 every 5 seconds and automatically records a new entry in the database whenever the relay's state changes. This ensures a complete history of all changes, regardless of how they were initiated.
• HTTP API: Provides various endpoints to fetch the latest sensor values, get historical data, and control a connected relay.

Prerequisites

• Go (version 1.18 or higher)
• An ESP32C3 device running the appropriate firmware for serial communication.
• A system with a serial port, such as an Orange Pi Zero 3 with Armbian.

Installation and Usage

1. Clone the repository:

   git clone <repository_url>
   cd <repository_folder>

2. Install dependencies:

   go mod tidy

3. Build the application:

   go build -o go.esp32.monitor

4. Run the application:

   ./go.esp32.monitor

5. Running as a Service (Recommended for servers like Orange Pi): For a more robust setup, you can run the application as a background service using systemd. A sample service file is provided in the documentation for reference.

   The service file go_esp32_monitor.service should look like this:

   [Unit]
   Description=Go ESP32 Monitoring Application
   After=network.target
   
   [Service]
   ExecStart=/home/wan/esp1-go/go.esp32.monitor
   WorkingDirectory=/home/wan/
   User=wan
   Restart=always
   RestartSec=3
   
   [Install]
   WantedBy=multi-user.target
   

Configuration

The indoor temperature sensor URL is currently hardcoded. You can change it in the main.go file:

const (
    // ...
    indoorTempURL = "http://192.168.1.4/i_temp"
)

API Endpoints

The application exposes the following HTTP endpoints on port 5000:

Endpoint	Method	Description
/r/on	POST	Turns the relay ON.
/r/off	POST	Turns the relay OFF.
/r/latest	GET	Gets the current state of the relay.
/o/latest	GET	Gets the latest outdoor temperature.
/i/latest	GET	Gets the latest indoor temperature.
/s/latest	GET	Gets the latest solar power readings.
/t/latest	GET	Gets the latest outdoor and indoor temps.
/t/24	GET	Gets temperature data for the last 24h.
/r/24	GET	Gets relay history for the last 24h.
/o/24	GET	Gets outdoor temperature for the last 24h.
/i/24	GET	Gets indoor temperature for the last 24h.
/s/24	GET	Gets solar power data for the last 24h.