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Pi Monitor System Overview

Introduction

The Pi Monitor System is designed to display school-related information on monitors throughout the school using Raspberry Pis. The system consists of a server that manages content and configurations, clients running on Raspberry Pis that display the content, and a content management interface for easy updates. This document provides an overview of the system's architecture, components, and data flow.

System Architecture

The system is composed of several key components that work together to deliver content to the monitors:

  • Server: A FastAPI application that serves content and configurations.

  • Clients: Raspberry Pis that fetch and display content on monitors.

  • Content Management GUI: A web interface for updating monitor configurations.

  • Announcements Integration: Automated fetching and display of announcements from Google Docs.

Below is a high-level architecture diagram of the system:

flowchart TD
    subgraph Server
        A[FastAPI Application]
        B[Content Management GUI]
        C[Google Docs API Integration]
    end
    subgraph Clients
        D[Raspberry Pis]
    end
    E[Google Forms]
    F[Google Sheets]
    G[Google Docs]
    H[YouTube API]
    I[Weather API]

    E --> F
    F --> G
    G --> C
    C --> A
    B --> A
    A --> D
    D --> A
    D --> H
    H --> D
    D --> I
    I --> D
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Components

Server

The server is a FastAPI application (monitor.py) that handles:

  • Serving Content: Provides configurations and content to the clients.

  • Content Management GUI: Accessible via the /update endpoint, allowing authorized users to update configurations through a web interface.

  • Announcements Fetching: Retrieves announcements from a Google Docs document, which is updated via a Google Apps Script.

Key Files:

  • monitor.py: Main server application.
  • monitor_update.html: Content management GUI.
  • config/monitor.json: Stores current monitor configurations.
  • config/monitor_password.txt: Stores the bcrypt-hashed admin password for authentication.

Clients

Clients are Raspberry Pis connected to monitors, running scripts that:

  • Fetch Content: Retrieve configurations and content from the server.
  • Display Content: Use monitor.html and associated JavaScript files to display content.
  • Auto-Update: Pull updates from the GitHub repository to stay up-to-date.

Key Files:

  • pi/client: Starts the Chromium browser in kiosk mode to display content.
  • pi/client_manager: Manages client script execution and updates.
  • pi/startup: Initializes the client environment on boot.

External APIs

  • YouTube API: Used by clients to display YouTube videos and playlists.

  • Weather API (Open-Meteo): Used by clients to fetch and display current weather information.

Content Management GUI

The GUI allows administrators to update monitor configurations without directly editing configuration files.

  • Section Selection: Choose which section of the monitor to update (main, footer, sidebar).

  • Content Types: Select content type—image cycle, YouTube video/playlist, announcements, or info display.

  • File Uploads: Upload images directly through the interface.

Key Files:

  • monitor_update.html: Web page for the GUI.
  • static/js/monitor_update.js: Client-side logic for the GUI.

Announcements Integration

Announcements are managed through Google services:

  • Google Forms: Staff submit announcements via a form.
  • Google Sheets: Form responses are stored in a sheet.
  • Google Docs: A Google Apps Script (controller.js) updates a Google Doc with announcements.
  • Server Fetching: The server fetches the content of the Google Doc to display on monitors.

Key Files:

  • announcements/controller.js: Google Apps Script that updates the Google Doc.
  • monitor.py: Contains functions to fetch announcements from Google Docs.

Static Assets

  • HTML/CSS/JS: Frontend files that define the display on monitors.
  • Images: Stored in static/img/monitor/.
  • Audio: Stored in static/audio/.

Data Flow

The data flow between components is illustrated in the following sequence diagram:

sequenceDiagram
    participant GoogleSheet as Google Sheet
    participant GoogleDoc as Google Doc
    participant Server
    participant Client
    participant YouTubeAPI as YouTube API
    participant WeatherAPI as Weather API


    GoogleSheet->>GoogleDoc: Update via Apps Script
    loop Every 5 minutes
        Server->>GoogleDoc: Fetch Announcements
        GoogleDoc->>Server: Return Content
    end
    loop Client Refresh Interval
        Client->>Server: Fetch Configurations
        Server->>Client: Send Configurations and Content
        par If YouTube Content
            Client->>YouTubeAPI: Request Video/Playlist
            YouTubeAPI->>Client: Stream Content
        end
        par If Weather Info
            Client->>WeatherAPI: Request Weather Data
            WeatherAPI->>Client: Send Weather Data
        end
        Client->>Client: Display Content
    end
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Content Update Flow

  1. Announcements Submission:

    • Staff submit announcements through a Google Form.
    • Responses are saved in a Google Sheet.

  2. Announcements Processing:

    • A Google Apps Script (controller.js) processes the Google Sheet data.
    • The script updates a Google Doc with the latest announcements.

  3. Server Fetching Announcements:

    • The server periodically fetches the Google Doc content using the Google Docs API.
    • Announcements are cached and served to clients upon request.

  4. Clients Fetching Configurations:

    • Clients request the latest configurations and content from the server.
    • The server responds with the current monitor.json configurations and announcements.

  5. Displaying Content:

    • Clients display the content based on the received configurations.
    • Content types include image cycles, YouTube videos/playlists, announcements, and info displays.

Limitations

  • No SSH Access:

    • Due to network and physical constraints, remote access to Raspberry Pis is not available.
    • Updates and maintenance are performed via the auto-update mechanism.

  • Security Considerations:

    • The system operates within the school's internal network.
    • Authentication for the content management GUI uses HTTP Basic Auth over HTTP.