Simple-Webcam

This sample provides a practical way to manage USB devices like webcams using a backend server built with FastAPI. The system handles events for connecting and disconnecting devices, while the frontend includes a toggle button to control the webcam feed. For more information about device types in Polyscope X, please see our documentation.

Note

This sample currently only works on a physical controller. It will fail on the simulator.

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Key Features

Backend (FastAPI)

• Device Add Endpoint (/device_add):
  • Processes information when a USB device is connected.
  • Decides whether to accept or reject the device.
  • Logs key details about the device and the action taken.
• Device Remove Endpoint (/device_remove):
  • Handles events when a USB device is disconnected.
  • Logs the removal for future reference.

Frontend

• Webcam Demo:
  • The frontend utilizes the ngx-webcam library. It runs a modified version of the ngx-webcam-demo with buttons to toggle the webcam and take a snapshot

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How It Works

1. Device Add Process:

   • When a USB device is plugged in, on_device_add.py runs automatically.
   • This script parses the device details and sends them to the /device_add endpoint.
   • The backend validates the details, checks the device type, and logs whether the device is accepted or rejected.

2. Device Remove Process:

   • When a USB device is unplugged, on_device_remove.py runs automatically.
   • This script sends the device information to the /device_remove endpoint.
   • The backend logs the removal for records or debugging.

3. Frontend Integration:

   • A toggle button lets users enable or disable the webcam feed.
   • Users can also take a snapshot which is displayed next to the active webcam feed.

API Endpoints

POST /device_add

• Purpose: Handles new device connections.
• Request Body (sample):

  {
    "idProduct": "2137",
    "idVendor": "0bda",
    "logicalDevices": [
      {"deviceNode": "/dev/video0", "major": 81, "minor": 0}
    ],
    "manufacturer": "HFGK-N",
    "product": "USB Camera",
    "serial": "200901010001",
    "urDeviceType": "VIDEO",
    "urDeviceAPIVersion": "0.1"
  }

• Response:
  • 200 OK with an exit_code field (0 = accepted, 1 = rejected).

POST /device_remove

• Purpose: Logs device disconnections.
• Request Body (sample):

  {
    "idProduct": "2137",
    "idVendor": "0bda",
    "logicalDevices": [
      {"deviceNode": "/dev/video0", "major": 81, "minor": 0}
    ],
    "manufacturer": "HFGK-N",
    "product": "USB Camera",
    "serial": "200901010001",
    "urDeviceType": "VIDEO",
    "urDeviceAPIVersion": "0.1"
  }

• Response:
  • 200 OK (exit codes are not relevant here).

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Logging System

Each component uses logging to keep track of events and actions:

• main.py: Logs device decisions and frontend requests.
• on_device_add.py: Logs initialization and device addition processing [currently not used]
• on_device_remove.py: Logs initialization and device removal events. [currently not used]

Example Logs:

2024-12-12 15:01:36,728 - main - DEBUG - Validated payload: idProduct='2137' idVendor='0bda' logicalDevices=[{'deviceNode': '/dev/video1', 'major': 81, 'minor': 1}, {'deviceNode': '/dev/video0', 'major': 81, 'minor': 0}] manufacturer='HFGK-N' product='USB Camera' serial='200901010001' urDeviceType='VIDEO' urDeviceAPIVersion='0.1'
2024-12-12 15:01:36,728 - main - INFO - Device was removed.

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Installation

To install the contribution type:

$ npm install

Build

To build the contribution type:

$ npm run build

Deploy

To deploy the contribution to the simulator type:

$ npm run install-urcap

Further help

Get more help from the included SDK documentation.

License

This project is released under the MIT License. See the LICENSE file for details.