QR Code Scanner

A Python library for reading QR codes from both HID (Human Interface Device) scanners and Serial devices. This library supports multiple connection types to accommodate different QR code scanner configurations.

Features

• HID Support: Treats QR code scanners as keyboard input devices and decodes their scanned data
• Serial Support: Direct serial communication for devices that output raw text data
• Support for multiple keyboard layouts (HID mode)
• Automatic character decoding
• Robust error handling
• Non-blocking and blocking read operations
• Device discovery utilities

Installation

Install using pip:

pip install qrcode-scanner

Or using Poetry:

poetry add qrcode-scanner

Requirements

• Python 3.10+
• hidapi (for HID devices)
• pyserial (for Serial devices)

Quick Start

HID Scanner Usage

from qrcode_scanner import HIDScanner
from qrcode_scanner.exceptions import DeviceConnectionError, DeviceNotFoundError, DeviceReadError

# Replace with your device's vendor ID and product ID
VENDOR_ID = 0x1D82
PRODUCT_ID = 0x5CA0

try:
    # Initialize and connect to the scanner
    scanner = HIDScanner(vendor_id=VENDOR_ID, product_id=PRODUCT_ID)
    scanner.connect()

    print("Connected to device")
    print("Manufacturer:", scanner.device.get_manufacturer_string())
    print("Product:", scanner.device.get_product_string())

    # Start reading QR codes
    while True:
        try:
            print("Listening for scans...")
            scanned_text = scanner.read()  # Blocking read operation
            if scanned_text:
                print("=== SCAN COMPLETE ===")
                print("Scanned text:", scanned_text)
        except DeviceNotFoundError:
            print("Device not found or not connected")
            break
        except (DeviceReadError, DeviceConnectionError) as e:
            print(f"Device error: {e}")
            break

except KeyboardInterrupt:
    print("Program terminated by user")
finally:
    scanner.close()
    print("HID device closed")

Serial Scanner Usage

from qrcode_scanner import SerialScanner, serial_ports
from qrcode_scanner.exceptions import DeviceConnectionError, DeviceNotConnectedError

# List available serial ports
print("Available serial ports:")
ports = serial_ports()
for port in ports:
    print(f"  - {port}")

# Configure the serial connection
port = "/dev/ttyACM0"  # Adjust for your system (Windows: "COM3", etc.)
baudrate = 9600

try:
    # Create and connect to the serial scanner
    scanner = SerialScanner(
        port=port,
        baudrate=baudrate,
        timeout=1  # timeout in seconds
    )

    scanner.connect()
    print(f"Connected to serial device on {port}")

    while True:
        print("Waiting for data...")
        try:
            # Read data from the scanner (blocking call)
            scanned_text = scanner.read()
            if scanned_text:
                print("=== SCAN COMPLETE ===")
                print("Scanned text:", scanned_text)
            else:
                print("No data received (timeout)")
        except DeviceNotConnectedError:
            print("Device not connected")
            break
        except DeviceConnectionError as e:
            print(f"Device connection error: {e}")
            break

except KeyboardInterrupt:
    print("Program terminated by user")
except DeviceConnectionError as e:
    print(f"Failed to connect to serial device: {e}")
finally:
    scanner.close()
    print("Serial device closed")

Serial Scanner Configuration

The SerialScanner class supports various configuration options:

scanner = SerialScanner(
    port="/dev/ttyACM0",  # Serial port
    baudrate=9600,        # Baud rate (default: 9600)
    parity=serial.PARITY_NONE,    # Parity (default: NONE)
    stopbits=serial.STOPBITS_ONE, # Stop bits (default: 1)
    bytesize=serial.EIGHTBITS,    # Byte size (default: 8)
    timeout=1             # Read timeout in seconds (default: 1)
)

Common baud rates for QR scanners: 9600, 19200, 38400, 115200

Error Handling

The library includes several exception classes to handle different error scenarios:

• DeviceNotFoundError: When the specified device cannot be found
• DeviceConnectionError: When there are issues connecting to the device
• DeviceNotConnectedError: When trying to read from a disconnected device
• DeviceReadError: When reading from the device fails
• UnknownCharacterError: When encountering unknown character codes (HID only)

Device Discovery

Finding HID Device IDs

To find your HID device's vendor and product IDs:

from qrcode_scanner import devices

# List all connected HID devices
for device in devices():
    print(f"Vendor ID: 0x{device['vendor_id']:04X}")
    print(f"Product ID: 0x{device['product_id']:04X}")
    print(f"Product Name: {device.get('product_string', 'N/A')}")
    print("---")

Finding Serial Ports

To discover available serial ports:

from qrcode_scanner import serial_ports

# List all available serial ports
ports = serial_ports()
for port in ports:
    print(f"Available port: {port}")

Choosing Between HID and Serial

Use HID Scanner when:

• Your QR scanner emulates a keyboard
• Scanner appears as an HID device in your system
• You need to decode keyboard scan codes

Use Serial Scanner when:

• Your QR scanner outputs raw text data over serial
• Scanner connects via USB-to-Serial adapter
• Device sends complete text strings followed by newline characters
• You want simpler, more direct communication

License

MIT License

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.