Linux Python code to read from a USB barcode scanner directly.
This uses the pyusb module to read a USB-HID barcode scanner in Linux.
This barcode scanner acts like a keyboard so scanning a bar code types out the data as if you were typing. Easy-peesy, right?
Well, the problem is, I don't want a console user logged into the computer. For security reasons, I want my program to just read directly from the barcode reader as if it were some other data device without having to read "keyboard input". Otherwise, someone can just plug in a keyboard, hit Ctrl-C, and get a console prompt to control the computer. (Yeah, there's ways to disable this but the method presented here is probably more bullet proof.)
So this program detaches the device from the kernel so it will not "type" anything, and then reads directly from the barcode scanner. It does not need any special drivers for the barcode scanner.
This uses pyusb to do low-level USB comm. See https://github.com/pyusb/pyusb for installation requirements. Basically, you need to install pyusb:
pip install pyusbTo install the backend that pyusb uses, you can use libusb (among others):
sudo apt install libusb-1.0-0-devYou need to make sure your user is a member of plugdev to use USB devices (in Debian linux):
sudo addgroup <myuser> plugdevYou also need to create a udev rule to allow all users to access the
barcode scanner. In /etc/udev/rules.d, create a file that ends in .rules
such as 55-barcode-scanner.rules with these contents:
# Set permissions to let anyone use barcode scanner
SUBSYSTEM=="usb", ATTR{idVendor}=="05e0", ATTR{idProduct}=="1200", MODE="666"This tells the computer, if a USB device with Vendor ID = 0x05e0 and Product ID = 0x1200 is plugged in (which is this LS2208 Symbol/Motorola barcode scanner), then set mode to "666" (any user can read and write to the device).
To get the updated permissions, reboot or just unplug and replug the barcode scanner.
This was tested on a Raspberry Pi Zero W running Rasbian Stretch Lite. USB interface was using a USB-OTG cable. This should work as-is with any Debian-based Linux system.
Copyright (c) 2019 Vince Patron, http://vince.patronweb.com
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