Print a label on a Zebra TLP 2844 in Ruby. The printer is EPL/2 capable and connected via USB.

zebra.rb

# Print a label on a Zebra TLP 2844 in Ruby.
# The printer is EPL/2 capable and connected via USB.
# EPL/2 reference: http://www.zebra.com/apps/dlmanager?dlp=-227178c9720c025483893483886ea54a70963bb77ca94fcc1d65ce9394326ed960e43d023beba35831d5d9bfc1740296347157b5024977a&c=gb&l=en

# https://github.com/larskanis/libusb
require 'libusb'

# Select the printer by vendor ID and product ID.
# To get a list of connected devices, use 'lsusb'.
# 0a5f:0x000a identifies the Zebra TLP 2844.
usb = LIBUSB::Context.new
device = usb.devices(:idVendor => 0x0a5f, :idProduct => 0x000a).first

# Both an interface and endpoint must be selected on the printer.
# Each interface of an USB device can have one or more endpoints.
# Here is how to print information about interfaces and endpoints.
# (Use interface 0 and endpoint 6 for printing on the TLP 2844.)
# p device.interfaces
# p device.endpoints

# Open interface 0.
# The kernel might block the interface, try to release it, if so.
handle = device.open
begin
  handle.claim_interface(0)
rescue LIBUSB::ERROR_BUSY
  # Tell the kernel to release interface 0.
  handle.detach_kernel_driver(0)
  handle.claim_interface(0)
end

# Construct an EPL2 command.
# NOTE: append "\n" to the last command, "P1\n",
# otherwise, the printer won't start printing!
epl2_command = '%s\n' % [ %w(
  N
  A50,200,0,5,1,1,N,"EXAMPLE1"
  P1
).join("\n") ]

# Use bulk transfer to send the EPL2 command to the printer.
handle.bulk_transfer(endpoint: 6, dataOut: epl2_command)

# Cleanup.
handle.close