lib/hidapi/engine.rb
def open(vendor_id, product_id, serial_number = nil, options = {})
      dev = get_device(vendor_id, product_id, serial_number, options)
      dev.open if dev
    end
def open(vendor_id, product_id, serial_number = nil, options = {})
      dev = get_device(vendor_id, product_id, serial_number, options)
      dev.open if dev
    end
Opens the first device with the specified vendor_id, product_id, and optionally serial_number.