Super simple driver for Royal LetterMaster

royal-print.py

import sys

import usb.core
import usb.util

import time

def initialize():
    # find our device
    dev = usb.core.find(idVendor=0x1a86, idProduct=0x7584)

    # was it found?
    if dev is None:
        raise ValueError('Device not found')
    
    # set the active configuration. With no arguments, the first
    # configuration will be the active one
    dev.set_configuration()

    # get an endpoint instance
    cfg = dev.get_active_configuration()
    intf = cfg[(0,0)]

    ep = usb.util.find_descriptor(
        intf,
        # match the first OUT endpoint
        custom_match = \
        lambda e: \
            usb.util.endpoint_direction(e.bEndpointAddress) == \
            usb.util.ENDPOINT_OUT)

    assert ep is not None
    
    return ep

def main():
    ep = initialize()
    to_print = sys.stdin.read()
    
    count = 0
    for c in to_print:
        ep.write(c)
        count = count + 1
        
        # Give it time to catch up
        if (count % 25 == 0):
            time.sleep(3)
            count = 0
            

if __name__ == "__main__":
    main()