Test for NXT-PC communication via USB

USBInterface.py

# USB socket communication with LEGO Minstorms NXT -- adapted from nxt-python library
# Copyright (C) 2006, 2007  Douglas P Lau
# Copyright (C) 2009  Marcus Wanner
# Copyright (C) 2011  Paul Hollensen, Marcus Wanner
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

import usb, os

ID_VENDOR_LEGO = 0x0694
ID_PRODUCT_NXT = 0x0002

IN_ENDPOINT  = 0x82
OUT_ENDPOINT = 0x01

NXT_CONFIGURATION = 1
NXT_INTERFACE     = 0

TIMEOUT = 250

class USBInterface(object):
    'Object for USB connection to NXT'

    bsize = 60  # USB socket block size

    type = 'usb'

    def __init__(self, device, debug=False):
        self.device = device
        self.debug = debug

    def __str__(self):
        return 'USB (%s)' % (self.device.filename)

    def connect(self):
        'Use to connect to NXT.'
        if self.debug:
            print 'Connecting via USB...'
        try:
            if self.device.is_kernel_driver_active(NXT_INTERFACE):
                self.device.detach_kernel_driver(NXT_INTERFACE)
            self.device.set_configuration(NXT_CONFIGURATION)
        except Exception, err:
            if self.debug:
                print 'ERROR:usbsock:connect', err
            raise
        if self.debug:
            print 'Connected.'
        # return Brick(self)

    def close(self):
        'Use to close the connection.'
        if self.debug:
            print 'Closing USB connection...'
        self.device = None
        if self.debug:
            print 'USB connection closed.'

    def send(self, data):
        'Use to send raw data over USB connection ***ADVANCED USERS ONLY***'
        if self.debug:
            print 'Send:',
            print ':'.join('%02x' % ord(c) for c in data)
        self.device.write(OUT_ENDPOINT, data, NXT_INTERFACE)

    def recv(self):
        'Use to recieve raw data over USB connection ***ADVANCED USERS ONLY***'
        data = self.device.read(IN_ENDPOINT, 64, NXT_INTERFACE, TIMEOUT)
        if self.debug:
            print 'Recv:',
            print ':'.join('%02x' % (c & 0xFF) for c in data)
        # NOTE: bulkRead returns a tuple of ints ... make it sane
        return ''.join(chr(d & 0xFF) for d in data)

def find_bricks(host=None, name=None, debug=False):
    'Use to look for NXTs connected by USB only. ***ADVANCED USERS ONLY***'
    # FIXME: probably should check host (MAC)
    # if anyone knows how to do this, please file a bug report
    for device in usb.core.find(find_all=True, idVendor=ID_VENDOR_LEGO, idProduct=ID_PRODUCT_NXT):
        yield USBInterface(device, debug)


def main():
    # brick_usb = find_bricks(debug=True)
    try:
        brick_usb = next(find_bricks(debug=True))
    except usb.core.NoBackendError:
        raise_exception = True
    assert(raise_exception==0), "No NXT found..."
    # print(type(brick_usb), brick_usb)
    # brick_usb.connect()

if __name__ == '__main__':
    main()