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# nxt.backend.devfile module -- Device file backend
# Copyright (C) 2013 Dave Churchill, Marcus Wanner
# Copyright (C) 2021 Nicolas Schodet
#
# 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 glob
import logging
import platform
import struct
import tty
import nxt.brick
logger = logging.getLogger(__name__)
class DevFileSock:
"""Device file socket connected to a NXT brick."""
#: Block size.
bsize = 118
#: Connection type, used to evaluate latency.
type = "bluetooth"
def __init__(self, filename):
self._filename = filename
def __str__(self):
return f"DevFile ({self._filename})"
def connect(self):
"""Connect to NXT brick.
:return: Connected brick.
:rtype: Brick
"""
logger.info("connecting via %s", self._filename)
self._device = open(self._filename, "r+b", buffering=0)
tty.setraw(self._device)
return nxt.brick.Brick(self)
def close(self):
"""Close the connection."""
if self._device is not None:
logger.info("closing %s connection", self._filename)
self._device.close()
self._device = None
def send(self, data):
"""Send raw data.
:param bytes data: Data to send.
"""
data = struct.pack("<H", len(data)) + data
logger.debug("send: %s", data.hex())
self._device.write(data)
def recv(self):
"""Receive raw data.
:return: Received data.
:rtype: bytes
"""
data = self._device.read(2)
logger.debug("recv: %s", data.hex())
(plen,) = struct.unpack("<H", data)
data = self._device.read(plen)
logger.debug("recv: %s", data.hex())
return data
class Backend:
"""Device file backend.
This uses a device file present on Linux or macOS /dev file system, which allows to
connect to the NXT brick without needing a Bluetooth python package.
You only need to use this backend if the :mod:`~nxt.backend.bluetooth` backend is
not working for you.
On Linux, you need to pair the NXT brick, then you can use the rfcomm tool::
sudo rfcomm bind 0 00:16:53:01:02:03
Where ``00:16:53:01:02:03`` is the Bluetooth address of your NXT brick. This will
create a ``/dev/rfcomm0`` device file which can be used to communicate with the NXT
brick.
On macOS, you need to pair the NXT brick, then open Bluetooth preferences, select
the NXT brick, click “Edit serial ports”. It should show “NXT-DevB-1”. If not, add
a serial port using:
- Port name: NXT-DevB-1
- Device service: Dev B
- Port type: RS-232
This should create a ``/dev/tty.NXT-DevB-1`` device file which can be used to
communicate with the NXT brick.
"""
def find(self, name=None, filename=None, **kwargs):
"""Find bricks connected using Bluetooth using device file.
:param name: Brick name (example: ``"NXT"``).
:type name: str or None
:param filename: Device file name (example: ``"/dev/rfcomm0"``).
:type filename: str or None
:param kwargs: Other parameters are ignored.
:return: Iterator over all found bricks.
:rtype: Iterator[Brick]
"""
if filename:
matches = [filename]
else:
system = platform.system()
if system == "Linux":
matches = glob.glob("/dev/rfcomm*")
elif system == "Darwin":
if name:
matches = glob.glob("/dev/*%s*" % name)
else:
matches = glob.glob("/dev/*-DevB*")
else:
matches = []
for match in matches:
sock = DevFileSock(match)
try:
brick = sock.connect()
except OSError:
logger.exception("failed to connect to device %s", sock)
else:
yield brick
def get_backend():
"""Get an instance of the device file backend.
:return: Device file backend.
:rtype: Backend
"""
return Backend()
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