# The MIT License (MIT)
#
# Copyright (c) 2017 Carter Nelson for Adafruit Industries
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# THE SOFTWARE.
"""
`OneWire Device`
====================================================
Provides access to a single device on the 1-Wire bus.
* Author(s): Carter Nelson
"""
__version__ = "0.0.0-auto.0"
__repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_OneWire.git"
_MATCH_ROM = b'\x55'
[docs]class OneWireDevice(object):
"""A class to represent a single device on the 1-Wire bus."""
def __init__(self, bus, address):
self._bus = bus
self._address = address
def __enter__(self):
self._select_rom()
return self
def __exit__(self, *exc):
return False
[docs] def readinto(self, buf, *, start=0, end=None):
"""
Read into ``buf`` from the device. The number of bytes read will be the
length of ``buf``.
If ``start`` or ``end`` is provided, then the buffer will be sliced
as if ``buf[start:end]``. This will not cause an allocation like
``buf[start:end]`` will so it saves memory.
:param bytearray buf: buffer to write into
:param int start: Index to start writing at
:param int end: Index to write up to but not include
"""
self._bus.readinto(buf, start=start, end=end)
if start == 0 and end is None and len(buf) >= 8:
if self._bus.crc8(buf):
raise RuntimeError('CRC error.')
[docs] def write(self, buf, *, start=0, end=None):
"""
Write the bytes from ``buf`` to the device.
If ``start`` or ``end`` is provided, then the buffer will be sliced
as if ``buffer[start:end]``. This will not cause an allocation like
``buffer[start:end]`` will so it saves memory.
:param bytearray buf: buffer containing the bytes to write
:param int start: Index to start writing from
:param int end: Index to read up to but not include
"""
return self._bus.write(buf, start=start, end=end)
def _select_rom(self):
self._bus.reset()
self.write(_MATCH_ROM)
self.write(self._address.rom)