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296 lines
9.1 KiB
296 lines
9.1 KiB
5 years ago
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#!/usr/bin/env python3
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#
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# Working with threading and pySerial
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#
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# This file is part of pySerial. https://github.com/pyserial/pyserial
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# (C) 2015-2016 Chris Liechti <cliechti@gmx.net>
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#
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# SPDX-License-Identifier: BSD-3-Clause
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"""\
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Support threading with serial ports.
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"""
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import serial
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import threading
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class Protocol(object):
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"""\
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Protocol as used by the ReaderThread. This base class provides empty
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implementations of all methods.
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"""
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def connection_made(self, transport):
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"""Called when reader thread is started"""
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def data_received(self, data):
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"""Called with snippets received from the serial port"""
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def connection_lost(self, exc):
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"""\
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Called when the serial port is closed or the reader loop terminated
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otherwise.
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"""
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if isinstance(exc, Exception):
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raise exc
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class Packetizer(Protocol):
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"""
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Read binary packets from serial port. Packets are expected to be terminated
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with a TERMINATOR byte (null byte by default).
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The class also keeps track of the transport.
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"""
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TERMINATOR = b'\0'
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def __init__(self):
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self.buffer = bytearray()
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self.transport = None
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def connection_made(self, transport):
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"""Store transport"""
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self.transport = transport
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def connection_lost(self, exc):
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"""Forget transport"""
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self.transport = None
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super(Packetizer, self).connection_lost(exc)
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def data_received(self, data):
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"""Buffer received data, find TERMINATOR, call handle_packet"""
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self.buffer.extend(data)
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while self.TERMINATOR in self.buffer:
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packet, self.buffer = self.buffer.split(self.TERMINATOR, 1)
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self.handle_packet(packet)
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def handle_packet(self, packet):
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"""Process packets - to be overridden by subclassing"""
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raise NotImplementedError('please implement functionality in handle_packet')
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class FramedPacket(Protocol):
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"""
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Read binary packets. Packets are expected to have a start and stop marker.
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The class also keeps track of the transport.
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"""
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START = b'('
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STOP = b')'
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def __init__(self):
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self.packet = bytearray()
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self.in_packet = False
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self.transport = None
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def connection_made(self, transport):
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"""Store transport"""
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self.transport = transport
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def connection_lost(self, exc):
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"""Forget transport"""
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self.transport = None
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self.in_packet = False
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del self.packet[:]
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super(FramedPacket, self).connection_lost(exc)
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def data_received(self, data):
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"""Find data enclosed in START/STOP, call handle_packet"""
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for byte in serial.iterbytes(data):
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if byte == self.START:
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self.in_packet = True
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elif byte == self.STOP:
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self.in_packet = False
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self.handle_packet(bytes(self.packet)) # make read-only copy
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del self.packet[:]
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elif self.in_packet:
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self.packet.extend(byte)
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else:
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self.handle_out_of_packet_data(byte)
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def handle_packet(self, packet):
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"""Process packets - to be overridden by subclassing"""
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raise NotImplementedError('please implement functionality in handle_packet')
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def handle_out_of_packet_data(self, data):
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"""Process data that is received outside of packets"""
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pass
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class LineReader(Packetizer):
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"""
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Read and write (Unicode) lines from/to serial port.
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The encoding is applied.
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"""
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TERMINATOR = b'\r\n'
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ENCODING = 'utf-8'
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UNICODE_HANDLING = 'replace'
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def handle_packet(self, packet):
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self.handle_line(packet.decode(self.ENCODING, self.UNICODE_HANDLING))
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def handle_line(self, line):
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"""Process one line - to be overridden by subclassing"""
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raise NotImplementedError('please implement functionality in handle_line')
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def write_line(self, text):
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"""
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Write text to the transport. ``text`` is a Unicode string and the encoding
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is applied before sending ans also the newline is append.
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"""
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# + is not the best choice but bytes does not support % or .format in py3 and we want a single write call
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self.transport.write(text.encode(self.ENCODING, self.UNICODE_HANDLING) + self.TERMINATOR)
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class ReaderThread(threading.Thread):
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"""\
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Implement a serial port read loop and dispatch to a Protocol instance (like
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the asyncio.Protocol) but do it with threads.
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Calls to close() will close the serial port but it is also possible to just
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stop() this thread and continue the serial port instance otherwise.
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"""
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def __init__(self, serial_instance, protocol_factory):
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"""\
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Initialize thread.
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Note that the serial_instance' timeout is set to one second!
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Other settings are not changed.
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"""
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super(ReaderThread, self).__init__()
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self.daemon = True
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self.serial = serial_instance
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self.protocol_factory = protocol_factory
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self.alive = True
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self._lock = threading.Lock()
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self._connection_made = threading.Event()
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self.protocol = None
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def stop(self):
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"""Stop the reader thread"""
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self.alive = False
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if hasattr(self.serial, 'cancel_read'):
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self.serial.cancel_read()
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self.join(2)
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def run(self):
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"""Reader loop"""
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if not hasattr(self.serial, 'cancel_read'):
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self.serial.timeout = 1
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self.protocol = self.protocol_factory()
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try:
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self.protocol.connection_made(self)
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except Exception as e:
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self.alive = False
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self.protocol.connection_lost(e)
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self._connection_made.set()
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return
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error = None
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self._connection_made.set()
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while self.alive and self.serial.is_open:
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try:
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# read all that is there or wait for one byte (blocking)
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data = self.serial.read(self.serial.in_waiting or 1)
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except serial.SerialException as e:
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# probably some I/O problem such as disconnected USB serial
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# adapters -> exit
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error = e
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break
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else:
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if data:
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# make a separated try-except for called used code
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try:
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self.protocol.data_received(data)
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except Exception as e:
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error = e
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break
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self.alive = False
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self.protocol.connection_lost(error)
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self.protocol = None
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def write(self, data):
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"""Thread safe writing (uses lock)"""
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with self._lock:
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self.serial.write(data)
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def close(self):
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"""Close the serial port and exit reader thread (uses lock)"""
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# use the lock to let other threads finish writing
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with self._lock:
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# first stop reading, so that closing can be done on idle port
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self.stop()
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self.serial.close()
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def connect(self):
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"""
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Wait until connection is set up and return the transport and protocol
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instances.
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"""
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if self.alive:
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self._connection_made.wait()
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if not self.alive:
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raise RuntimeError('connection_lost already called')
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return (self, self.protocol)
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else:
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raise RuntimeError('already stopped')
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# - - context manager, returns protocol
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def __enter__(self):
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"""\
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Enter context handler. May raise RuntimeError in case the connection
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could not be created.
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"""
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self.start()
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self._connection_made.wait()
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if not self.alive:
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raise RuntimeError('connection_lost already called')
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return self.protocol
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def __exit__(self, exc_type, exc_val, exc_tb):
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"""Leave context: close port"""
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self.close()
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# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
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# test
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if __name__ == '__main__':
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# pylint: disable=wrong-import-position
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import sys
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import time
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import traceback
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#~ PORT = 'spy:///dev/ttyUSB0'
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PORT = 'loop://'
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class PrintLines(LineReader):
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def connection_made(self, transport):
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super(PrintLines, self).connection_made(transport)
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sys.stdout.write('port opened\n')
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self.write_line('hello world')
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def handle_line(self, data):
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sys.stdout.write('line received: {!r}\n'.format(data))
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def connection_lost(self, exc):
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if exc:
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traceback.print_exc(exc)
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sys.stdout.write('port closed\n')
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ser = serial.serial_for_url(PORT, baudrate=115200, timeout=1)
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with ReaderThread(ser, PrintLines) as protocol:
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protocol.write_line('hello')
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time.sleep(2)
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# alternative usage
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ser = serial.serial_for_url(PORT, baudrate=115200, timeout=1)
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t = ReaderThread(ser, PrintLines)
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t.start()
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transport, protocol = t.connect()
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protocol.write_line('hello')
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time.sleep(2)
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t.close()
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