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rs485.py

#!/usr/bin/env python # RS485 support # # This file is part of pySerial. https://github.com/pyserial/pyserial # (C) 2015 Chris Liechti <cliechti@gmx.net> # # SPDX-License-Identifier: BSD-3-Clause """\ The settings for RS485 are stored in a dedicated object that can be applied to serial ports (where supported). NOTE: Some implementations may only support a subset of the settings. """ import time import serial class RS485Settings(object): def __init__( self, rts_level_for_tx=True, rts_level_for_rx=False, loopback=False, delay_before_tx=None, delay_before_rx=None): self.rts_level_for_tx = rts_level_for_tx self.rts_level_for_rx = rts_level_for_rx self.loopback = loopback self.delay_before_tx = delay_before_tx self.delay_before_rx = delay_before_rx class RS485(serial.Serial): """\ A subclass that replaces the write method with one that toggles RTS according to the RS485 settings. NOTE: This may work unreliably on some serial ports (control signals not synchronized or delayed compared to data). Using delays may be unreliable (varying times, larger than expected) as the OS may not support very fine grained delays (no smaller than in the order of tens of milliseconds). NOTE: Some implementations support this natively. Better performance can be expected when the native version is used. NOTE: The loopback property is ignored by this implementation. The actual behavior depends on the used hardware. Usage: ser = RS485(...) ser.rs485_mode = RS485Settings(...) ser.write(b'hello') """ def __init__(self, *args, **kwargs): super(RS485, self).__init__(*args, **kwargs) self._alternate_rs485_settings = None def write(self, b): """Write to port, controlling RTS before and after transmitting.""" if self._alternate_rs485_settings is not None: # apply level for TX and optional delay self.setRTS(self._alternate_rs485_settings.rts_level_for_tx) if self._alternate_rs485_settings.delay_before_tx is not None: time.sleep(self._alternate_rs485_settings.delay_before_tx) # write and wait for data to be written super(RS485, self).write(b) super(RS485, self).flush() # optional delay and apply level for RX if self._alternate_rs485_settings.delay_before_rx is not None: time.sleep(self._alternate_rs485_settings.delay_before_rx) self.setRTS(self._alternate_rs485_settings.rts_level_for_rx) else: super(RS485, self).write(b) # redirect where the property stores the settings so that underlying Serial # instance does not see them @property def rs485_mode(self): """\ Enable RS485 mode and apply new settings, set to None to disable. See serial.rs485.RS485Settings for more info about the value. """ return self._alternate_rs485_settings @rs485_mode.setter def rs485_mode(self, rs485_settings): self._alternate_rs485_settings = rs485_settings

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docroot: /home/induvedam/public_html

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curdir: /usr/lib/python3.9/site-packages/serial

	.		4096
	..		4096
X	__init__.py		3172
	__pycache__		4096
X	rfc2217.py		59486
X	rs485.py		3265
X	serialcli.py		9104
X	serialjava.py		8414
X	serialposix.py		31654
X	serialutil.py		21692
X	serialwin32.py		20087
	threaded		44
	tools		4096
	urlhandler		4096
X	win32.py		10853