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Edit File: serialposix.py
#!/usr/bin/env python # # backend for serial IO for POSIX compatible systems, like Linux, OSX # # This file is part of pySerial. https://github.com/pyserial/pyserial # (C) 2001-2016 Chris Liechti <cliechti@gmx.net> # # SPDX-License-Identifier: BSD-3-Clause # # parts based on code from Grant B. Edwards <grante@visi.com>: # ftp://ftp.visi.com/users/grante/python/PosixSerial.py # # references: http://www.easysw.com/~mike/serial/serial.html # Collection of port names (was previously used by number_to_device which was # removed. # - Linux /dev/ttyS%d (confirmed) # - cygwin/win32 /dev/com%d (confirmed) # - openbsd (OpenBSD) /dev/cua%02d # - bsd*, freebsd* /dev/cuad%d # - darwin (OS X) /dev/cuad%d # - netbsd /dev/dty%02d (NetBSD 1.6 testing by Erk) # - irix (IRIX) /dev/ttyf%d (partially tested) names depending on flow control # - hp (HP-UX) /dev/tty%dp0 (not tested) # - sunos (Solaris/SunOS) /dev/tty%c (letters, 'a'..'z') (confirmed) # - aix (AIX) /dev/tty%d # pylint: disable=abstract-method import errno import fcntl import os import select import struct import sys import termios import serial from serial.serialutil import SerialBase, SerialException, to_bytes, \ portNotOpenError, writeTimeoutError, Timeout class PlatformSpecificBase(object): BAUDRATE_CONSTANTS = {} def _set_special_baudrate(self, baudrate): raise NotImplementedError('non-standard baudrates are not supported on this platform') def _set_rs485_mode(self, rs485_settings): raise NotImplementedError('RS485 not supported on this platform') # some systems support an extra flag to enable the two in POSIX unsupported # paritiy settings for MARK and SPACE CMSPAR = 0 # default, for unsupported platforms, override below # try to detect the OS so that a device can be selected... # this code block should supply a device() and set_special_baudrate() function # for the platform plat = sys.platform.lower() if plat[:5] == 'linux': # Linux (confirmed) # noqa import array # extra termios flags CMSPAR = 0o10000000000 # Use "stick" (mark/space) parity # baudrate ioctls TCGETS2 = 0x802C542A TCSETS2 = 0x402C542B BOTHER = 0o010000 # RS485 ioctls TIOCGRS485 = 0x542E TIOCSRS485 = 0x542F SER_RS485_ENABLED = 0b00000001 SER_RS485_RTS_ON_SEND = 0b00000010 SER_RS485_RTS_AFTER_SEND = 0b00000100 SER_RS485_RX_DURING_TX = 0b00010000 class PlatformSpecific(PlatformSpecificBase): BAUDRATE_CONSTANTS = { 0: 0o000000, # hang up 50: 0o000001, 75: 0o000002, 110: 0o000003, 134: 0o000004, 150: 0o000005, 200: 0o000006, 300: 0o000007, 600: 0o000010, 1200: 0o000011, 1800: 0o000012, 2400: 0o000013, 4800: 0o000014, 9600: 0o000015, 19200: 0o000016, 38400: 0o000017, 57600: 0o010001, 115200: 0o010002, 230400: 0o010003, 460800: 0o010004, 500000: 0o010005, 576000: 0o010006, 921600: 0o010007, 1000000: 0o010010, 1152000: 0o010011, 1500000: 0o010012, 2000000: 0o010013, 2500000: 0o010014, 3000000: 0o010015, 3500000: 0o010016, 4000000: 0o010017 } def _set_special_baudrate(self, baudrate): # right size is 44 on x86_64, allow for some growth buf = array.array('i', [0] * 64) try: # get serial_struct fcntl.ioctl(self.fd, TCGETS2, buf) # set custom speed buf[2] &= ~termios.CBAUD buf[2] |= BOTHER buf[9] = buf[10] = baudrate # set serial_struct fcntl.ioctl(self.fd, TCSETS2, buf) except IOError as e: raise ValueError('Failed to set custom baud rate ({}): {}'.format(baudrate, e)) def _set_rs485_mode(self, rs485_settings): buf = array.array('i', [0] * 8) # flags, delaytx, delayrx, padding try: fcntl.ioctl(self.fd, TIOCGRS485, buf) buf[0] |= SER_RS485_ENABLED if rs485_settings is not None: if rs485_settings.loopback: buf[0] |= SER_RS485_RX_DURING_TX else: buf[0] &= ~SER_RS485_RX_DURING_TX if rs485_settings.rts_level_for_tx: buf[0] |= SER_RS485_RTS_ON_SEND else: buf[0] &= ~SER_RS485_RTS_ON_SEND if rs485_settings.rts_level_for_rx: buf[0] |= SER_RS485_RTS_AFTER_SEND else: buf[0] &= ~SER_RS485_RTS_AFTER_SEND if rs485_settings.delay_before_tx is not None: buf[1] = int(rs485_settings.delay_before_tx * 1000) if rs485_settings.delay_before_rx is not None: buf[2] = int(rs485_settings.delay_before_rx * 1000) else: buf[0] = 0 # clear SER_RS485_ENABLED fcntl.ioctl(self.fd, TIOCSRS485, buf) except IOError as e: raise ValueError('Failed to set RS485 mode: {}'.format(e)) elif plat == 'cygwin': # cygwin/win32 (confirmed) class PlatformSpecific(PlatformSpecificBase): BAUDRATE_CONSTANTS = { 128000: 0x01003, 256000: 0x01005, 500000: 0x01007, 576000: 0x01008, 921600: 0x01009, 1000000: 0x0100a, 1152000: 0x0100b, 1500000: 0x0100c, 2000000: 0x0100d, 2500000: 0x0100e, 3000000: 0x0100f } elif plat[:6] == 'darwin': # OS X import array IOSSIOSPEED = 0x80045402 # _IOW('T', 2, speed_t) class PlatformSpecific(PlatformSpecificBase): osx_version = os.uname()[2].split('.') # Tiger or above can support arbitrary serial speeds if int(osx_version[0]) >= 8: def _set_special_baudrate(self, baudrate): # use IOKit-specific call to set up high speeds buf = array.array('i', [baudrate]) fcntl.ioctl(self.fd, IOSSIOSPEED, buf, 1) elif plat[:3] == 'bsd' or \ plat[:7] == 'freebsd' or \ plat[:6] == 'netbsd' or \ plat[:7] == 'openbsd': class ReturnBaudrate(object): def __getitem__(self, key): return key class PlatformSpecific(PlatformSpecificBase): # Only tested on FreeBSD: # The baud rate may be passed in as # a literal value. BAUDRATE_CONSTANTS = ReturnBaudrate() else: class PlatformSpecific(PlatformSpecificBase): pass # load some constants for later use. # try to use values from termios, use defaults from linux otherwise TIOCMGET = getattr(termios, 'TIOCMGET', 0x5415) TIOCMBIS = getattr(termios, 'TIOCMBIS', 0x5416) TIOCMBIC = getattr(termios, 'TIOCMBIC', 0x5417) TIOCMSET = getattr(termios, 'TIOCMSET', 0x5418) # TIOCM_LE = getattr(termios, 'TIOCM_LE', 0x001) TIOCM_DTR = getattr(termios, 'TIOCM_DTR', 0x002) TIOCM_RTS = getattr(termios, 'TIOCM_RTS', 0x004) # TIOCM_ST = getattr(termios, 'TIOCM_ST', 0x008) # TIOCM_SR = getattr(termios, 'TIOCM_SR', 0x010) TIOCM_CTS = getattr(termios, 'TIOCM_CTS', 0x020) TIOCM_CAR = getattr(termios, 'TIOCM_CAR', 0x040) TIOCM_RNG = getattr(termios, 'TIOCM_RNG', 0x080) TIOCM_DSR = getattr(termios, 'TIOCM_DSR', 0x100) TIOCM_CD = getattr(termios, 'TIOCM_CD', TIOCM_CAR) TIOCM_RI = getattr(termios, 'TIOCM_RI', TIOCM_RNG) # TIOCM_OUT1 = getattr(termios, 'TIOCM_OUT1', 0x2000) # TIOCM_OUT2 = getattr(termios, 'TIOCM_OUT2', 0x4000) if hasattr(termios, 'TIOCINQ'): TIOCINQ = termios.TIOCINQ else: TIOCINQ = getattr(termios, 'FIONREAD', 0x541B) TIOCOUTQ = getattr(termios, 'TIOCOUTQ', 0x5411) TIOCM_zero_str = struct.pack('I', 0) TIOCM_RTS_str = struct.pack('I', TIOCM_RTS) TIOCM_DTR_str = struct.pack('I', TIOCM_DTR) TIOCSBRK = getattr(termios, 'TIOCSBRK', 0x5427) TIOCCBRK = getattr(termios, 'TIOCCBRK', 0x5428) class Serial(SerialBase, PlatformSpecific): """\ Serial port class POSIX implementation. Serial port configuration is done with termios and fcntl. Runs on Linux and many other Un*x like systems. """ def open(self): """\ Open port with current settings. This may throw a SerialException if the port cannot be opened.""" if self._port is None: raise SerialException("Port must be configured before it can be used.") if self.is_open: raise SerialException("Port is already open.") self.fd = None # open try: self.fd = os.open(self.portstr, os.O_RDWR | os.O_NOCTTY | os.O_NONBLOCK) except OSError as msg: self.fd = None raise SerialException(msg.errno, "could not open port {}: {}".format(self._port, msg)) #~ fcntl.fcntl(self.fd, fcntl.F_SETFL, 0) # set blocking try: self._reconfigure_port(force_update=True) except: try: os.close(self.fd) except: # ignore any exception when closing the port # also to keep original exception that happened when setting up pass self.fd = None raise else: self.is_open = True try: if not self._dsrdtr: self._update_dtr_state() if not self._rtscts: self._update_rts_state() except IOError as e: if e.errno in (errno.EINVAL, errno.ENOTTY): # ignore Invalid argument and Inappropriate ioctl pass else: raise self.reset_input_buffer() self.pipe_abort_read_r, self.pipe_abort_read_w = os.pipe() self.pipe_abort_write_r, self.pipe_abort_write_w = os.pipe() fcntl.fcntl(self.pipe_abort_read_r, fcntl.F_SETFL, os.O_NONBLOCK) fcntl.fcntl(self.pipe_abort_write_r, fcntl.F_SETFL, os.O_NONBLOCK) def _reconfigure_port(self, force_update=False): """Set communication parameters on opened port.""" if self.fd is None: raise SerialException("Can only operate on a valid file descriptor") # if exclusive lock is requested, create it before we modify anything else if self._exclusive is not None: if self._exclusive: try: fcntl.flock(self.fd, fcntl.LOCK_EX | fcntl.LOCK_NB) except IOError as msg: raise SerialException(msg.errno, "Could not exclusively lock port {}: {}".format(self._port, msg)) else: fcntl.flock(self.fd, fcntl.LOCK_UN) custom_baud = None vmin = vtime = 0 # timeout is done via select if self._inter_byte_timeout is not None: vmin = 1 vtime = int(self._inter_byte_timeout * 10) try: orig_attr = termios.tcgetattr(self.fd) iflag, oflag, cflag, lflag, ispeed, ospeed, cc = orig_attr except termios.error as msg: # if a port is nonexistent but has a /dev file, it'll fail here raise SerialException("Could not configure port: {}".format(msg)) # set up raw mode / no echo / binary cflag |= (termios.CLOCAL | termios.CREAD) lflag &= ~(termios.ICANON | termios.ECHO | termios.ECHOE | termios.ECHOK | termios.ECHONL | termios.ISIG | termios.IEXTEN) # |termios.ECHOPRT for flag in ('ECHOCTL', 'ECHOKE'): # netbsd workaround for Erk if hasattr(termios, flag): lflag &= ~getattr(termios, flag) oflag &= ~(termios.OPOST | termios.ONLCR | termios.OCRNL) iflag &= ~(termios.INLCR | termios.IGNCR | termios.ICRNL | termios.IGNBRK) if hasattr(termios, 'IUCLC'): iflag &= ~termios.IUCLC if hasattr(termios, 'PARMRK'): iflag &= ~termios.PARMRK # setup baud rate try: ispeed = ospeed = getattr(termios, 'B{}'.format(self._baudrate)) except AttributeError: try: ispeed = ospeed = self.BAUDRATE_CONSTANTS[self._baudrate] except KeyError: #~ raise ValueError('Invalid baud rate: %r' % self._baudrate) # may need custom baud rate, it isn't in our list. ispeed = ospeed = getattr(termios, 'B38400') try: custom_baud = int(self._baudrate) # store for later except ValueError: raise ValueError('Invalid baud rate: {!r}'.format(self._baudrate)) else: if custom_baud < 0: raise ValueError('Invalid baud rate: {!r}'.format(self._baudrate)) # setup char len cflag &= ~termios.CSIZE if self._bytesize == 8: cflag |= termios.CS8 elif self._bytesize == 7: cflag |= termios.CS7 elif self._bytesize == 6: cflag |= termios.CS6 elif self._bytesize == 5: cflag |= termios.CS5 else: raise ValueError('Invalid char len: {!r}'.format(self._bytesize)) # setup stop bits if self._stopbits == serial.STOPBITS_ONE: cflag &= ~(termios.CSTOPB) elif self._stopbits == serial.STOPBITS_ONE_POINT_FIVE: cflag |= (termios.CSTOPB) # XXX same as TWO.. there is no POSIX support for 1.5 elif self._stopbits == serial.STOPBITS_TWO: cflag |= (termios.CSTOPB) else: raise ValueError('Invalid stop bit specification: {!r}'.format(self._stopbits)) # setup parity iflag &= ~(termios.INPCK | termios.ISTRIP) if self._parity == serial.PARITY_NONE: cflag &= ~(termios.PARENB | termios.PARODD | CMSPAR) elif self._parity == serial.PARITY_EVEN: cflag &= ~(termios.PARODD | CMSPAR) cflag |= (termios.PARENB) elif self._parity == serial.PARITY_ODD: cflag &= ~CMSPAR cflag |= (termios.PARENB | termios.PARODD) elif self._parity == serial.PARITY_MARK and CMSPAR: cflag |= (termios.PARENB | CMSPAR | termios.PARODD) elif self._parity == serial.PARITY_SPACE and CMSPAR: cflag |= (termios.PARENB | CMSPAR) cflag &= ~(termios.PARODD) else: raise ValueError('Invalid parity: {!r}'.format(self._parity)) # setup flow control # xonxoff if hasattr(termios, 'IXANY'): if self._xonxoff: iflag |= (termios.IXON | termios.IXOFF) # |termios.IXANY) else: iflag &= ~(termios.IXON | termios.IXOFF | termios.IXANY) else: if self._xonxoff: iflag |= (termios.IXON | termios.IXOFF) else: iflag &= ~(termios.IXON | termios.IXOFF) # rtscts if hasattr(termios, 'CRTSCTS'): if self._rtscts: cflag |= (termios.CRTSCTS) else: cflag &= ~(termios.CRTSCTS) elif hasattr(termios, 'CNEW_RTSCTS'): # try it with alternate constant name if self._rtscts: cflag |= (termios.CNEW_RTSCTS) else: cflag &= ~(termios.CNEW_RTSCTS) # XXX should there be a warning if setting up rtscts (and xonxoff etc) fails?? # buffer # vmin "minimal number of characters to be read. 0 for non blocking" if vmin < 0 or vmin > 255: raise ValueError('Invalid vmin: {!r}'.format(vmin)) cc[termios.VMIN] = vmin # vtime if vtime < 0 or vtime > 255: raise ValueError('Invalid vtime: {!r}'.format(vtime)) cc[termios.VTIME] = vtime # activate settings if force_update or [iflag, oflag, cflag, lflag, ispeed, ospeed, cc] != orig_attr: termios.tcsetattr( self.fd, termios.TCSANOW, [iflag, oflag, cflag, lflag, ispeed, ospeed, cc]) # apply custom baud rate, if any if custom_baud is not None: self._set_special_baudrate(custom_baud) if self._rs485_mode is not None: self._set_rs485_mode(self._rs485_mode) def close(self): """Close port""" if self.is_open: if self.fd is not None: os.close(self.fd) self.fd = None os.close(self.pipe_abort_read_w) os.close(self.pipe_abort_read_r) os.close(self.pipe_abort_write_w) os.close(self.pipe_abort_write_r) self.pipe_abort_read_r, self.pipe_abort_read_w = None, None self.pipe_abort_write_r, self.pipe_abort_write_w = None, None self.is_open = False # - - - - - - - - - - - - - - - - - - - - - - - - @property def in_waiting(self): """Return the number of bytes currently in the input buffer.""" #~ s = fcntl.ioctl(self.fd, termios.FIONREAD, TIOCM_zero_str) s = fcntl.ioctl(self.fd, TIOCINQ, TIOCM_zero_str) return struct.unpack('I', s)[0] # select based implementation, proved to work on many systems def read(self, size=1): """\ Read size bytes from the serial port. If a timeout is set it may return less characters as requested. With no timeout it will block until the requested number of bytes is read. """ if not self.is_open: raise portNotOpenError read = bytearray() timeout = Timeout(self._timeout) while len(read) < size: try: ready, _, _ = select.select([self.fd, self.pipe_abort_read_r], [], [], timeout.time_left()) if self.pipe_abort_read_r in ready: os.read(self.pipe_abort_read_r, 1000) break # If select was used with a timeout, and the timeout occurs, it # returns with empty lists -> thus abort read operation. # For timeout == 0 (non-blocking operation) also abort when # there is nothing to read. if not ready: break # timeout buf = os.read(self.fd, size - len(read)) # read should always return some data as select reported it was # ready to read when we get to this point. if not buf: # Disconnected devices, at least on Linux, show the # behavior that they are always ready to read immediately # but reading returns nothing. raise SerialException( 'device reports readiness to read but returned no data ' '(device disconnected or multiple access on port?)') read.extend(buf) except OSError as e: # this is for Python 3.x where select.error is a subclass of # OSError ignore BlockingIOErrors and EINTR. other errors are shown # https://www.python.org/dev/peps/pep-0475. if e.errno not in (errno.EAGAIN, errno.EALREADY, errno.EWOULDBLOCK, errno.EINPROGRESS, errno.EINTR): raise SerialException('read failed: {}'.format(e)) except select.error as e: # this is for Python 2.x # ignore BlockingIOErrors and EINTR. all errors are shown # see also http://www.python.org/dev/peps/pep-3151/#select if e[0] not in (errno.EAGAIN, errno.EALREADY, errno.EWOULDBLOCK, errno.EINPROGRESS, errno.EINTR): raise SerialException('read failed: {}'.format(e)) if timeout.expired(): break return bytes(read) def cancel_read(self): if self.is_open: os.write(self.pipe_abort_read_w, b"x") def cancel_write(self): if self.is_open: os.write(self.pipe_abort_write_w, b"x") def write(self, data): """Output the given byte string over the serial port.""" if not self.is_open: raise portNotOpenError d = to_bytes(data) tx_len = length = len(d) timeout = Timeout(self._write_timeout) while tx_len > 0: try: n = os.write(self.fd, d) if timeout.is_non_blocking: # Zero timeout indicates non-blocking - simply return the # number of bytes of data actually written return n elif not timeout.is_infinite: # when timeout is set, use select to wait for being ready # with the time left as timeout if timeout.expired(): raise writeTimeoutError abort, ready, _ = select.select([self.pipe_abort_write_r], [self.fd], [], timeout.time_left()) if abort: os.read(self.pipe_abort_write_r, 1000) break if not ready: raise writeTimeoutError else: assert timeout.time_left() is None # wait for write operation abort, ready, _ = select.select([self.pipe_abort_write_r], [self.fd], [], None) if abort: os.read(self.pipe_abort_write_r, 1) break if not ready: raise SerialException('write failed (select)') d = d[n:] tx_len -= n except SerialException: raise except OSError as e: # this is for Python 3.x where select.error is a subclass of # OSError ignore BlockingIOErrors and EINTR. other errors are shown # https://www.python.org/dev/peps/pep-0475. if e.errno not in (errno.EAGAIN, errno.EALREADY, errno.EWOULDBLOCK, errno.EINPROGRESS, errno.EINTR): raise SerialException('write failed: {}'.format(e)) except select.error as e: # this is for Python 2.x # ignore BlockingIOErrors and EINTR. all errors are shown # see also http://www.python.org/dev/peps/pep-3151/#select if e[0] not in (errno.EAGAIN, errno.EALREADY, errno.EWOULDBLOCK, errno.EINPROGRESS, errno.EINTR): raise SerialException('write failed: {}'.format(e)) if not timeout.is_non_blocking and timeout.expired(): raise writeTimeoutError return length - len(d) def flush(self): """\ Flush of file like objects. In this case, wait until all data is written. """ if not self.is_open: raise portNotOpenError termios.tcdrain(self.fd) def reset_input_buffer(self): """Clear input buffer, discarding all that is in the buffer.""" if not self.is_open: raise portNotOpenError termios.tcflush(self.fd, termios.TCIFLUSH) def reset_output_buffer(self): """\ Clear output buffer, aborting the current output and discarding all that is in the buffer. """ if not self.is_open: raise portNotOpenError termios.tcflush(self.fd, termios.TCOFLUSH) def send_break(self, duration=0.25): """\ Send break condition. Timed, returns to idle state after given duration. """ if not self.is_open: raise portNotOpenError termios.tcsendbreak(self.fd, int(duration / 0.25)) def _update_break_state(self): """\ Set break: Controls TXD. When active, no transmitting is possible. """ if self._break_state: fcntl.ioctl(self.fd, TIOCSBRK) else: fcntl.ioctl(self.fd, TIOCCBRK) def _update_rts_state(self): """Set terminal status line: Request To Send""" if self._rts_state: fcntl.ioctl(self.fd, TIOCMBIS, TIOCM_RTS_str) else: fcntl.ioctl(self.fd, TIOCMBIC, TIOCM_RTS_str) def _update_dtr_state(self): """Set terminal status line: Data Terminal Ready""" if self._dtr_state: fcntl.ioctl(self.fd, TIOCMBIS, TIOCM_DTR_str) else: fcntl.ioctl(self.fd, TIOCMBIC, TIOCM_DTR_str) @property def cts(self): """Read terminal status line: Clear To Send""" if not self.is_open: raise portNotOpenError s = fcntl.ioctl(self.fd, TIOCMGET, TIOCM_zero_str) return struct.unpack('I', s)[0] & TIOCM_CTS != 0 @property def dsr(self): """Read terminal status line: Data Set Ready""" if not self.is_open: raise portNotOpenError s = fcntl.ioctl(self.fd, TIOCMGET, TIOCM_zero_str) return struct.unpack('I', s)[0] & TIOCM_DSR != 0 @property def ri(self): """Read terminal status line: Ring Indicator""" if not self.is_open: raise portNotOpenError s = fcntl.ioctl(self.fd, TIOCMGET, TIOCM_zero_str) return struct.unpack('I', s)[0] & TIOCM_RI != 0 @property def cd(self): """Read terminal status line: Carrier Detect""" if not self.is_open: raise portNotOpenError s = fcntl.ioctl(self.fd, TIOCMGET, TIOCM_zero_str) return struct.unpack('I', s)[0] & TIOCM_CD != 0 # - - platform specific - - - - @property def out_waiting(self): """Return the number of bytes currently in the output buffer.""" #~ s = fcntl.ioctl(self.fd, termios.FIONREAD, TIOCM_zero_str) s = fcntl.ioctl(self.fd, TIOCOUTQ, TIOCM_zero_str) return struct.unpack('I', s)[0] def fileno(self): """\ For easier use of the serial port instance with select. WARNING: this function is not portable to different platforms! """ if not self.is_open: raise portNotOpenError return self.fd def set_input_flow_control(self, enable=True): """\ Manually control flow - when software flow control is enabled. This will send XON (true) or XOFF (false) to the other device. WARNING: this function is not portable to different platforms! """ if not self.is_open: raise portNotOpenError if enable: termios.tcflow(self.fd, termios.TCION) else: termios.tcflow(self.fd, termios.TCIOFF) def set_output_flow_control(self, enable=True): """\ Manually control flow of outgoing data - when hardware or software flow control is enabled. WARNING: this function is not portable to different platforms! """ if not self.is_open: raise portNotOpenError if enable: termios.tcflow(self.fd, termios.TCOON) else: termios.tcflow(self.fd, termios.TCOOFF) def nonblocking(self): """DEPRECATED - has no use""" import warnings warnings.warn("nonblocking() has no effect, already nonblocking", DeprecationWarning) class PosixPollSerial(Serial): """\ Poll based read implementation. Not all systems support poll properly. However this one has better handling of errors, such as a device disconnecting while it's in use (e.g. USB-serial unplugged). """ def read(self, size=1): """\ Read size bytes from the serial port. If a timeout is set it may return less characters as requested. With no timeout it will block until the requested number of bytes is read. """ if not self.is_open: raise portNotOpenError read = bytearray() poll = select.poll() poll.register(self.fd, select.POLLIN | select.POLLERR | select.POLLHUP | select.POLLNVAL) if size > 0: while len(read) < size: # print "\tread(): size",size, "have", len(read) #debug # wait until device becomes ready to read (or something fails) for fd, event in poll.poll(self._timeout * 1000): if event & (select.POLLERR | select.POLLHUP | select.POLLNVAL): raise SerialException('device reports error (poll)') # we don't care if it is select.POLLIN or timeout, that's # handled below buf = os.read(self.fd, size - len(read)) read.extend(buf) if ((self._timeout is not None and self._timeout >= 0) or (self._inter_byte_timeout is not None and self._inter_byte_timeout > 0)) and not buf: break # early abort on timeout return bytes(read) class VTIMESerial(Serial): """\ Implement timeout using vtime of tty device instead of using select. This means that no inter character timeout can be specified and that the error handling is degraded. Overall timeout is disabled when inter-character timeout is used. """ def _reconfigure_port(self, force_update=True): """Set communication parameters on opened port.""" super(VTIMESerial, self)._reconfigure_port() fcntl.fcntl(self.fd, fcntl.F_SETFL, 0) # clear O_NONBLOCK if self._inter_byte_timeout is not None: vmin = 1 vtime = int(self._inter_byte_timeout * 10) elif self._timeout is None: vmin = 1 vtime = 0 else: vmin = 0 vtime = int(self._timeout * 10) try: orig_attr = termios.tcgetattr(self.fd) iflag, oflag, cflag, lflag, ispeed, ospeed, cc = orig_attr except termios.error as msg: # if a port is nonexistent but has a /dev file, it'll fail here raise serial.SerialException("Could not configure port: {}".format(msg)) if vtime < 0 or vtime > 255: raise ValueError('Invalid vtime: {!r}'.format(vtime)) cc[termios.VTIME] = vtime cc[termios.VMIN] = vmin termios.tcsetattr( self.fd, termios.TCSANOW, [iflag, oflag, cflag, lflag, ispeed, ospeed, cc]) def read(self, size=1): """\ Read size bytes from the serial port. If a timeout is set it may return less characters as requested. With no timeout it will block until the requested number of bytes is read. """ if not self.is_open: raise portNotOpenError read = bytearray() while len(read) < size: buf = os.read(self.fd, size - len(read)) if not buf: break read.extend(buf) return bytes(read) # hack to make hasattr return false cancel_read = property()