Python termios.PARENB Examples

def __init__(self, device="/dev/ttyAMA0", baudrate=9600):
        if not device.startswith("/dev/"):
            device = "/dev/%s" % device
        
        if isinstance(baudrate, str):
            baudrate = int(baudrate)

        aname = "B%d" % baudrate
        if not hasattr(termios, aname):
            raise Exception("Unsupported baudrate")
        self.baudrate = baudrate

        Bus.__init__(self, "UART", device, os.O_RDWR | os.O_NOCTTY)
        fcntl.fcntl(self.fd, fcntl.F_SETFL, os.O_NDELAY)
        
        #backup  = termios.tcgetattr(self.fd)
        options = termios.tcgetattr(self.fd)
        # iflag
        options[0] = 0

        # oflag
        options[1] = 0

        # cflag
        options[2] |= (termios.CLOCAL | termios.CREAD)
        options[2] &= ~termios.PARENB
        options[2] &= ~termios.CSTOPB
        options[2] &= ~termios.CSIZE
        options[2] |= termios.CS8

        # lflag
        options[3] = 0

        speed = getattr(termios, aname)
        # input speed
        options[4] = speed
        # output speed
        options[5] = speed
        
        termios.tcsetattr(self.fd, termios.TCSADRAIN, options) 

def _get_parity(self):
        # Get tty attributes
        try:
            (_, _, cflag, _, _, _, _) = termios.tcgetattr(self._fd)
        except termios.error as e:
            raise SerialError(e.errno, "Getting serial port attributes: " + e.strerror)

        if (cflag & termios.PARENB) == 0:
            return "none"
        elif (cflag & termios.PARODD) == 0:
            return "even"
        else:
            return "odd" 

def _set_parity(self, parity):
        if not isinstance(parity, str):
            raise TypeError("Invalid parity type, should be string.")
        elif parity.lower() not in ["none", "even", "odd"]:
            raise ValueError("Invalid parity, can be: \"none\", \"even\", \"odd\".")

        parity = parity.lower()

        # Get tty attributes
        try:
            (iflag, oflag, cflag, lflag, ispeed, ospeed, cc) = termios.tcgetattr(self._fd)
        except termios.error as e:
            raise SerialError(e.errno, "Getting serial port attributes: " + e.strerror)

        # Modify tty attributes
        iflag &= ~(termios.INPCK | termios.ISTRIP)
        cflag &= ~(termios.PARENB | termios.PARODD)
        if parity != "none":
            iflag |= (termios.INPCK | termios.ISTRIP)
            cflag |= termios.PARENB
        if parity == "odd":
            cflag |= termios.PARODD

        # Set tty attributes
        try:
            termios.tcsetattr(self._fd, termios.TCSANOW, [iflag, oflag, cflag, lflag, ispeed, ospeed, cc])
        except termios.error as e:
            raise SerialError(e.errno, "Setting serial port attributes: " + e.strerror) 

def __init__(self, printer, prot, iomanager):
    self.printer = printer
    self.prot = prot
    self.iomanager = iomanager

    (master_fd, slave_fd) = os.openpty()
    slave = os.ttyname(slave_fd)

    master_flags = fcntl.fcntl(master_fd, fcntl.F_GETFL, 0)
    fcntl.fcntl(master_fd, fcntl.F_SETFL, master_flags | os.O_NONBLOCK)

    # switch to "raw" mode - these constants come from the manpage for termios under cfmakeraw()
    master_attr = termios.tcgetattr(master_fd)
    master_attr[0] &= ~(termios.IGNBRK | termios.BRKINT | termios.PARMRK | termios.ISTRIP
                        | termios.INLCR | termios.IGNCR | termios.ICRNL | termios.IXON)
    master_attr[1] &= ~termios.OPOST
    master_attr[2] &= ~(termios.CSIZE | termios.PARENB)
    master_attr[3] &= ~(termios.ECHO | termios.ECHONL | termios.ICANON | termios.ISIG
                        | termios.IEXTEN)
    master_attr[3] |= termios.CS8
    termios.tcsetattr(master_fd, termios.TCSADRAIN, master_attr)

    # Fun detail: master will always show as /dev/ptmx, but the kernel knows from
    # the fd which PTY we're using. This means we have to use master_fd instead
    # of opening master by name.

    logging.info("Opened PTY for {} and got {}".format(prot, os.ttyname(slave_fd)))

    self.pipe_link = "/dev/" + prot + "_1"

    try:
      os.unlink(self.pipe_link)
    except OSError as e:
      # file not found is fine to ignore - anythine else and we should log it
      if e.errno != errno.ENOENT:
        logging.error("Failed to unlink '{}': {}".format(self.pipe_link, e.strerror))

    logging.info("linking {}".format(self.pipe_link))
    os.symlink(slave, self.pipe_link)
    os.chmod(self.pipe_link, 0o666)

    logging.info("{} Pipe open. Use '{}' to communicate with it".format(self.prot, self.pipe_link))

    self.rd = os.fdopen(master_fd, "r")
    self.wr = os.fdopen(master_fd, "w")

    self.send_response = True
    self.iomanager.add_file(self.rd, self.get_message)