This is a snippet of python used to read incoming LLAP messages from a serial port, is called as part of a while loop in a dedicated serial thread.

PythonLLAPSerialin.py

   # class level varables for check incoming characters are valid LLAP
    _validID = "ABCDEFGHIJKLMNOPQRSTUVWXYZ-#@?\\*"
    _validData = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 !\"#$%&'()*+,-.:;<=>?@[\\\/]^_`{|}~"


    def _SerialReadIncomingLLap(self):
        char = self._serial.read()  # should not time out but we should check anyway
        self.logger.debug("tSerial: RX:{}".format(char))
    
        if char == 'a':
            # this should be the start of a llap message
            # read 11 more or time out
            llapMsg = "a"
            count = 0
            while count < 11:
                char = self._serial.read()
                if not char:
                    self.logger.debug("tSerial: RX:{}".format(char))
                    return
            
                if char == 'a':
                    # start again and
                    count = 0
                    llapMsg = "a"
                    self.logger.debug("tSerial: RX:{}".format(char))
                elif (count == 0 or count == 1) and char in self._validID:
                    # we have a vlaid ID
                    llapMsg += char
                    count += 1
                elif count >= 2 and char in self._validData:
                    # we have a valid data
                    llapMsg += char
                    count +=1
                else:
                    self.logger.debug("tSerial: RX:{}".format(llapMsg[1:] + char))
                    return
    
            self.logger.debug("tSerial: RX:{}".format(llapMsg[1:]))
            
            if len(llapMsg) == 12:  # just double check length
                if llapMsg[1:3] == "??":
                    self._SerialProcessQQ(llapMsg[3:].strip("-"))
                else:
                    # not a configme llap so send out via UDP LLAP
                    try:
                        self.qUDPSend.put_nowait(self.encodeLLAPJson(llapMsg, self.config.get('Serial', 'network')))
                    except Queue.Full:
                        self.logger.warn("tSerial: Failed to put {} on qUDPSend as it's full".format(llapMsg))