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429 lines
16 KiB
429 lines
16 KiB
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"""
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Python module implementing the TDW (This Do What #!?) serial message format.
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Currently only supports responses to sent messages, rather than generic RX.
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Intended use:
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>>> msg_handler = tdw.MessageHandler("/dev/ttyAMA0", 57600)
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>>> rqst = msg_handler.send_request("BATV")
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>>> if rqst.wait_for_response()
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>>> print(rqst.response)
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"""
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import sys
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import queue
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import threading
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import serial
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import re
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import time
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from enum import Enum
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DEFAULT = object()
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MAX_MSG_LEN = 128
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MAX_MSG_ARGS = 8
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# Return a Message object, allowing the the caller to check a "sent" flag to see if it's gone through
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# yet. If needs_response was true, enable a "wait_for_response()" function that internally blocks until
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# response is recieved or times out. Returns either None or a Response object.
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# Note that unless a class overrides __bool__(), it will always evaluate to True, allowing "if wait_for_response():"
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# to check if there's a returned message. A ".response" property gets filled after returning too, allowing
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# use of that rather than the caller having to get a reference.
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# Once "wait_for_response()"" returns, the message handler removes it's reference to the message and
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# the response, so the caller can be sure that it won't be changed underneath it.
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# Currently this is all designed only for comms initiated by Python, and doesn't handle responding
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# to communication initiated by the device yet. For that, perhaps supply callback attachments
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# for specific message names as well as a generic one, but by default queue them up and wait
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# for a call to a "process_messages()" function or something - to allow callbacks to be handled
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# in the same main thread. Optionally have a flag when creating the MessageHandler for it to
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# dispatch callbacks in new threads asynchronously (or have individual flags when attaching callbacks
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# perhaps?)
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class MessageType(Enum):
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COMMENT = "#"
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COMMAND = "!"
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REQUEST = "?"
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def __str__(self):
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return str(self.value)
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class Message():
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"""
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Representation of a message to be sent from this device.
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Also used to track the corresponding response from the other device.
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"""
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def __init__(self, msg_type, msg_name, arguments, multipart_args=None):
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if not isinstance(msg_type, MessageType):
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raise TypeError("Argument message_type must be a MessageType")
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self._msg_type = msg_type
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self._msg_name = str(msg_name)
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self._arguments = arguments
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self._multipart_args = multipart_args
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@property
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def msg_type(self):
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return self._msg_type
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@property
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def msg_name(self):
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return self._msg_name
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@property
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def arguments(self):
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return self._arguments
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@property
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def multipart_args(self):
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return self._multipart_args
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class TXMessage(Message):
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"""
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Locks down and stringifies the arguments and multipart arg list into tuples on creation, avoid
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them being changed underneath it once the message is added to the send queue.
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"""
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def __init__(self, msg_type, msg_name, arguments, needs_response, response_timeout, multipart_args=None):
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# Stringify args and put in immutable tuples
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immutable_args = tuple([str(arg) for arg in arguments])
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immutable_multipart_args = None
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if multipart_args is not None:
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immutable_multipart_args = []
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for arglist in multipart_args:
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immutable_multipart_args.append(tuple([str(arg) for arg in arglist]))
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immutable_multipart_args = tuple(immutable_multipart_args)
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super().__init__(msg_type, msg_name, immutable_args, immutable_multipart_args)
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self._needs_response = needs_response
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self._response_timeout = response_timeout
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self._response = None
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# event that is triggered when a matching command response is
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# recieved and the data parsed into ScoutState. ScoutState should
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# only be then read via the lock on it.
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self._responded = threading.Event()
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@property
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def needs_response(self):
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return self._needs_response
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@property
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def response(self):
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return self._response
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def wait_for_response(self):
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if not self._needs_response:
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raise Exception(
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"Can't wait for response on a message that has not set 'needs_response=True'")
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if self._responded.wait(self._response_timeout):
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# Serial thread should have populated self._response by now
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return self.response
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else:
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return False
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class RXMessage(Message):
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def __init__(self, msg_type, msg_name, arguments, is_multipart=False, multipart_count=0):
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super().__init__(msg_type, msg_name, arguments)
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self._multipart_count = multipart_count
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self._is_multipart = is_multipart
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if is_multipart:
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self._multipart_args = []
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@property
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def multipart_count(self):
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"""
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The declared number of message parts.
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//Not// necessarily the number or parts that were actually received.
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For multipart messages that don't declare a count, this is None.
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"""
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return self._multipart_count
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@property
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def is_multipart(self):
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"""
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Returns true if the message was a multi-part message
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"""
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return self._is_multipart
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class MessageHandler():
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def __init__(self, serial_port, baud_rate, response_timeout=0.5, multipart_timeout=0.2, loop_delay=0.01):
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self._tx_message_queue = queue.Queue()
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self._tx_message = None
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self._tx_sent_time = None
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self._rx_message = None
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self._last_rx_time = None
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self._rx_multipart_timeout = multipart_timeout
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# Default, can be overridden by individual messages
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self.response_timeout = response_timeout
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# delay used in serial processing thread between iterations.
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# If zero, the handler will just spin constantly asking if more serial bytes are available
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# (a fcntl.ioctl call). If too large, you lose responsiveness when a new message comes in (when
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# not waiting for a response the loop delay has an event trigger, so new messages get sent immediately)
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# Very large values risk filling the serial buffer before data can be processed.
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# pyserial buffer is apparently 1024 or 4096 bytes, and at 57600 baud 10ms delay would only
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# be 72 bytes.
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self.loop_delay = loop_delay
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self._rx_string = ""
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self.port = serial.Serial()
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self.port.baudrate = baud_rate # 57600
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# Set port to be non-blocking
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self.port.timeout = 0
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self.port.port = serial_port
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# self._re_message_frame = re.compile(r"([#!?])(.+?)[\r\n]")
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self._re_msg_start = re.compile(r"[#!?]")
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self._frame_end_chars = "\r\n"
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self._re_msg_bounds = re.compile(r"[#!?\r\n]")
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# start thread
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self.thread = threading.Thread(target=self._serial_comm_thread, daemon=True)
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self.thread.start()
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def send_message(self, message):
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"""
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Add a message to the queue to be sent
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"""
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if not isinstance(message, TXMessage):
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raise TypeError("'message' argument must be of type TXMessage")
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self._tx_message_queue.put(message)
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def send_comment(self, message_name, arguments=[], needs_response=False, response_timeout=DEFAULT):
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if response_timeout is DEFAULT:
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response_timeout = self.response_timeout
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msg = TXMessage(MessageType.COMMENT, message_name,
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arguments, needs_response, response_timeout)
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self.send_message(msg)
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return msg
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def send_command(self, message_name, arguments=[], needs_response=True, response_timeout=DEFAULT):
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if response_timeout is DEFAULT:
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response_timeout = self.response_timeout
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msg = TXMessage(MessageType.COMMAND, message_name,
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arguments, needs_response, response_timeout)
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self.send_message(msg)
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return msg
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def send_request(self, message_name, arguments=[], needs_response=True, response_timeout=DEFAULT):
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if response_timeout is DEFAULT:
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response_timeout = self.response_timeout
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msg = TXMessage(MessageType.REQUEST, message_name,
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arguments, needs_response, response_timeout)
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self.send_message(msg)
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return msg
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def _send_message(self):
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"""
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Actually send a message pulled from the queue.
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Only called from the serial_comm thread
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"""
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argstr = ""
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if len(self._tx_message.arguments) > 0:
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argstr = ':'+','.join(self._tx_message.arguments)
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send_str = F"{self._tx_message.msg_type}{self._tx_message.msg_name}{argstr}\n"
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self.port.write(send_str.encode('utf-8'))
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self._tx_sent_time = time.time()
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#print(F"TX: {send_str}")
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# Only keep the current message around if we need to track a response
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if not self._tx_message.needs_response:
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self._tx_message = None
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def _find_msg_frame(self):
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"""
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Finds next frame in the _rx_string, trimming any excess.
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Returns true if it found something and needs to be called again,
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intended to be called in a loop.
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"""
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match = self._re_msg_start.search(self._rx_string)
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if match is None:
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# No command start characters anywhere in the string, so ditch it
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self._rx_string = ""
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return False
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# trim anything before start
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if match.start() > 0:
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self._rx_string = self._rx_string[match.start():]
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# Search for next start or end character
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match = self._re_msg_bounds.search(self._rx_string, 1)
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if match is None:
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# No end of frame found
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if len(self._rx_string) > MAX_MSG_LEN:
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# We have a message start, but too many characters after it without an end
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# of frame, so ditch it.
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self._rx_string = ""
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return False
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if match[0] in self._frame_end_chars:
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# Found our frame end
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self._parse_message_text(self._rx_string[:match.start()])
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# Trim out the message we just found and start again
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self._rx_string = self._rx_string[match.end():]
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return True
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else:
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# Found another start character, trim and start again
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self._rx_string = self._rx_string[match.start():]
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return True
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def _parse_message_text(self, msg_str):
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"""
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Parse a recieved message string.
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'msg_str' contains the start character and everything after that,
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not including the terminating linefeed.
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Only called from the serial_comm thread
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"""
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#print(F"RX: {msg_str}")
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self._last_rx_time = time.time()
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msg_name, _, msg_args_text = msg_str.strip(' \t').partition(':')
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# Convert the character to our enum for later comparison
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msg_type = MessageType(msg_name[0])
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msg_name = msg_name[1:]
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msg_args = msg_args_text.split(',')
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# Trim whitespace around name and args
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msg_name = msg_name.strip(' \t')
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msg_args = [arg.strip(' \t') for arg in msg_args]
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multipart_count = None
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multipart_start = False
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multipart_end = False
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if msg_args[-1][0] == '<':
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multipart_start = True
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# Message is indicating a multipart start
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count_txt = msg_args[-1][1:].strip(" \t")
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try:
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multipart_count = int(count_txt)
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except ValueError:
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# If no count supplied or can't understand it, treat it as open
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multipart_count = None
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# Remove the multipart start indicator from the args
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msg_args = msg_args[:-1]
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elif msg_args[-1][0] == '>':
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multipart_end = True
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# Remove the multipart end indicator from the args
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msg_args = msg_args[:-1]
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if self._rx_message is not None:
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# We have a multipart message in progress
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if (self._rx_message.msg_name == msg_name) and (self._rx_message.msg_type == msg_type) and (not multipart_start):
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# Only skip adding args to list if it's a blank mutipart end message
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if not (multipart_end and (len(msg_args) == 0)):
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self._rx_message._multipart_args.append(msg_args)
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if multipart_end or (len(self._rx_message.multipart_args) >= self._rx_message.multipart_count):
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self._process_rx_message()
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# We're done here
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return
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else:
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# We've got a new message interrupting the in-progress one
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# Close off existing rx message and continue
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self._process_rx_message()
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self._rx_message = RXMessage(msg_type, msg_name, msg_args,
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is_multipart=multipart_start, multipart_count=multipart_count)
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if not self._rx_message.is_multipart:
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self._process_rx_message()
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def _process_rx_message(self):
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"""
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Process a received and parsed message in self._rx_message,
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and dispatches any necessary actions.
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Clears self._rx_message after it's done.
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"""
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#print(F"Process rx_msg: {self._rx_message.msg_name}")
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#print(F"tx message during processing is {self._tx_message.msg_name}")
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if (self._tx_message is not None) and (self._tx_message.msg_name == self._rx_message.msg_name) and (self._rx_message.msg_type == MessageType.COMMENT):
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# _tx_message only hangs around if it's waiting for response.
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# can't just assume next received message is a response, as the other
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# device might be sending something else in the meantime, so check for name.
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# Responses are always comments.
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self._tx_message._response = self._rx_message
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self._tx_message._responded.set()
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self._tx_message = None
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else:
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pass
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# TODO - Handle other type of received message and dispatch actions here - callbacks?
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self._rx_message = None
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def _handle_serial_port(self):
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# If there's bytes, read them and deal with them. The underlying port read locks
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# the GIL, so use non-blocking mode.
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if self.port.in_waiting > 0:
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new_bytes = self.port.read(self.port.in_waiting)
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self._rx_string = self._rx_string + new_bytes.decode('utf-8')
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# Find and process message frames
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while self._find_msg_frame():
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pass
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# Loop back to check for more RX characters (the priority)
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return
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if self._rx_message is not None:
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if (time.time()-self._last_rx_time) >= self._rx_multipart_timeout:
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# Been too long waiting for a multipart message part, timeout and process
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# so the main program can use the message
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self._process_rx_message()
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if self._tx_message is not None:
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# Wait for current tx_message to time out
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if (time.time()-self._tx_sent_time) >= self._tx_message._response_timeout:
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# Timeout the request
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self._tx_message = None
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else:
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time.sleep(self.loop_delay)
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else:
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# Try and get a new message to send
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try:
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self._tx_message = self._tx_message_queue.get(
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block=True, timeout=self.loop_delay)
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# Only gets here if current_tx_message is actually set
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self._send_message()
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except queue.Empty:
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pass
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def _serial_comm_thread(self):
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while True:
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# Actual wait is on either the non-empty queue or a serial character to parse
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# Serial comms is not synchronous, so need to be available to recieve characters
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# at any point
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try:
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self.port.open()
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while True:
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self._handle_serial_port()
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except serial.SerialException:
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time.sleep(1)
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# If there's a serialexception, try to reopen the port
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