Source code for can.broadcastmanager

# coding: utf-8

Exposes several methods for transmitting cyclic messages.

The main entry point to these classes should be through

import abc
import logging
import threading
import time
import warnings

log = logging.getLogger('can.bcm')

[docs]class CyclicTask(object): """ Abstract Base for all cyclic tasks. """
[docs] @abc.abstractmethod def stop(self): """Cancel this periodic task. :raises can.CanError: If stop is called on an already stopped task. """
[docs]class CyclicSendTaskABC(CyclicTask): """ Message send task with defined period """ def __init__(self, message, period): """ :param can.Message message: The message to be sent periodically. :param float period: The rate in seconds at which to send the message. """ self.message = message self.can_id = message.arbitration_id self.arbitration_id = message.arbitration_id self.period = period super(CyclicSendTaskABC, self).__init__()
[docs]class LimitedDurationCyclicSendTaskABC(CyclicSendTaskABC): def __init__(self, message, period, duration): """Message send task with a defined duration and period. :param can.Message message: The message to be sent periodically. :param float period: The rate in seconds at which to send the message. :param float duration: The duration to keep sending this message at given rate. """ super(LimitedDurationCyclicSendTaskABC, self).__init__(message, period) self.duration = duration
[docs]class RestartableCyclicTaskABC(CyclicSendTaskABC): """Adds support for restarting a stopped cyclic task"""
[docs] @abc.abstractmethod def start(self): """Restart a stopped periodic task. """
[docs]class ModifiableCyclicTaskABC(CyclicSendTaskABC): """Adds support for modifying a periodic message"""
[docs] def modify_data(self, message): """Update the contents of this periodically sent message without altering the timing. :param can.Message message: The message with the new :attr:``. Note: The arbitration ID cannot be changed. """ self.message = message
[docs]class MultiRateCyclicSendTaskABC(CyclicSendTaskABC): """Exposes more of the full power of the TX_SETUP opcode. """ def __init__(self, channel, message, count, initial_period, subsequent_period): """ Transmits a message `count` times at `initial_period` then continues to transmit message at `subsequent_period`. :param can.interface.Bus channel: :param can.Message message: :param int count: :param float initial_period: :param float subsequent_period: """ super(MultiRateCyclicSendTaskABC, self).__init__(channel, message, subsequent_period)
class ThreadBasedCyclicSendTask(ModifiableCyclicTaskABC, LimitedDurationCyclicSendTaskABC, RestartableCyclicTaskABC): """Fallback cyclic send task using thread.""" def __init__(self, bus, lock, message, period, duration=None): super(ThreadBasedCyclicSendTask, self).__init__(message, period, duration) self.bus = bus self.lock = lock self.stopped = True self.thread = None self.end_time = time.time() + duration if duration else None self.start() def stop(self): self.stopped = True def start(self): self.stopped = False if self.thread is None or not self.thread.is_alive(): name = "Cyclic send task for 0x%X" % (self.message.arbitration_id) self.thread = threading.Thread(target=self._run, name=name) self.thread.daemon = True self.thread.start() def _run(self): while not self.stopped: # Prevent calling bus.send from multiple threads with self.lock: started = time.time() try: self.bus.send(self.message) except Exception as exc: log.exception(exc) break if self.end_time is not None and time.time() >= self.end_time: break # Compensate for the time it takes to send the message delay = self.period - (time.time() - started) time.sleep(max(0.0, delay))
[docs]def send_periodic(bus, message, period, *args, **kwargs): """ Send a :class:`~can.Message` every `period` seconds on the given bus. :param can.BusABC bus: A CAN bus which supports sending. :param can.Message message: Message to send periodically. :param float period: The minimum time between sending messages. :return: A started task instance """ warnings.warn("The function `can.send_periodic` is deprecated and will " + "be removed in an upcoming version. Please use `can.Bus.send_periodic` instead.", DeprecationWarning) return bus.send_periodic(message, period, *args, **kwargs)