The broadcast manager allows the user to setup periodic message jobs. For example sending a particular message at a given period. The broadcast manager supported natively by several interfaces and a software thread based scheduler is used as a fallback.

This example shows the socketcan backend using the broadcast manager:

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 #!/usr/bin/env python # coding: utf-8 """ This example exercises the periodic sending capabilities. Expects a vcan0 interface: python3 -m examples.cyclic """ from __future__ import print_function import logging import time import can logging.basicConfig(level=logging.INFO) def simple_periodic_send(bus): """ Sends a message every 20ms with no explicit timeout Sleeps for 2 seconds then stops the task. """ print("Starting to send a message every 200ms for 2s") msg = can.Message(arbitration_id=0x123, data=[1, 2, 3, 4, 5, 6], extended_id=False) task = bus.send_periodic(msg, 0.20) assert isinstance(task, can.CyclicSendTaskABC) time.sleep(2) task.stop() print("stopped cyclic send") def limited_periodic_send(bus): print("Starting to send a message every 200ms for 1s") msg = can.Message(arbitration_id=0x12345678, data=[0, 0, 0, 0, 0, 0], extended_id=True) task = bus.send_periodic(msg, 0.20, 1, store_task=False) if not isinstance(task, can.LimitedDurationCyclicSendTaskABC): print("This interface doesn't seem to support a ") task.stop() return time.sleep(2) print("Cyclic send should have stopped as duration expired") # Note the (finished) task will still be tracked by the Bus # unless we pass store_task=False to bus.send_periodic # alternatively calling stop removes the task from the bus #task.stop() def test_periodic_send_with_modifying_data(bus): print("Starting to send a message every 200ms. Initial data is ones") msg = can.Message(arbitration_id=0x0cf02200, data=[1, 1, 1, 1]) task = bus.send_periodic(msg, 0.20) if not isinstance(task, can.ModifiableCyclicTaskABC): print("This interface doesn't seem to support modification") task.stop() return time.sleep(2) print("Changing data of running task to begin with 99") msg.data[0] = 0x99 task.modify_data(msg) time.sleep(2) task.stop() print("stopped cyclic send") print("Changing data of stopped task to single ff byte") msg.data = bytearray([0xff]) msg.dlc = 1 task.modify_data(msg) time.sleep(1) print("starting again") task.start() time.sleep(1) task.stop() print("done") # Will have to consider how to expose items like this. The socketcan # interfaces will continue to support it... but the top level api won't. # def test_dual_rate_periodic_send(): # """Send a message 10 times at 1ms intervals, then continue to send every 500ms""" # msg = can.Message(arbitration_id=0x123, data=[0, 1, 2, 3, 4, 5]) # print("Creating cyclic task to send message 10 times at 1ms, then every 500ms") # task = can.interface.MultiRateCyclicSendTask('vcan0', msg, 10, 0.001, 0.50) # time.sleep(2) # # print("Changing data[0] = 0x42") # msg.data[0] = 0x42 # task.modify_data(msg) # time.sleep(2) # # task.stop() # print("stopped cyclic send") # # time.sleep(2) # # task.start() # print("starting again") # time.sleep(2) # task.stop() # print("done") if __name__ == "__main__": reset_msg = can.Message(arbitration_id=0x00, data=[0, 0, 0, 0, 0, 0], extended_id=False) for interface, channel in [ ('socketcan', 'vcan0'), #('ixxat', 0) ]: print("Carrying out cyclic tests with {} interface".format(interface)) bus = can.Bus(interface=interface, channel=channel, bitrate=500000) bus.send(reset_msg) simple_periodic_send(bus) bus.send(reset_msg) limited_periodic_send(bus) test_periodic_send_with_modifying_data(bus) #print("Carrying out multirate cyclic test for {} interface".format(interface)) #can.rc['interface'] = interface #test_dual_rate_periodic_send() bus.shutdown() time.sleep(2) 

The class based api for the broadcast manager uses a series of mixin classes. All mixins inherit from CyclicSendTaskABC which inherits from CyclicTask.

class can.broadcastmanager.CyclicTask[source]

Bases: object

Abstract Base for all cyclic tasks.

stop()[source]

Raises: can.CanError – If stop is called on an already stopped task.
class can.broadcastmanager.CyclicSendTaskABC(message, period)[source]

Message send task with defined period

Parameters: message (can.Message) – The message to be sent periodically. period (float) – The rate in seconds at which to send the message.
class can.broadcastmanager.LimitedDurationCyclicSendTaskABC(message, period, duration)[source]

Message send task with a defined duration and period.

Parameters: message (can.Message) – The message to be sent periodically. period (float) – The rate in seconds at which to send the message. duration (float) – The duration to keep sending this message at given rate.
class can.broadcastmanager.MultiRateCyclicSendTaskABC(channel, message, count, initial_period, subsequent_period)[source]

Exposes more of the full power of the TX_SETUP opcode.

Transmits a message count times at initial_period then continues to transmit message at subsequent_period.

Parameters: channel (can.interface.Bus) – message (can.Message) – count (int) – initial_period (float) – subsequent_period (float) –
class can.ModifiableCyclicTaskABC(message, period)[source]

Adds support for modifying a periodic message

Parameters: message (can.Message) – The message to be sent periodically. period (float) – The rate in seconds at which to send the message.
modify_data(message)[source]

Update the contents of this periodically sent message without altering the timing.

Parameters: message (can.Message) – The message with the new can.Message.data. Note: The arbitration ID cannot be changed.
class can.RestartableCyclicTaskABC(message, period)[source]

Parameters: message (can.Message) – The message to be sent periodically. period (float) – The rate in seconds at which to send the message.
start()[source]

The functional API in can.broadcastmanager.send_periodic() is now deprecated and will be removed in version 4.0. Use the object oriented API via can.BusABC.send_periodic() instead.
can.broadcastmanager.send_periodic(bus, message, period, *args, **kwargs)[source]
Send a Message every period seconds on the given bus.