network.PeriodicTask.update fails to update periodic RPDO

[dominjon]

I believe I've found a bug when attempting to update a periodic RPDO whose values I'm setting.

The logic of network.PeriodicTask.update attempts to check if the data are new by checking the argument it's been passed against the existing value in the pdo.Map. However, pdo.Map.update is passing network.PeriodicTask.update the same value. If the task does not have the modify_data attribute, then the fact that new_data != old_data is trivially false means that the data are never updated.

[erlend-aasland]

The new data is saved to .msg.data, no matter which branch is taken:

canopen/canopen/network.py

Lines 327 to 335 in a196e1e

	new_data = bytearray(data)
	old_data = self.msg.data
	self.msg.data = new_data
	if hasattr(self._task, "modify_data"):
	self._task.modify_data(self.msg)
	elif new_data != old_data:
	# Stop and start (will mess up period unfortunately)
	self._task.stop()
	self._start()

AFAICS, modify_data is only used to update the task without affecting the timing (see the python-can source). If modify_data is not available, the workaround is to restart the task, thus affecting the timing for the subsequent task execution.

Do you have a code snippet to reproduce the failure you're seeing?