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In the ROS2 docs for create_timer(), I don't see any arguments for NOT auto-starting the timer upon creation (unlike the createTimer() function in ROS1)
Am I just not seeing the way to do this in ROS2? Are there any workarounds?
Turns out it is fairly simple:
In your constructor:
// Create the timer
timer_ = this->create_wall_timer(
timer_duration,
std::bind(&MyClass::timer_callback, this));
// Instantly stop the timer
timer_->cancel();
And then define e.g. a service callback to start/stop the timer:
if (start_) {
timer_->reset(); // starts the timer
} else {
timer_->cancel(); // stops the timer
}
It's OK to call cancel() on an already stopped timer.
Well, technically, my answer answers at least one of the questions, whereas you can't is neither an answer to Am I just not seeing the way to do this in ROS2? nor to Are there any workarounds?. ;-)
Re. the proposed workaround: one possible flaw is that the constructor could be preempted between the creation and the cancelling of the timer, so that the timer might fire at least once if the preemption is long enough and the timer period small enough. But I assume this has a neglible probability for the typical use case.
The main question appears to be "How to NOT auto-start timer in ROS2?" (at least, that's the title of the post). The answer to that would be "it's not supported".
Note btw I wasn't trying to imply your answer is wrong. I even upvoted it.
Just pointing out something which seems like it should be documented somewhere.
Recently this functionality has been added rolling: https://github.com/ros2/rclcpp/pull/2005
Asked: 2021-09-26 12:33:01 -0500
Seen: 1,700 times
Last updated: Jun 20 '23
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I have a workaround where I have a
std::shared_ptrmember variable for the timer and only callcreateTimer()when I actually want to start the timer. And to stop the timer from hitting it's callbacks, I simply call.reset()on thestd::shared_ptrmember variable