Create3 docs show bot killer echo /tf, should show tf2_echo with repetition rate

[slowrunner]

See final comment in discussion thread for suggestion

Discussed in #496

^{Originally posted by atinfinity December 22, 2023}

How are you connecting to your Create 3?

USB Ethernet (ROS 2)

Computer(s) Model(s) and Operating System(s)

No response

Which version of ROS 2 is installed on your computer?

Humble

Which firmware version is installed on your robot?

H.2.3

Which RMW is your robot running?

FastRTPS

Does your robot have an assigned namespace? If so, please share.

No response

Is the robot connected to a network? If so, what is the network type?

No response

Are there multiple Create 3 robots connected to your network?

None

Is multicast enabled?

None

What is the Adapter Board's USB/BLE Toggle currently switched to?

None

Describe your question.

I encountered this problem(turtlebot/turtlebot4#152).
And, I found the following description in this ticket .

The issue is being tracked here.

#381 is reported in Create 3. I checked that CPU usage of Create 3 is very high.
But, this ticket has no updates. Is this a problem of Create 3's firmware?
I think iRobot should clarify this issue.

[alsora]

I think that this recommendation is not correct.
Using tf2_echo requires the create 3 to do more work than just doing ros2 topic echo /tf.

I saw your data in the other thread, but correlation is not causation.
I provided details here about why tf2_echo shouldn't be used as an alternative to /tf to reduce CPU usage on the robot: #496 (reply in thread)

Moreover, the numeric arguments that you add at the end

ros2 run tf2_ros tf2_echo odom base_link 0.1

is the frequency at which your laptop will check if the tree is valid and the transformation is available.
This will check the local cache, i.e. the transformations that you already received from the robot, and it won't have any impact on the work done by the robot.

The /tf topic has nothing special.
Subscribing to it won't cause more load to the robot than subscribing to any other topic with the same publish frequency.
The CPU spike on the robot is not caused by tf alone, but rather it's likely a combination of multiple factors.

[slowrunner]

Understand better, thanks.