LabView Programming - Do we still need Watchdog?

[wazcodez]

Originally Posted by Mark McLeod

I take it back...
I re-checked my notes and I misremembered one part.

This is what happens when a Safety vi trips.

The status on the Driver Station remains "Autonomous Enabled" or whatever field mode we're in.
The Diagnostics Message Window shows this error message each time it happens:

ERROR <Code> -44061 occurred at "Left and Right Motors" in the VI path: Robot Main.vi
<time>23:15:45 01/21/2011
FRC:  The loop that contains RobotDrive is not running fast enough. 
This error can occur if the loop contains too much code, or if one or 
more other loops are starving the RobotDrive loop.

If you have an autonomous that makes several drive moves then it will:

1. do the first drive move for .1 second
2. stop and display the error above
3. do the second drive move for .1 second
4. stop and display the error above
5. etc.

If you have a bunch of moves close together you'll think the cRIO is pulsing.

How do you fix it ?

[Mark McLeod]

To fix it, you should analyze your code to really understand if you've got slow code that needs to be sped up. If your code really is laggy then it'll be sluggish in responding to the driver controls even without the Safety vi and it must be fixed.

There's a drop-in tool NI included with the framework this year called Elapsed Times.vi
You'll find it in your project under the Support Code folder.
Just drop it into teleop.vi, Run the project from Robot Main.vi, and bring up the Elapsed Times.vi front panel to watch how long everything takes.

If it's just a coding style that's the problem, then the Safety vi can be turned off.
Inside Open 2/4 Motor (used in Begin.vi) there is an enable/disable.

[Greg McKaskle]

The LV team fully intended to come up with a good replacement for the Delay and Feed VI. Since it never managed to be completed, I'll relate the concept.The idea is to save a copy of Delay and Feed and create a Delay and Update. One step inside the Robot Drive VIs, you'll find a call to Safety Update. You don't need to wire values or anything except the refnum for RobotDrive. Add the appropriate refnums to the connector. If the correct updates are called in place of the Feed of the old VI, I believe the piecewise autonomous will work as before, and I believe that pausing a VI or hitting a breakpoint will typically halt the robot. I say typically because unlike the watchdog, it is possible to pause some of the lower level safety VIs and bypass the safety. This shouldn't happen unless someone is way off the mark in their debugging.

Since I haven't implemented this, and certainly haven't tested it, please test the breakpoint in auto carefully before trusting it.

Greg McKaskle