Consistent robot flicker every 64 seconds

[E Dawg]

I concur with the above. Go through your code and make sure that there are no overflow warnings (hopefully WindRiver alerts you to that).

[MamaSpoldi]

Check the NetConsole output. There could be helpful messages being printed there that could point you in the right direction.

[William Kunkel]

Sorry for not responding quickly. We're using C++, and I'm compiling with -Wall -pedantic -Wextra and not getting any warnings or errors. I agree that it's probably an overflow error of some sort, but 64 seconds seemed like such a specific number that I was hoping it might be something in WPILib. There is no output over netconsole. Looking at the DS Log Viewer, there seem to be spikes in dropped packets that correspond to the flickering.

[PandaHatMan]

Where is your D-Link on your robot? Is it close to any noisy circuits?

[William Kunkel]

Our D-link is pretty isolated. I don't think it's the problem.

[Greg McKaskle]

Does the 64 seconds hiccup go away when disabled, if you stay in auto for 64 seconds, or in teleOp. If not, then what of your code is running in all of those cases? Start disabling things a chunk at a time. Use your intuition as to what is more likely to be responsible, but if you have no guess, just use binary search approach. Carefully take half your subsystems out of the system. Did the problem belong to the ones that remain or the ones you took out. Iterate on the right half until you identify it.

Do this in an experimental branch of your code, don't submit things or lose work doing this, but this type of debugging exposition is a very valuable skill in all forms of engineering.

Even if the issue is in WPILib, it may well be due to how your team is using it, and this narrowing of the root cause will be helpful to the people who will debug it. But there is a good chance that you will discover the bug yourself if you take this approach.

Greg McKaskle

[PhilBot]

Hi

I just posted a similar issue and got pointed here.

See my post:
http://www.chiefdelphi.com/forums/sh...d.php?t=127469

I've pretty much determined that it's related to the PC running the driver station. It's a new HP convertible laptop running Windows 8. My other personal Windows 8 laptop does NOT exhibit the problem.

What laptop are you using, and have you tried a different one?

Phil.

[MrRoboSteve]

Wifi or wired? Works on one but not the other?

Network drivers fully up to date?

Any difference in antivirus/malware software on working/failing machine?

If you plot these performance counters in perfmon:

\Network Adapter(x)\Output Queue Length
\Network Adapter(x)\Packets Outbound Discarded
\Network Adapter(x)\Packets Outbound Errors

where x is the network adapter you are using, do you see anything unusual? Perfmon instructions at http://technet.microsoft.com/en-us/l.../cc749115.aspx

[PhilBot]

The DS is wireless to the router.

I'll check the other things on Thursday when I get access to the prototype robot.

[MrRoboSteve]

Some more ideas.

Look in the Event Viewer and see if there are unusual events related to the networking stack.

They'd usually be under Event Viewer -> Custom Views -> Administrative Events in the tree view.

I'd also go look at the manufacturer web site to see whether there is a new network driver.

Can you repro the issue without any of the FRC software in the loop? One easy way to see would be to copy a very large file to a share on another machine, by dragging in File Explorer. win8 has a very nice visualization of the copy throughput that should clearly show if you're getting blocked periodically.

[Greg McKaskle]

Phil. I sent a PM with some ideas. Let me know.

Greg McKaskle

[PhilBot]

Hi All.

Well, I narrowed down the symptoms even if I don't know the cause. The periodic glitch only occurs when the DS is connected to the router wirelessly.

That is, if I have the DS computer hardwired to a wireless router (with the DS wireless disabled), and the robot is connected to the same router wirelessly, there is no periodic hiccup.

However if the DS connects to the same router wirelessly (no hard wire) I get the periodic hiccup. I tried two different routers (one old and one really new) and I get the identical effect.

I was wondering if the computer was having a hard time because the Robot wireless network does not have access to the internet, and it's doing something to test the connection once a minute.

The good news is that this shouldn't be an issue during competition.... right