Intermittent WiFi Communication Issues

[david.e.boles]

Update and questions on 5940's practice robot build:

We did additional troubleshooting today and were able to get WiFi based communication working intermittently after messing with the router settings and switching out the Ethernet cable on the robot. The cable we had been using was tested by another team-mate later but seemed to be fine. In any case we're pretty stumped on what the problem might be, there doesn't seem to be a pattern. Do you guys have any ideas?

[Jeremy Germita]

What band have you configured your AP to use? There tends to be a lot of interference on the 2.4GHz channels. This can often cause intermittent connection and high ping times if your access point is also in the 2.4GHz range.

If you have access to an Android device, I highly recommend downloading the app WiFi Analyzer(I haven't quite checked to see if there is an alternative for iOS). You can view wireless channel usage around the phone. Very useful for debugging wireless issues. If your robot AP is sharing a channel with other APs in the area, I recommend finding the least populated channel and setting your AP to use that.

The 5GHz band is usually a lot cleaner, so if you have access to a 5GHz capable computer for your driver station, you will probably see improved connection performance.

On the hardware side of things, I recommend checking all electrical connections that power the AP and the roborio. Does your robot lose connection while standing still or does it have to move before losing comms? If the latter, I'd bet on a faulty electrical connection being the culprit.

[david.e.boles]

We managed to drive it around at full speed fine when we got it to connect, but when we restarted the robot it was not discovered. We'll try out the 5ghz thing, our school does have a lot of overlapping AP coverage... Thanks!

[david.e.boles]

I have non idea why, but everything works fine if we start Driver Station while windows says it's connecting to the network. If you open it after it doesn't, if you open then, close and reopen it still works! WT*!!! Anyway, seems to be usable, just weird. Anything we're missing?

[rich2202]

Seems like your driver station is connecting to the school's network when the robot is not on (broadcasting an ssid). We set up our driver station network connections so: robot ssid is auto connect, and the school's ssid is manual connect only. That way, when the robot is rebooting, it doesn't try to connect to the school's network and waits to find the robot's network.

If you can't find that setting, then you will have to manually tell the ds to switch to the robot network. FYI: when not driving (testing non driving functions) we teather to speed up the process and not worry about wifi.

[david.e.boles]

It's not the computer that Driver Station is running on, it's when you open the program itself... (It definitely doesn't work when connected to the robot, after windows says it has finished connecting to the robot, unless driver station was opened then closed while it was connecting) I can upload a video if unclear. I am running windows 10 but I'm pretty sure we had the same issue on windows 8; I'll double check.

[rich2202]

Originally Posted by david.e.boles

I can upload a video if unclear.

Upload a video.

You have 2 levels of communication that need to be established.

1) Windows (the Operating System) needs to connect the Wifi device on the laptop with the Router (Dlink) on the Robot. That establishes the path for all the network traffic.

2) The Driver Station Program uses the network to establish a connection between the DS Program and the Robo Rio program (and any other recognized devices, such as the USB Camera). This is like you browser (IE, FF, Chrome) connecting to a website (Chiefdelphi.com).

#2 cannot happen until after #1 happens. #1 will happen automatically when the laptop first starts up. It also happens when it looses a connection, and tries to find another.

You will loose #1 every time the robot is power cycled (the Dlink resets). If the Dlink is on (robot is on) when the laptop is booting, it may find the robot as the first network it tries to connect to. If the dlink is not there, it may try to contact to the School's wifi network. That is what you want to prevent so the laptop will keep looking for the dlink until it finds it.

You can tell #1 is happening when you see the little wifi icon on the bottom right of the screen. You can also use those icons to see which wifi network you are connected.

You can see #2 happening in one of the DS status windows.

If #1 happens and it connects to the School's wifi, you will never connect to the dlink until you reset the wifi interface on your laptop. There are numerous ways to do that, including rebooting the laptop.

Are you are saying that the following works (Scenario A):
1) Computer boots
2) As soon you can, you launch the DS program
3) #1 happens (windows connecting) to the dlink while the DS program is loading.

And that the following does not work (Scenario B):
1) Computer boots
2) #1 happens and connects to the dlink (not the school's wifi)
3) After #1 is completed, launch the DS.

As long as you are connecting to the dlink, Scenario B should always work.