Control System Network Settings Conundrum

Technical Control System
1

We have found out some problems and contradictions in the control system network in general. I’d like to set the record straight for how it’s really supposed to be set up. Can you help us out?

First of all and long story short, we’ve been trying to connect to the router wirelessly. It’s really helpful because you don’t have to be tethered to it and indirectly a wall socket to power the router. Then your battery powered development computer and battery powered driver station can be used anywhere when connecting to the robot. This is possible because we’ve heard so, plus it has worked a little bit for us in the past and there are even instructions (in the Getting Started control system manual, 2).

One of our student members is an IT techie and with his help we got it working. We set up the wireless network settings on our computers to work with the router. These are basically the same as the wired settings. It worked ok, but we started getting problems and bugs and the whole thing wasn’t perfect since it was done manually. One of the biggest problems was that it wasn’t how FIRST tells us to set it up, so we didn’t know if it would conflict when we went to competitions.

Here’s the contradiction that we think is the issue:
The subnet masks of the different devices needed to be set a certain way, but the FIRST manuals were telling us differently. Our IT techie set them all to 255.255.255.0 (here on referred to as “having one zero/0” since that’s easier and faster to say. That’s the way we’ve said it for simplicity). This is so that they match up with the router subnet mask, which is the same. However, FIRST tells us to set them all to 255.0.0.0 (“having 3 zeroes/0s”). The deal is that you can’t do this for the router because you select the subnet mask from a drop-down list. A 3 zero subnet mask is not an option. FIRST even tells us in the Getting Started manual to use the option with one zero and set everything else to 3 zeros.

So I researched the whole deal, went through the Getting Started manual, found what all the network settings should be for all the devices (IP address, subnet mask, etc), and reset it all back to normal the way FIRST tells us to. I put all this related information in the attached Word document. Then I tried using the instructions they give to set up wireless Classmate-router communication.

We tried it out on the robot. Wireless connection to the router did not work, so we switch to wired, which did. So we have been using wired until we figure this out.

So…
Can anyone explain the subnet mask contradiction? How should the whole thing really be set up? How can we connect to the router successfully?
I have a basic idea of IP addresses and subnet masks after working on the team as a committed programmer and working through all of this. However I don’t know much conceptually, which is exemplified by when I looked up subnet masks on Wikipedia and was swamped with technical terms. :slight_smile: So bear with me if I don’t understand everything.

Feel free to use my document for your own uses and for understanding this issue. We haven’t used it much on our team since we just made it, but I’d expect it to be a lot better than hunting down the information. We’ll use it to help remember what to set our computers back to after we hook them up to the internet, which requires one to set the network settings to “obtain and IP address automatically.”

Thanks for any and all of your help!!!

Network Settings for FRC Control System.doc (24.5 KB)


Network Settings for FRC Control System.doc (24.5 KB)

2

You are not the first one to notice this difference. Although it is not a traditional configuration, 255.0.0.0 will work. Using this subnet mask will also allow the plethora of team numbers used in competition to work without problems.

Now, technically speaking, 10.x.x.x is a Class A address and the classic subnet mask for a Class A address scheme is 255.0.0.0.
A classic subnet mask for a Class C network is 255.255.255.0. When working at your home facility, triple 255.0 is perfectly fine. While at any competition you will want to use the 255.0.0.0.
So, just to make it simpler and easier to not forget to change the subnet mask, use the 255.0.0.0 all the time and you should have few if any problems.

BTW, the classmate PC only can use 803.11g. So, if you are using it in a wireless configuration, make sure you account for that in your configurations.

3

Thanks for your reply (and a quick one at that. don’t you just love CD for that? :smiley: )

Thanks, that’s helpful and makes sense. I would agree to keep it the same all the time. Thanks for the tip too about the wireless speed.

But still, why weren’t we able to get it working (perfectly) with both 255.255.255.0 and 255.0.0.0 + FIRST’s instructions?

4

Perhaps unrelated, but we were unable to use NetBeans on Ubuntu with the 255.255.255.0 subnet mask. Once that was changed to 255.0.0.0, NetBeans suddenly started working.

5

Actually, from your description it sounds like you did get the subnet mask working. The subnet mask is no different on a wireless than on a wired connection and you got your wired connection working you said.

If there’s a difference between your wired and wireless behavior, especially if the wireless cuts in and out, then look at the pure wireless settings, e.g., channel, frequency(2.5ghz/5ghz), bands (b/g/n).
Wireless flakeyness is often due to channel, frequence, or band conflicts with existing wireless devices and networks, especially if you enable DHCP on your router. DHCP lets the router hand out addresses to any random device that wanders by. We had some iTouch automatically connect and claim the Driver Station IP, because the router was mis-set to hand out addresses starting at .1

6

Well, our connection wasn’t intermittent when we tried to set wireless up manually. Sometimes it just wouldn’t work when we hooked it up and we had to go back in and mess with stuff to make it happen. When I tried it with FIRST’s instructions, it would simply connect to the router but not to the robot (connection light on DS was not lit). Could that still be a DHCP issue with our router? How could we switch that off?

EDIT: I looked in the Getting Started manual at some of the images of the router setup “web pages.” There are settings for a DHCP Server in the Basic Setup tab (this is page 50). It is enabled by default. However, you are instructed to set the start address sufix to 10, so since that’s significant it must be used. That makes it sound like you can’t just disable it. However (again :wink: ) from the info in Mark’s post, I would interpret this setting to mean that it gives out addresses starting with 10, which is above anything that is used in the control system. So then it wouldn’t conflict and ultimately I’m headed down a dead end with this, right??

7

Since the router is not used at competition, you can really do whatever you want to it at home.

The Bridge on the robot gets completely reset at competition (and won’t work with the router wirelessly there in any case), and the Classmate resets it’s network connection everytime we start the Driver Station too, so as far as FIRST is concerned that portion of the Getting Started Manual is just a home aid.:slight_smile:

The main use for setting it up at home is to make sure the Bridge works correctly over wireless, before you get to competition and find it’s broken…

8

Hmm, that makes sense. So then, how would we make it work at home? Set the computers’ subnet masks to 255.255.255.0 ? Do we need to turn off DHCP on the router so that it works all the time, unlike before?

9

I keep DHCP turned off unless there’s a reason I want additional PCs to automatically connect to the robot.

255.0.0.0 might be used if you plan on running more than one robot at a time, e.g., last year’s and this year’s robots together, or a neighboring teams robot at some joint demo.

255.255.255.0 is fine if you’ll only be using a single robot.