Robot won’t connect via Ethernet

Hello CD, 5943 here.

We are currently at Tech Valley Robot Rumble and our robot wont connect through Ethernet. We are trying to prefill our compressor before a match, but the robot will not connect. We have checked all our connections and it has worked in the past. Nothing has changed on the robot.

Any ideas?

Thank you in advance

Are you getting any errors on the driver station? Also when you tether how long was it plugged in before the match?

We have been replugging in the tether and cycling power to both robot and the laptop and it’s still not connecting

Is the light on the driver station that says if the robot has code. Is that light green or red?

The robot will not connect at all. We do not get errors or anything. It just straight up won’t connect

We got it. The IP address was wrong for whatever reason. Either way. It works. Thanks for trying @Thequackmaster

For completion if someone runs into this thread looking for a similar solution, was the problem specifically the Subnet Mask being 255.0.0.0 (/8) and not 255.255.255.0 (/24)? /8 is what you use if you are static’d when attached to the field, unless you actually have a gateway set and then you can use the /24. /24 is what you use when tethering.

I’m thinking that they were directly connecting to the roboRIO instead of connecting through the radio so there was no DHCP server. If their laptop was using a static IP and the roboRIO was not, then the self-assigned IP on the roboRIO wouldn’t be on the same subnet. The easiest fix for this is to disable the static IP on the laptop. Forcing the roboRIO to use a static IP would also work.

Edit: The radio doesn’t have a DHCP server when it’s in bridge mode. So even if they connected through the radio, as long as they had a static ip on the laptop and the roboRIO didn’t then they wouldn’t be able to connect.

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Why would that prevent communication? If the DS and RIO are in the same /24 subnet (10.6.96.5 and 10.6.96.2, for example), then having a /8 mask shouldn’t make a difference.

Believe me, I really wish it wouldn’t. I’m constantly having to change submasks in the alliance station so that they can connect to FMS because they couldn’t directly connect to the robot in the pit. Most often static’d DS’s are set to /24 when they come up and forgot to switch it back to /8. This is with no gateways configured in either case.

If someone can explain to me why this is, I would love to get my fields connecting quicker.

I mean, on the field, the DS definitely needs a /8 mask; IIRC, the DS can talk to the FMS over a 10.0.100 subnet. What I don’t understand is why you’d need to restrict the subnet to a /24 to make it work in the pits.

Slightly off-topic, but where is the best place to learn all about the Rio/Radio/FMS/Drivers Station and how they interact? I know almost nothing about these topics, but want to learn more in order to help diagnose issues in the pit/on the field next season.

https://wpilib.screenstepslive.com/s/fms/m/whitepaper/l/608744-fms-whitepaper

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Nowadays the DHCP server is always enabled, so you will get DHCP leases in the pits at competition.

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