VexNet Will Not Reconnect

So I recently updated to RobotC version 3.08 but had the same problem with 3.05 a couple months ago. Out VexNet likes to disconnect periodically, but with version 3.04 the lights on both the Cortex and the joystick, the lights would always flash and reconnect.

However, with both 3.05 and 3.08 only the Robot light (or the VexNet light; I can’t remember at the moment) would be on, would stay on, and no other lights would ever turn on. The VexNet would not reconnect until I power cycled the Cortex, which is not permitted in the VEX competition unless the robot has never left the tile, if I understand the rules correctly.

What would be causing this problem? I’ve updated the firmware multiple times in each version, but only downgrading 3.04 completely erases this problem.

What would be causing the issue?

When did you recently upgrade, was it yesterday or before that? There are unfortunately two versions of 3.06 floating about, you need the one from March 7. Also, what hardware revision do you have (look on the bottom of the cortex), is it NC1, NC2, A3 or something else. If it is NC1 then read this thread, actually read it anyway and see if you have the same issue as described.

I upgraded today, the March 7 version, but I had the same issue with 3.05. I will investigate the Cortex tomorrow, but it does not the same issue mentioned in that post. The robot works fine with VexNet, connecting at first and then driving as it should, but when it disconnects as VexNet sometimes does, the lights on the Cortex just don’t flash to reconnect, whereas they do on the joystick.

Since 3.04 works fine for you, I suggest that you just play it safe and stick with it. I haven’t upgraded to 3.05 and 3.06 yet and am not planning to until after worlds. (well maybe I might try 3.05, but 3.06 seems to still have some bugs)

Oh and I think VEX determined that it was caused by old hardware, so if you have a cortex with the code that jpearman stated, you should get your cortex switched/upgraded with VEX. I think they said they were doing it for free.

The one from Mar7 is denoted 3.08 in the Help->About ROBOTC dialog.


Very well then, I guess I do have the 3.08 version. Good catch.

Good grief …

So version 3.06 is now 3.08, I just installed to check. I’m going outside to scream now.

So if you have the older cortex with the older code, you can ship it to vex and they’ll ship you a new one?

It may not be a problem with your code. My team had the same problem a couple of weeks ago and we called Intelitek and they said to check our 9V backup battery, so we did and it only had 5V. We replaced it with a new one and we don’t seem to have the problem anymore.

The thing is that once it disconnects it wont reconnect. Normally it reconnects.

We had the same issue, but we found out that the backup battery has a few purposes.
1) It will actually run whatever is wired directly into the brain.
2) It aids in reconnecting the VexNet when the signal is dropped. If the battery is dead, the signal will take longer to reconnect or will not reconnect at all.

All the backup battery does is power the VEXnet module and the processor that controls it if the main battery doesn’t have enough voltage. Even with the 9v the robot still wouldn’t connect.

Just test the battery with a multi-meter and if its under 8.5V replace it and see if you still have the same problem.

Serious? 8.5 V or do you mean 7.5? Our batteries generally charge up to between 8.5 and 11 V, but we only ever replace them when they get down to 7.5 V or below.

Edit: Just realised you were talking about the 9 V backup battery. :stuck_out_tongue:


We had connection problem too since we upgraded to newest version of EasyC 4 software. It happened several times during a qualify competition and practice also. I changed Keys, but not solve the problem.

I am talking about the backup 9V battery. just check it out with a multimeter or just replace it with a fresh one.

I just talked to Eli from VEX, and he told me that the issue with losing link and dropping to a Solid Green VEXnet light is a known problem with master code firmwares 3.20 and above (which ship with RobotC 3.05 and above). I gathered that there were a lot of changes in between the 3.17 and 3.20 firmwares. He said that it is intentional that the Cortex VEXnet light goes solid green, and it will stay that way, and not try to re-link with the joystick. He also said that they are working on a fix for this (for a future master code I suppose) , so that it will re-link if VEXnet drops connection. He said I could continue to use the older version of the master code and ROBOTC just fine, I only wouldn’t be able to use the new integrated motor encoders.

Take all of this with a grain of salt; I just finished doing a brain dump of all the info I could remember from that call (of which this info is a paraphrased subset), so I could be wrong on some of this.

Thank you for that, it explains it perfectly. Do you have any idea when the new master firmware will be released?

Just talked to a guy from VEX, and he said (I believe) they might develop the new master code and
A. Send it out to everyone (soon)
B. Have EasyC and ROBOTC make updates with it
or C. Just release it right before worlds.

i really hope they release new mastercode reallly really REALLY soon!!!