VexNet 2.0 won't pair

I just got a pair of VexNet 2.0 keys. I can’t
get them to pair up. Cabled pairing is normal and the VexNet 1.0 keys pair OK.

Here are the indications I’m getting.
Robot - slow brief green flash
VexNet - fast yellow flash
Game - fast yellow flash.
VexNet Key - solid blue
Battery is fully charged

Joystick - solid green
Robot - off
VexNet - fast green
Game - solid green
VexNet Key - slow brief blue flash
New Duracell AA batteries

Both are up to date from EasyC v4.2.1.7 (latest). The VexNet 2.0 Radio
Firmware Update v1.43 reports both keys are current.

Am I doing something wrong or is there a latent issue?

Mike Blazer

Hi Mike,

Thanks for your detailed post.
Have you used the IFI VEXnet Firmware Upgrade to update the master code in the VEX microcontrollers & Joysticks?
If so, can you please confirm the version of master code you are currently running on your units?

I await your confirmation.

mastercode.pdf (90.9 KB)

Yes. Both are at 4.22. I just finish updating all our hubs Cortex/Joysticks (42 systems).


I appreciate the confirmation.
Is this the only system (out of the 42) that is not able to pair?
If so, please contact for a return instructions, as we will need to analyse the system in our lab.



My problem children started working after I paired them separately with another Cortex/Joystick set. I’m not sure what went wrong, but they are working now. At this point, the Second Law of Maintenance comes in to effect:

  1. If it works, don’t fix it.
  2. If it starts working, stop fixing it.
  3. If all else fails, read the instructions.


Glad to hear everything is working.
All the best.


Some of our teams (3 out of 34, so far) appear to be having the same problem. The LEDs are responding as previously listed. The problem clears when the either the problem Joystick or Cortex is paired with another unit then re-paired with the original unit.
Without knowing the internals, it seems that the Joystick or Cortex has a setting for the VexNet 1.0 keys that is incompatible with the VexNet 2.0 keys that gets reset when paired with a new device. This ‘setting’ is not cleared when the units are re-flashed with the current firmware.
Our teams normally get the same Joysticks and Cortexes each year. The off-season maintenance involves flashing the units to the latest firmware and loading the BEST default code in the Cortex. We leave the pairing and calibration to the teams. This would indicate that the problem is sporadic.
So far, I’ve been unable to duplicate the problem once the units have been successfully paired. I so love intermittent problems.


At Demo Day we had 7 more units that wouldn’t pair. This appears to be a bug in the Joystick. In each case, I paired the problem Joystick with another Cortex (wired, then wireless) and then re-paired with the original Cortex.