Cannot tether vexnet and joystick

I have been working since 6 this morning trying to establish communication between my joystick and the cortex. I paired one set with no issue but the second one will not communicate.

I updated both units but when I tether them together they will not communicate.
Plug in the battery
Connected via usb
Joystick off
Cortex switched on
Cortex game light fast flash green
Cortex robot solid
Cortex vexnet nothing
Joystick vexnet light solid green
I have tried holding in the config button
Nothing seems to work, any ideas

Did you try updating the mastercode on both of them from the computer?
Also, remember that VEXnet keys don’t get paired together, cortexs and joysticks do. (The VEXnet keys have no memory)

Rodney Burley,

Follow steps one and two in the attached Guide.
If you still have the same issue, check the flowchart on page# 3 (attached).

Cortex User Guide 0811_NEW.pdf (986 KB)
VEX_Robot_Troubleshooting_Flowchart_0811.pdf (518 KB)

@Rodney: These resources are invaluable and are my first “go to” when experiencing Vexnet difficulties.

@Eli: One suggestion for the flowchart: There are several places where it says “Update the Vexnet firmware”, with a link for finding the utility. However, once I had downloaded and installed the utility, I didn’t know what to do next. I could only find the utility available from my list of programs (as a separate program) – I was expecting it to be available in from a menu tab within EasyC. In addition, there needs to be more explicit instruction on which plugs/ports to connect to.

I would suggest more explicit instructions on how to “Update the Vexnet firmware”, such as:

How to Update the Vexnet Firmware
Although the Vexnet Firmware Upgrade Utility is included with the purchase of programming software (e.g., EasyC or ROBOTC), it is accessed separately from your START menu or list of programs. Firmware must be downloaded twice: once to the joystick and once to the microcontroller.

  1. From your Start menu or “All Programs” list, open “IFI Vexnet Firmware Upgrade.” If you do not have this utility, it is available on the “Downloads” page at
  2. To download firmware to the joystick:
    *]Install batteries.
    *]Using an A-A USB cable, connect one end to the USB port on your computer and the other end to the USB port on your joystick (Vexnet key must be removed).
    *]Follow the instructions on your screen in the Vexnet Upgrade Utility Window. When download is complete, the message “Vexnet is up to date. No action required” should appear.
    [/LIST] [/INDENT]
  3. To download firmware to the microcontroller, repeat the steps from #2a - 2c above for the microcontroller. Again, remember to remove the Vexnet key to allow connection of the microcontroller’s USB port to the computer.

Once firmware download is complete, the joystick and microcontroller must be paired. Refer to section 1 of the Cortex User guide.


One thing I find is that the “Curse of Knowledge” often results in technical documentation that skips too many steps and thus, is not as useful as it could be for “dummies” like myself. My team members and I do a lot of “head banging” (sometimes wasting 2 - 3 hours to figure out a simple procedure that could have taken 5 - 10 minutes) because we’re not able to “read between the lines.” Including more “obvious” steps like the above would save time for novice users.

Thanks for the feedback.
Also more detailed instructions on how to update the Firmware on your Cortex are found under the help tab, within your programming software.

Upgrade Utility.jpg
Show Getting Started.jpg