VEXnet 2.0 downloading problem

After upgrading to VEXnet 2.0 and all the new software and firmware, we have been experiencing a recurring problem with the robot connection (VEXnet keys) and possibly the cortex firmware. As of now, whenever we attempt to download a program (even an empty one), the program sometimes begins to download, but it always disconnects immediately and gives one of the following errors:

  • Failed to verify that the serial link is connected to a Robot Controller. Cannot communicate with VEX Cortex Slave CPU. Master CPU communication is working.

  • Failed to verify that the serial link is connected to a Robot Controller. Vex Cortex controller master firmware version (0.00) is out of date (4.22). Upgrade required

  • Failed to download user’s program file to robot controller. Error 'Failure setting program number into robot.

  • Robot controller failed to respond. Possibly not powered on or corrupted firmware. Or low battery condition. Or cable connections between controller and PC are wrong. Or incorrect port is selected on PC.

  • FAILURE. Flash write failure. File in robot is corrupted. Needs to be downloaded again.

This error occurs no matter which computer we download from or which cortex we download to. When one of these messages occurs, the lights on our remote and cortex both show the VEXnet LED as a slow blinking red light. Also, the cortex has a fast blinking green light on the robot LED and no light on the game LED, whereas the remote has no light on the robot LED and green light on the joystick LED. After blinking red a few times, the cortex LEDs resume to a state that looks similar to, if not the same as, when the robot is searching for a connection, but the remote LEDs stay in the same state.

We also discovered that some of the VEXnet 2.0 keys download successfully when paired together, but other pairings have the same recurring problem we explained above. We also discovered that when the cortex and remote are tethered directly with the USB cable, the program will download every time.

As additional information, we also do frequently use the VEX IQ features of RobotC on the same computer system. We are using RobotC 4.10, not easyC.

Your help is much appreciated!

Hello ElR123,

Thanks for the detailed email.
Can you please confirm which version of ROBOTC you are running?
You can find your ROBOTC version per the attached screenshot.

Doc1.pdf (114 KB)

We are using RobotC 4.10.


Thanks for the confirmation.
4.10 is an outdated version of ROBOTC, please upgrade to the latest version (4.26)

Also please make sure that the radio firmware on your VEXnet Keys 2.0 is at version 1.43 (see attachment).

This will greatly eliminate your communication issues.
Let me know your results.

PDF.pdf (105 KB)