Problems with Cortex

One of the robots we have been using will work as it should when connected to the computer via the USB cable. We unhook it from the cable and sit it on the floor to test the program. When the Cortex is powered up, the Robot light is green, the game light is flashing an amber color very fast and the VEXNet light will slowly flash an amber light. Within five seconds all of the lights will flash red one time, and the cycle repeats itself.

We have switched out the batteries, twice during one class period and this doesn’t solve the problem. We have re-downloaded the firmware, twice and we still have this issue. I have tried to follow the flowchart that I have for troubleshooting, but the codes we are getting with these flashing lights are not addressed on the chart.

Any help would be appreciated!

Was the cortex new? Old cortexes often run into very odd problems.

Sounds like it is looking for a VEXnet key, are you planning on using the joystick or are you trying to run stand alone without one ?

No, we are not planning on using it for the current task. But it does make me wonder if the setting on the computer is correct or not. I will check this out.

Assuming you are using RobotC, you need to download for “USB Only” under “Vex cortex communications mode” in the Robot menu. That allows the cortex to run code without a VEXnet connection.

Yes, we are using RobotC. I checked the computer being used and it was set to either USB or VexNet. I am home now, but I will give this a try tomorrow. Why would it not work if it is set to either mode of communication? Thanks!

The “comms mode” is a badly named feature, it relates more to how the cortex starts up, should it look for a VEXnet key, is it in competition mode etc.
“USB Only” really means run the program standalone with no joystick (ie. no VEXnet key) When using a VEXnet key and joystick, I usually select “competition”.

I made this switch upon arriving today and everything now works as it should. Thank you.