[OCCRA]: Major VEX Controller Problem

Our main VEX programmer recently informed me of a microcontroller problem that we suspect began at the last tournament. During the tournament, the program arbitrarily disappeared from the microcontroller. Over the next few days, we were able to download programs, but they disappeared quickly. It is now at the point where we cannot download any programs. The com port opens up fine, but we get an error message along the lines of “Check your power supply or serial cable. Check Firmware”. We have tried downloading the master code and the default code, but neither will take.

Any thoughts?


  1. In general, since other teams read this as well, when my VEX robot begins acting flaky, I make sure the battery voltage is good and I download fresh firmware. The firmware name for EasyC V2 is called the Master code and the binary file name is VEX_MASTER_V7_4EASYC.bin. It is times like this when having a second unit and performing simple A/B testing makes live a lot easier.

  2. Make sure your battery is fully charged. You may also want to load fresh 1.5 alkaline batteries before downloading the latest firmware just to eliminate the possibility that your battery is causing your problem. OK, how does your battery cause the problem. Answer: You remove the battery and it measures 8.0 volts plus/minus 0.5 volts. That is open circuit or unloaded. Think walking on level ground – easy. Now: You plug the battery into the VEX controller - it now draws current and is loaded (but you are not measuring the voltage with your voltmeter). Think walking up a hill -harder. In this condition the battery voltage dips below 7.0 volts (working harder) and your VEX controller doesn’t operate the way you think it should (but you fooled yourself into thinking it was ok because you measured the voltage when it was unloaded – easy).

  3. Did you download the EasyC V2 Master Code (2008) [VEX_MASTER_V7_4EASYC.bin] or the older V1 master code (2007)? See the OCCRA Kickoff Powerpoint presentation for details. The older master code (firmware) will not work properly with EasyC V2 and OCCRA template.

  4. Bring your VEX robot to tomorrow’s competition. I can check your robot with my software and programming cable. We did have one bad VEX controller last year (I think it was you guys?) Does Roeper eat VEX controller’s instead of Wheaties for breakfast? - Hah!

  5. It is less likely but it could be a bad programming cable or even less likely bad laptop serial port or Easy_C installation. Let’s not go down this route until we have exhausted the previous options?

Hope this tides you over for today. See you tomorrow,