Answered: Bad bootup

Hello,
My teacher recently gave me a “broken” vex brain. The problem with it was that it wouldn’t save the program uploaded to it. With a bit of playing I found that that is not the case. It never seems to go into user code, transmitter or not. When the brain is turned on, the Program LED is solid green, not even flashing. After downloading a program, the LED turns off and the program is run. But when the brain is turned off and then back on, the same LED problem, and no code runs. Also, the “eye” never flashes. It is a very old brain, it’s seen many years.

I use mac and so I downloaded OpenVex and vexctl to program the brain after I found the problem. Looking through the vexctl code I noticed it sends a command it calls, return to user code. I sent that code directly and the program runs! I don’t have to re download the program to the brain every bootup now, but not I just have to carry my computer around with me.

The program I made for it was to simply turn on an LED in digital port 10. After the program is downloaded, the LED in port 10 is completely off, and then turns on. When the brain is turned off and then back on, the LED is very slightly on, sending return to user code, the LED turns off completely then on as the code says.

Now my question is, is there a way to force the brain into user code? I can wire up a small board for it, or add something to the vex brain board if needed. This brain will NEVER be used for competition again, so any modifications that would be needed is fine. I want to use it as a microcontroller for my own projects now. Is there a small circuit similar to the USB dongle I can use to send it into user code? Anything smaller then a computer will work for me.

Thank you,
Ian G.

To start, please refer to the post Get back to “Square One”. Does the Microcontroller work correctly with Default Code – it should power-up running the Default Code.

No, it did not last time I downloaded it, but I can try again tomorrow at school. It would work right after downloading, then it wouldn’t start after the robot was turned off and back on.

Be sure you download Master Code and then Default Code, not just the Default Code.