Slow blinking red light on Cortex

VEX V5 Technical Support OFFICIAL Tech Support
1

The team has recently been seeing a condition where the robot’s vexnet disconnects and sits with red LED slowly flashing. it seems to be arbitrary as to when this happens. As well, it will often recover and reconnect. Sometimes quickly and other times it requires a reboot of the cortex before a connection can be re-established.

We have:

  1. tried a number of different VexNet key combinations.
  2. made certain that we are running the latest firmware on both cortex and joystick (3.x)
  3. checked that the 7.2 batteries are fresh.

The VEX ROBOT Trouble shooting flowchart indicates that this is caused by a programming error. So that have restored to previous version yet the problem persists. If it is a programming error what type of error should we be looking for?

Any suggestions?

if this has been answered in a previous post I apologise, athough we have searched and didn’t find it nor a solution.

John
PiLons Team 5225A
2013 VRC World Championships Design Animation Challenge First Place
2013 VRC World Championships Division Excellence award
2013 VRC World Championships Amaze Award
2013 VRC World Championships Excellence Award
2013 VRC World Championships Programming Skills Winner
2012 VRC World Championships Programming Skills Winner
2012 VRC World Championships Judges award

2

Hello PiLonsCoach,

Do this issue happens while in tether mode as well?
Have you tried running the robot on the default code, to isolate a programming issue?

-Eli

3

Just last evening they attempted testing while tethered. Although they had to chase the robot about the field, it seemed to work.

So, our first instincts were, it must be the vexNet keys. Although we have 6 keys, and 2 controllers any combination fails whenever we include any pair of vexNet keys.

The only other possibility is batteries momentarily dislodging in the controllers because while tethered, the controller is powered from the cortex. That said we don’t feel that this is likely because we attempted to keep the controller as still as possible during all our tests.

We have ordered 2 more keys to assist us in our adventure but we were told that they are back-ordered, so at this point we’re out-of-luck. Unfortunately this will mean that probably will not be unable to attend our first tournament in a couple of weeks . C’est la vie.

If there is anything that we could attempt with our existing keys please tell us.

thank you,
John
PiLons Team 5225A
2013 VRC World Championships Design Animation Challenge First Place
2013 VRC World Championships Division Excellence award
2013 VRC World Championships Amaze Award
2013 VRC World Championships Excellence Award
2013 VRC World Championships Programming Skills Winner
2012 VRC World Championships Programming Skills Winner
2012 VRC World Championships Judges award

4

Oops, forgot to address this point. We couldn’t find anything labelled “default code” so instead we tried Single_Joystick Control.c from the RobotC sample directory and found that this also failed when using VexNet keys.

Same state, a slow flashing red LED.

At this point we assume that Trouble-shooting flowchart PDF is not accurately describing the situation, as the problem persists even with this extremely short and simple example.

John
PiLons Team 5225A
2013 VRC World Championships Design Animation Challenge First Place
2013 VRC World Championships Division Excellence award
2013 VRC World Championships Amaze Award
2013 VRC World Championships Excellence Award
2013 VRC World Championships Programming Skills Winner
2012 VRC World Championships Programming Skills Winner
2012 VRC World Championships Judges award

5

PiLonsCoach,

Whats the name of the LED blinking red?
Is it a single blink or a double blink?

Please clarify.

-Eli

6

On the Cortex it is the VexNet LED. And single blink.

Thanks,
John

7

PiLonsCoach,

The red VEXnet LED indicates there is a problem with the VEXnet link.
If interference is causing this issue, you should be able to operate the robot in the School parking lot or at your house without any issues.
If the problem is a faulty VEXnet Key, you should be able to try a “known good” set of keys and operate the system without any issues.

-Eli

8

What type of interference are you referring to?

Unfortunately, until we get the two new keys in we won’t be able to confirm a faulty VEXnet key ussue.

Thanks, John

9

PiLonsCoach,

It could be interference from the WiFi network at your School.
See if you can operate the robot at a different location.

-Eli

10

Again thank you for the information. Unfortunately, we’re in an industrial mall suite and although we could control our own (maybe switching wifi channels) we wouldn’t be able to control our neighbours.

Do you know what gHz/channels we should avoid to help reduce interference?

Thanks John

11

I found your response on an old post, so no need to answer. I will experiment by changing our wifi channels.

Do VEXnet keys wear out? I don’t mean by harsh use, but instead by continuous use. Since our teams only meet once a week, each meeting can last 6-10 hours. I have watched the group work through 12 pairs of charged batteries like a chain-smoker works through a pack. When a battery is showing ANY sign of voltage drop it is swapped out immediately so that they may relentless continue testing or practising.

I can’t complain as they have more than proved themselves in their short two years of existence, yet we have now gone through many keys with two new keys ordered for next week. 8 keys in 24 months. That seems like a lot.

Could this pattern of usage be the cause?

Thanks, John

12

PiLonsCoach,

Eight damaged VEXnet Keys in two years is a lot, and I’m not sure what would cause such failure rate.
In order to understand the cause behind this damaged units, we will need to get them back for further analysis.

Please contact support@VEXRobotics for return instructions.
Regards.

-Eli