[OCCRA]: OCCRA Vex Net Please read 11_06_09

[Mike Martus]

In an effort to get all teams up to speed with VEX Net please read below. We want ALL teams to be successful with our new VEX Net system. Many have it working great.... a few are lagging in effort and need a little push.

WE NEED YOU TO COME PREPARED TO RUN THE VEXNET SYSTEM AND WE WILL ONLY ALLOW TEAMS TO RESORT TO THE USE OF CRYSTALS FOR SITUATIONS WHERE WE ARE UNABLE TO GET THE VEXNET WORKING.

[marccenter]

Mike,
Good news. The 3 original VEXnet units that were sent to VEX robotics are in the mail returning to us. If they arrive by tomorrow evening, I will bring them to the Waterford Tournament on Thursday. After testing, I would like to return them to their rightful team owners. See you Thursday!

[Rick TYler]

For what it's worth, we ran a 27-team VRC tournament last weekend with two or three VEXnet robots, and they worked flawlessly. After this, we are ordering VEXnet for all of our team's robots this week. Crystals are too much hassle by comparison.

I hope your experience ends up just as positive.

[apalrd]

You must not have heard about the problems OCCRA has had with VEXnet. Around half of us have killed our RC upgrade units or they were faulty. That is why OCCRA still allows us to use Crystals if we can't get our VEXnet working. I would agree though, that VEXnet helps with competitions, and I was in favor of the VEXnet upgrade until I fried my VEXnet upgrade. I no longer like VEXnet, as it has been show to be unreliable. Hopefully Innovation First will fix this in the future.

[brickmaster2]

What did you do that fried your Rx Upgrade? I want to make sure I don't screw up the new one Mr. Center gave us.

[apalrd]

No idea.
Marc Center seems to think that an error in the firmware caused something to get corrupted when we loaded code. Other than that, it just died when we were working on it before a competition.

[marccenter]

Andrew,
When a VEX microcontroller goes down I have generally found that
1) Student programming error is major cause (> 80%)
2) Student programming with low battery may be potential cause. A firmware
reload appears to fix this "anedotal" problem. ( < 10%)
3) VEX microcontroller hardware error is very small percentage of the cause
(1 unit from all of our OCCRA units so far < 30 units).

This year OCCRA is using VEXnet. We are using the older style VEX transmitters upgraded with VEXnet hardware. Some competitions are using newer style VEX transmitters that are different from our units.
Our VEXnet transmitters and receivers have received a firmware update from IFI. We need to experiment with them a little more before we jump to any conclusions about their behavior.

[apalrd]

1.
How could code cause problems for the VEXnet? If the code encounters an error, and does not update the master by the time the master receives the next data packet (18.5ms), then the PGM STATUS light will turn red and the master will kill the user. As far as I can see, this does not cause any problems (I actually use this as a stop switch). It the VEXnet system can be killed by student programming error, then the system is not designed correctly.

2.
If the battery is low, the only reason for a problem is if the battery is low enough to cause the processor to reset. This *shouldnt* cause a problem for the VEXnet since you would only need a new battery and to reload the code. As far as I know, the VEXnet dosen't actually store any data except possibly to buffer it in RAM while transfering. Once again, if it can't handle a normal situation, then it is not designed well.

3. Hardware problems are reasonable. I understand that these are early models and may have a few bugs.

New VEX transmitter? I can't seem to find that on the VEX site... Seems like they still sell the 75mhz system and VEXnet upgrades, no new transmitters yet (although they have hinted on one to be released next year). Unless you mean they released a firmware upgrade on the VEXnet upgrades for the transmitter, I can see no difference... Although they did hint to the release of a new VEXnet transmitter that is more like a ps2 joystick, which will have VEXnet only operation. That will come after the Cortex microcontroller, which has not yet been released.



Could you possibly be thinking of the RC and not the RC Upgrade? I am talking about the RC Upgrade, not the RC itself. The RC works fine.