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Unread 01-03-2009, 15:07
rrossbach rrossbach is offline
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AKA: Ron R
FRC #2607 (RoboVikings)
Team Role: Mentor
 
Join Date: Nov 2008
Rookie Year: 2008
Location: Warrington PA
Posts: 90
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Re: "No Comms"

Quote:
Originally Posted by David Brinza View Post
"No Comms" is not a DS problem - it's a failure of the link between the robot and the field wireless access point.
I'm not sure that's 100% accurate as written. "No Comm" does indicate a failure of communication between the DS and the cRIO, and that could certainly be due link failure between the robot and field wireless access point. But as I understand the network architecture, it could also be due to a number of other causes:
- dropped UDP packets on the field network, for example due to traffic congestion, radio interference, etc
- a software error in the cRIO firmware causing comms to be momentarily interrupted
- a software error in the DS firmware
- etc, etc

Quote:
Originally Posted by David Brinza View Post
Unless ALL of the robots lose their links in a match, the problem lies within the robot.
Based on my observations, I feel 99.9% certain that that is NOT correct. It looks like all of the DS positions have at least some components of their comm links which are independent - for example:
- each DS position has it's own ethernet tether back to a patch panel
- it also sounds like there are six different individual wireless AP's on the field, each with it's own SSID and WPA config which is setup through FMS at the start of the match
- etc, etc

Saying that a comms failure automatically indicates a problem with the robot is not only incorrect, it also implies that the problem lies entirely within the teams' control to diagnose and resolve. Based on what I observed at the NJ regional this weekend, with multiple unpredictable comm failures on the field, I don't think the problems are solely within the teams' control.

I would STRONGLY encourage the folks handling the FMS to apply sound engineering and diagnostic principles to this problem. There are definitely issues with the DS<->FMS<->cRIO comms during matches, and there are a number of different parameters which should be checked, double-checked, re-checked, and stress-tested

If there's anything I can do to help out with this, please feel free to let me know via PM. It was personally disappointing to see how these issues adversely impacted so many teams' experiences during the NJ regional - due to alliance pairings, it impacts not just the team(s) having a problem but also many teams (such as #2607) which did not have any comms problems.

On a brighter note, BRAVO to the folks running the field this weekend - they did an outstanding job trying to find work-arounds and get the matches running as smoothly as possible.

Thanks,
Ron
Team 2607 - software mentor
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