Re: Intermittant control with radio
 

IFI will allow you to test in the pit. However, if they see you doing it for long periods (2 minutes or more) they will come talk to you. If you're using a competition channel and not the default channel, you should expect IFI to stop the competiton and come talk to you immediately.

Re: Intermittant control with radio
 

Page 5 of the "At the Event" rules clearly state otherwise:
Just because teams have done it successfully without getting yelled at doesn't mean it's a good idea. All these complaints of suspected interference are even more reason to only use the tether in the pit area. How would you feel if you lost a match due to radio interference, only to find out that someone was operating in the pits and may have caused the interference?

Re: Intermittant control with radio
 

I would agree it's against the rules- however, it does go on and if a team feels their radio is not working how else are the supposed to test it? You often can not remove your robot from the building.

Also, it wouldn't bother me in the least if we were told we caused a robot to lose a match, if I'm using the default channel with my team number set correctly. At that point it was a failure with IFI, not my team.

EDIT: Ohh, if my team lost because of radio interference? It depends on the situation. If they were using a competiton channel, I would be furious with the team. If they weren't- I would think IFI was trying to hide something.

Re: Intermittant control with radio
 

IFI keeps records of all occurances that teams function. More or less from the time your bot is powered on, IFI knows what channel you may be on, thethered or not and even as much as they can check your battery levels. Now i knoiw that when i was helping out IFI in NYC, there was one occurance when a team had to test radios and they were brought outside supervised and assisted by the IFI representative on site. If you ever need to test radios please get an IFI rep to help you as they normally can figure out the problem in under the length of a match. Also they will then know if you need a donor or a replacment unit while at the competition.

Re: Intermittant control with radio
 

I've had a chance to talk to Tom Watson of IFI at length during both the Peachtree and Palmetto Regionals. During the match, IFI has a scanner on all four channels. They watch very closely to montior the data rate and packet losses. All too often, teams blame the radio communicatoins first, even thoguh it is rarely the culprit. It is mainly for this very reason that IFI has a representative at each event - to cull misguided perceptions.

Re: Intermittant control with radio
 

You need to talk to the IFI representative at your competition. Their scanners will give a lot of information about any interference that goes on during the matches. They can also give you tips on what else might be causing problems.

Re: Intermittant control with radio
 

At SBPLI we had a damaged RC tether connector that caused us to have intermittent radio broadcasts of garbled data only while on tether.

IFI had a special dongle they loaned us temporarily for the competition port that put us on a frequency no one else was using so we could close our arms without using the tether.

We were fine on the field, but couldn't use tether in the pits. We repaired the connector after the competition.

Re: Intermittant control with radio
 

With IFI being such a small group, and spread so thin, I find it suprising they have the time for that kind of personal attention. Kudos to IFI.

EDIT:
I feel a little harsh to Dave Flowerday on post #33 of the thread, so let me first aplogize.
For me, IFI presents us with a control system that I believe has almost no faults. When they have different channels, I assume that teams can use different non-competiton channels and have no worries. I also assume, that IFI produced a radio system that can shift through the garbage and grab your own packets by team number, even if others are on the same channel. This belief is even further enhanced when at Annaplois, a full practice field setup, including radio control was setup about 100 ft from the competition. They have done such a great job with the control system, I feel that any interference anyone is receiving is the result of an issue with your robot, or malicous by another team.

Re: Intermittant control with radio
 

Not sure if this was posted before, if it was, I am sorry.

We had this same problem at our regionals where we had some packet loss. After some talks with the innovation first guy, he told us that our problem could be caused by having our radio right next to the main circuit breaker. We moved our radio farther away from it, and havn't had this kind of problem since. Try moving your radio away from all other electronics, and have the ifi guys run a check for you every time you go up (if you are going to atlanta). They can detect packet loss, and see just how much data your robot isn't getting.

Re: Intermittant control with radio
 

So here's the deal: first of all, IFI does not manufacture the radio modems. They simply resell them (they're made by Ewave (unless Ewave is a division of IFI, but I doubt it...)). Second, when there are multiple fields in operation, IFI carefully selects the channels used by each one to minimize any chance of interference. Notice I say minimize: I work for a company that happens to dabble a little bit in RF, and one thing I can tell you for certain is that RF interference is very hard to predict and understand. IFI can reduce the risk, but they cannot eliminate it. These radio modems work on the same frequencies as 900MHz cordless phones and a million other things. Additionally, as you have mentioned, IFI protects their data stream with both a team number and checksum to prevent a robot from reacting to invalid or corrupted signals (those who were around in the Rnet days really appreciate this!). However, all that does is cause the RC to ignore corrupted packets. Meaning, if you're transmitting something on the same channel as an OI, the robot won't go haywire, but it will lose radio contact and just sit there, disabled. If two teams are on the same channel, the RCs cannot simply pull each team's stream out based on the team number. More likely, neither RC will get a valid signal, and both will be dead. This is affected by how far each OI is from it's RC and from the other RC, etc.

The bottom line is that I personally would feel really bad if we were using our robot wirelessly in the pits and later found out that while doing that, someone was sitting dead on the field. Sure, the likelihood of us being the cause of the interference is low, but no one can be certain. My advice, and the way our team operates: only operate on tether in the pits, unless specifically instructed or otherwise granted permission to work wirelessly. Don't just fire it up thinking it will be OK. FIRST made the rule I referenced earlier for a reason.

Re: Intermittant control with radio
 

the radios used are FM - which have the characteristic of 'capturing' the strongest signal, and ignoring all weaker signals on the same frequency

so if you are on the field and your bot is right next to your OI the link will work, even if someone in the pit is on the same channel

but once you get some distance between your OI and your bot, which transmitter will be hitting your bot with the strongest signal, and which bot will be pinging back to your OI depends on a lot of factors (where you receiver is located in your bot for one thing, which way the antenna is pointing...)

it would be very easy for an OI in the pit to capture your Bots link, then since the team numbers dont match up, the link will go dead and your bot will do nothing.

Re: Intermittant control with radio
 

I took a look at the Ewave site. We definately use there radios. The Screamer422 , is my best guess.

The base and remote use 2 different frequencies to achieve full duplex. Which means each "channel" is actually 2 frequencies being used. The base broadcast range is 926Mhz - 928Mhz. The remote broafcasts at 902MHz - 904 MHz. Frequency spacing is 50 KHz. THe range on the modems is approximately 300ft.

EDIT: I'm so concerned with looking at the spec sheets I failed to notice the following paragraph:
Ewave's SCREAMER422™ RF Modem is designed specifically for use with the Innovation First Robot Controller used in the US First Robotics Competition and, unlike all other Ewave RF Modems, the SCREAMER422 features a RS422 interface.

Re: Intermittant control with radio
 

Lots of interesting discussion but my question still remains, where does one legally test radio communication at a regional? I knew that the rules are require tethered control in the pits but .... At the Lonestar regional it would be simple enough to roll outside the front door except I don't know where one would get power for the OI... We were at a loss of where to test and just made a change and had to use the next round as a test which is not ideal.


Thanks to all you experienced posters who can quote the rule book


APS :rolleyes:

Re: Intermittant control with radio
 

There is no "Legal" place to test your radio modems, except during a match. But if you do need to test them, find an IFI Representative on the field, explain your situation and they normally will help you out.

Re: Intermittant control with radio
 

Okay if anybody is still lurking and watching this thread. Our team apeared to have some control issue at the Lone Star Regional. Drivers reported dead stick type of complaints. Lots of good ideas for troubleshooting have been posted as well as an interesting discussion of the Ewave radios ....
An update,
I have tested the robot in a gym on radio and students conducted a similar test in the courtyard in the weeks following the competition. We have made no changes since are last few rounds at the competition.


Does this rule out any of the suggestions and seem to implicate others? I have never experienced this in the previous three years at the regional.

I trust my drivers when they tell me it wasn't working but now I wonder if maybe it was a mechanical issue with our wheels and the carpet. The gym and courtyard test obviously where not on carpet.... :confused: