Re: Intermittant control with radio
 

I am the lead sponsor for the team which started this thread.

The discussion about the reset button on the RC brings up possibly a related issue we had at the competition in addition to the erratic performance on the field. When the round ended or even in the pits on tether, after shutting down power to the robot the team color LEDs would continue to blink. They would shut off after one hit the reset on the RC. Are these problems related??? The back-up battery and LEDs being new this year leave me with little experience in their operation.

Thanks,

APS :confused:

Re: Intermittant control with radio
 

when you turn off the main battery the backup battery continues to power the RC (and team color LEDS)

think about it - thats what the backup battery is for, to keep the RC running when the main power dips

so how does the RC know you actully wanted to turn the main battery off?

ans: you hit the reset button.

Re: Intermittant control with radio
 

We found our that reset turns off the RC by accident. Before, we would pull out the back-up battery to cut off power, which led to a loose connection in the back-up battery.

Re: Intermittant control with radio
 

As someone said before, the problem might be in someone else on your frequency. That sounded exactly like what happen once when we were running two robots in one room without realizing it.

Re: Intermittant control with radio
 

The frequency problem affected us last year. About 10 seconds into the match the robot stopped suddenly. No matter what we did, it would not move. An IFI representative said that the OI was sending data, but the RC was not getting it. Turns out that either someone was running a robot on the practice field or in the pits with a radio, or some other radio signal (RC cars were running around everywhere)

Re: Intermittant control with radio
 

If the IFI guy did not explicity tell you that there was interference, then there most likely wasn't. FIRST runs frequency scanners which will detect anyone using the radio modem when they shouldn't be (i.e. they aren't playing currently).

Matt

Re: Intermittant control with radio
 

This may be related to your problem.

We noticed our robot was chattering quite a bit after uncrating it at the Plametto Regional. What I mean by "chattering" is that the motors seems to be pulsing instead of having a smooth operation. The symptoms disppeared when we connected our laptop to the PROGRAM port.

The problem was discovered to be caused by printf statements left in the code. Removing these calls solved our problem.

Many thanks to Tom Watson (Innovation First) and Ed Sparks for your help in solving this!!

Re: Intermittant control with radio
 

ya my team had the same problem, but it turns out that first of all our receiver was too close to all of our electronics creating interference. and that there were so many radio waves bouncing around in the stadiums that i'd say would be impossible to find a place in there where there wasn't any interference. but we ended up solving this problem by just moving the receiver higher up the bot away from the electronics and we just used a tether while practicing because it also seemed that the competition transmitters are much more powerful than the ones given in the kit.

Re: Intermittant control with radio
 

after cutting the main (12 volt) power to your rc, with the back up battery at a high charge connected will continue to run for 255 seconds. In that time, the leds do flash, the rc leds should stay lit and the radio modems will try to continue to "talk" with each other.

Re: Intermittant control with radio
 

Did they say why this could be a problem only with the radio and not when connected with the tether or to the program port?

Andrew: We do have a couple debugging printf statements in the code as it stands. I know it's too late to really be much help; but it would be very valuable info for next season's robot.

The programmers at the school know what files the statements are in and how to get rid of them. Might be worth testing.

Sean

Re: Intermittant control with radio
 

In the past we've had problems with the radios cutting out on us. The problems have ranged from low voltage(when we loaded all the motors at once), bad/loose radio wire, and errors in our code (infinate looping and that sort of things).

Re: Intermittant control with radio
 

Furthermore, when plugged into the competition port, the OI is opened up to a number of competition-only frequencies, which are very unlikely to be duplicated out in the pits or practice field (unless someone has a dongle on their OI to enable them).

Another thought that crossed my mind reading this thread: programming. I've heard from a number of people that floating point math slows the PIC procesor to a crawl. It's possible that the RC is processing too much code, or too many operations, where it can't meet the time requirement to loop properly. I see a number of warnings in the code saying "warning: bad things may happen if _____." Could this symptom be one of the bad things referenced?

Re: Intermittant control with radio
 

Indeed that problem could occur. While we never use floating point math, it is very very slow, but a worse problem existed for us. Our encoders were digital, counting gear teeth passed, and were linked into interrupts on the OI. We found out that they were firing at about 2000 times per second at full speed, which was interfering with the datastream between the master and the user (the IFI guys told us to protect our variables, but I still don't see the chance for desynchronization in the code we had--we just overtaxed the system, I think). It caused the robot to be jerking and nigh on uncontrollable, as well as to fall in and out of autonomous. Oddly enough, the problem only occured on radio, not on tether, but we were 99.99% sure it was not a radio interference problem.

Watch how many interrupts you fire, if I may throw another warning into the mix!

Re: Intermittant control with radio
 

Next question is where does one legally test radio communication problems at a competition? We wanted to test if our radios where bad by switcing out with spares and also if moving the radio from inside a angle brace to outside. Can one leave the building and test on the sidewalk...
I appretiate hearing some of the more specific ideas regarding code issues that may be causing issues.

thanks,


APS :confused:

Re: Intermittant control with radio
 

I hear a lot of teams talking about interference- someone being on your frequency, causing your robot to go out of control.

It is simply imossible for this to happen- unless there was malicious intent. You set the team number on the OI and RC for a reason. The RC won't accept a packet (radio information) unless it originated from an OI with the same team number as itself. So unless someone set their OI to your team number, you're getting your own data.

It's possible that if someone is on your frequency, that too much "information" is in the air. However, during competiton, the controllers use channels that are not the default for the control system. They are avaliable, but a team would have to directly set their control system to use it. Malicious, if done at a competition if you ask me.