PO Channels

[Kyle Fenton]

Hey I presented in the NASA conference today in Providence RI. I had a major problem, that I couldn't run the robot, because the user brain, or the user controller, was keep restarting the PO channels. And it would never link up. I think that it is being jammed on something at the same frequency in the convention center. Bob was there from Buz robotics, and he contacted Mike from Buz to try to help me. He said to to change the team number on the user brain, and to make sure that it was set to the same on the robot brain. I did that but I was still getting the same results. Any suggestions?

[David Kelly]

Originally posted by Kyle Fenton
Hey I presented in the NASA conference today in Providence RI. I had a major problem, that I couldn't run the robot, because the user brain, or the user controller, was keep restarting the PO channels. And it would never link up. I think that it is being jammed on something at the same frequency in the convention center. Bob was there from Buz robotics, and he contacted Mike from Buz to try to help me. He said to to change the team number on the user brain, and to make sure that it was set to the same on the robot brain. I did that but I was still getting the same results. Any suggestions?

we had the exact same problem on our robot for 2000 after the season was over. we thought it was a cell phone or a pager or something like that. we could never figure it out. it was fine after we just wiped the program and started over. i have no idea of what it could be.

[Joe Ross]

The robots radios run at 900 mhz. Any cordless phone or other device that uses that range (which is very common) will cause interference.

The IFI system uses the team number to keep the robot from going crazy if there is interference. If the team numbers on the operator interface and the robot controller do not match, the robot won't move.

If there is intermittent interference, the robot will work most of the time and then appear to shutdown for a little while.

If you plan on doing more of these demos, you should make a "Yellow Dongle". This allows you to access more radio channels and increases the chance that the robot will work. There are instructions in the Control System manual. Dr. Joe also wrote a white paper about it: http://www.chiefdelphi.com/papers/Ye...ngle011301.doc

[Joe Johnson]

Your robot and controller use Channel 40 if there is nothing plugged into the competition port.

If you plug in the official competition controller or if you have made a "yellow dongle" or the equivalent, you can get access to other channels.

Channel 40 is the dirtiest of all channels. I never recommend using this one if you have a choice.

The remaining channels you can use with the dongle and the switches on the front of the Operator Interface (OI) are:
Channel 4
Channel 13
Channel 22
Channel 31

Note that setting the channels is not something that is done at any time but only at set times.

The OI only sets its channels at wake up. Also, the Robot Controller (RC) only scans for new channels at reset time.

So... you have to set the OI switches, then reset the OI, then reset the RC, in that order.

Be sure that you reset the RC by turning off the robot or by hitting the reset button on the RC.

Obviously the "Robot Reset" button on the OI needs a valid radio link in order to function -- this is obvious but I have tried to reset the robot this way more times that I care to admit ;-)

Finally, as the RC scans for channels, it looks not only for a valid signal from an OI broadcasting on a particular channel, but it also looks for a valid signal with the same channel number as the one that the RC is set to.

This keeps someone from accidentally taking control of another team's robot.

Finally, I have spoken to Tony about the issue of other 900Mhz devices causing problems and he says that it is quite difficult to happen in practice. Basically, the IFI stuff is just under the legal maximums for signal strength. If the other device is also at this limit (not always the case but possible) it has to be CLOSER to your robot and ON THE SAME frequency band before it will cause any trouble at all. As a practical matter, they have not been able to cause any problems with cell phones.

Good luck.

Joe J.