Quote:
Originally Posted by squirrel
How about using a remote control to select one of 4 (or 16) autonomous modes after the field initialization?
I'd be playing with the hint board and last year's robot to see if I could make it do different things just by "changing channels" on an old TV remote (available at any thrift store)
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My initial suspicion is that you are right about using the IR to switch to one of four possible auto modes after the field is set up, but I have a few other thoughts to add based on our experience of using IR remote controls and PICs to run mini-sumo robots for the past several years.
First of all is the issue of channels. With RF transmitters you can change the crystal or frequency synthesizer to transmit your signal on a specific wavelength, and tune your receiver to only receive signals transmitted on that wavelength. Pretty much all IR remote controls, as far as I know, operate on the same (or overlapping) wavelengths of light. Therefore everyone is "talking" on the same "channel".
To make the signal stand out from the background "noise" IR remotes flicker the LED on and off. 38kHz is the standard for the Sony IR protocol, but other brands use other frequencies. The receivers are tuned to only receive a signal that flickers at the correct frequency. Since these flickers all occur in the same wavelength, however, they can jam each other when more than one signal is emitted at a time.
This means that having robots controlled by IR signals coming from more than one source, when each source is transmitting at the same time, could present problems. (I believe someone mentioned the challenges in programming more than one Lego League RCX unit in a room at the same time and the need to control IR reflections.)
It is also much easier to buy a $4.00 multi-brand remote and program it to use a given IR protocol (IE the Sony Protocol) than it is to build a Learning receiver. (You can receive a Sony IR signal with a PIC, a PNA4602M, and 12 lines of BASIC code. Reprogramming the remote requires four button presses.)
So why a "learning" receiver... perhaps because (as suggested earlier) the receivers will learn a signal from the field crew at the regionals. This way FIRST could ensure that the signal and modulation they are using are not used by any commerical IR remote control units, making it less of an issue if people in the stands happen to have "IR keychain remotes" and such.
However it is also possible for the RC... when hooked up to an IR LED... to be programmed to emit an IR signal. All you do is pulse a digital output, really. Each team could be assigned a particular code (team number, perhaps), and would train the receiver to pick up on this signal so that they could test whether or not they were transmitting properly. Perhaps you score by transmitting your signal to a goal. But that kind of clashes with the whole "jamming" problem.
In any case, I promised myself I wouldn't get tied up over the game clue this year... congrats to the GDC for making me break that promise.
Jason