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VEX-to-VEX wireless communication using ROBOTC? 
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Joined: Mon Jun 11, 2012 9:28 pm
Posts: 37
Post VEX-to-VEX wireless communication using ROBOTC?
Hey all,

I'm working on a project at school with ROBOTC and the VEX system. Basically, getting it to work will involve 2 cortex units to communicate wirelessly. I'm willing to do hacking/soldering if needs be. I need to send 10 or so bytes of data as many times per second as possible. Low latency is very important.

Is there anything I can purchase/use?

Thanks!
Daniel


Mon Apr 15, 2013 7:35 am
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Joined: Wed Feb 09, 2011 1:08 am
Posts: 27
Post Re: VEX-to-VEX wireless communication using ROBOTC?
have you seen this:
http://www.robotc.net/firewiki/index.ph ... =Main_Page

Also I posted 2 related topics Here:
http://www.vexforum.com/showthread.php?t=74951

http://www.vexforum.com/showthread.php?t=75543

It's not that hard to configure 2 xBee radios in Point to point mode and pass data back and forth.

Cheers Kb


Mon Apr 15, 2013 9:31 am
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Joined: Mon Jun 11, 2012 9:28 pm
Posts: 37
Post Re: VEX-to-VEX wireless communication using ROBOTC?
Perfect, that's just what I was looking for. Do you know anything about the latency with xbee?


Mon Apr 15, 2013 2:45 pm
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Joined: Wed Feb 09, 2011 1:08 am
Posts: 27
Post Re: VEX-to-VEX wireless communication using ROBOTC?
I have not measured it specifically, however when using the XBee based remote control project using binary based packets I was able to get responsiveness similar in feel to the VexNet link. (start / stop / turn ) If you keep the payload size on the small size, and use a binary (vs ascii) based representation you should be able to see low latency.

I did a series of experiments thinking to post the results (but never did) comparing XBee to Direct Wired (Uart to Uart) for an Arduino based Logging function. The Sole function of the Arduino was to log data from the Cortex to a SD card. I found when using XBee the amount of data and Frequency of write cycles needed to be scaled back slightly, but more noticeable was once you pushed too much data (based upon Cortex Performance) through the link, the Xbee based link would drop data, while the direct link would get the entire package of data but the time between updates would increase (blocking write calls)

Cheers - Kb


Wed Apr 24, 2013 6:32 am
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