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Is there a way to wirelessly transmit data (preferably a string but numbers will do) in between 2 Raspberry Pis? The data must be transmitted without use of bluetooth or internet and have a range of about 40 feet. It can use GPIO or USB or anything else. Also the smaller the better! The data would be GPS coordinates, time and some other numbers and strings. In my research I found this Raspberry Pi Forums post but I am not sure if it would work.

Any programming language (except Assembly), software or extra hardware is fine.

Thanks!

Community
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dylanigan
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4 Answers4

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Go to ebay, get any cheap wireless transmitter in 430Mhz range, connect it to the serial port and have fun. It's like wireless serial port -- whatever you send from one end, will appear on the other, and vice versa.

From my experience, you should avoid any transmitters that cost less than $10, or you may need to implement a heavy garbage filtering software scheme. If you prefer your data nice and clean, stick with something like CC1101-based transmitters. Sometimes these are sold in pairs -- just exactly what you need.

And, finally, choose wisely. Transmitters come in 5V and 3.3V varieties. Most probably you need the latter for your RaspberryPi to match GPIO voltage levels.

lenik
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This may be cheating, but you could use a Zigbee to communicate between Raspberry Pis. There is already a simple add-on for the Raspberry Pi!

The well written documentation for communicating between the Pis are here. You can also find out a bit more about this topic on the Raspberry Pi forums.

syb0rg
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    zigbee is very expensive in terms of money as well as the power consumption, and it's hardly necessary to use 200kbps module to transmit 100 bytes once a second. – lenik Oct 02 '13 at 04:48
  • @lenik I agree it's not optimal, but it fits the OP's specification. Also, they aren't as expensive as they use to be, you just have to buy the right thing from the right place. – syb0rg Oct 02 '13 at 12:03
  • Yes, I went with 2 xbees. They are working perfectly! Thanks! – dylanigan Nov 02 '13 at 12:41
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Have you looked at the XBee wireless module?

STEJ
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    Adafruit has everything you need to get started at much cheaper prices than the first site I recommended. http://www.adafruit.com/category/29 – STEJ Oct 02 '13 at 10:51
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From a simplicity standpoint I would go with a tiny USB Wifi module on each RPi and connect that way. (Direct connection either with an Ad Hoc network or have one configured as a Access point). The cost is almost the same as a non-wifi RF solution.

If you really want a non-Wifi option you could go with a transmitter/receiver pair. But be aware that those are one-way links so you will need 2 pairs for bi-directional communication.

You will also need to write robust error correcting protocols to handle interference.

Craig
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