SparkFun Forums

[hcker2000]

For $4 you can get a 433Mhz or 915Mhz RFM12B transmitter/receiver. With proper programming you could then create a very simple peer to peer network, polling or time slicing. These modules or pretty sophisticated and if you Google them you can see some people playing with simple network protocols for them.

For no money you can simply implement manchester encoding yourself with those cheap rf transmitter/receivers you already have or 2byte -> 3byte encoding in software and skip the hardware encoder/decoder all together.

For the cheap modules I had a simple 2byte -> 3byte scheme written for my microcontroller based on white paper source code from radiotronix. Then I replaced it with code from an Arduino library called VirtualWire. It's an Arduino library, but if you google it, you can find the C source code and it's easy to adapt to any uC, all you need to do is attach it to a hardware timer set to 8x your required bitrate.

More good info. Thanks. Have you ever done any thing with the multi-transmitter and single receiver setup?

[TheDirty]

The only thing I have with the those regular cheap rf modules is a single transmitter and receiver. Other than all the silly test setups I have, the only practical thing I'm doing is using one as a remote for my gas fireplace.

I've really turned to using those RFM12B modules. From the manufacturer they are pretty cheap, they have a bunch of nice, more advanced features, but not crazy like a TI CC1101 or anything. If you want samples in singles, futurelec has them in the dual row pin configuration. If you get them from Futurelec they are twice the price at $8 each, but you can get them in singles. These things are seriously pretty small. I was pretty amazed when they got here.

I started playing with MSP430's and I'm trying to make a really stripped down network protocol that will handle really simple nodes. I just got started on this a short while ago. It will be a simple time sliced multi node, single master protocol; no mesh.

http://www.higginstribe.com/msp430/rf-n ... st-001.jpg

[hcker2000]

Man those are nice and small. Where would you recommend to buy a matched tx/rx pair? That way I can start messing around with them.

[hcker2000]

Here is a good link for a tutorial on the RFM12B

http://blog.strobotics.com.au/2008/01/0 ... ial-part1/

[cpolley]

Multiple TX to one RX: I have done exactly that, and it certainly works. Sharing one channel is a challenge but it's possible. I regret doing it with these units though, and I seriously recommend thinking about spending the extra on something like the nordic or xbee units. I just found the 434 units were completely unreliable in their reception no matter what I did.

Actually I also used the holtek encoders/decoders to start with. If you already have a micro in the circuit then don't bother with them, just use the micro UART.

In any case I'd be glad for someone to profit from my long and painful experience with these things, so drop me a line if you have questions about how to go about it
(craig dot polley at g mail)

[mcuaust]

hcker2000,
there's a related thread at http://www.arduino.cc/cgi-bin/yabb2/YaB ... 812591/4#4.

Read what 'novice' wrote. He found an article that shows you can use the cheapie units (as others have stated in this thread at SFE).

"I found an article on on/off keying (OOK) to help you. It's titled "Wireless Monitoring System" and regards a system very similar to your's.
find at http://www.circuitcellar.com/library/pr ... ti-167.pdf"

Have fun, and report back your results.