What is a good communicaton device among teensy and arduino besides "XBees"

Question

I have been using XBees to communicate my teensies so far. However, as you know, XBees are really expensive and when I want multiple devices to communicate with each other, I have to pay for several teensies + several XBees, which come up to be more than 200 dollars.

Also, An XBee is for between two designated teensies. I want all of my teensies to communicate with each other

1. Is there any communication device out there that I can hook up to multiple teensies or arduinos at once without buy as much XBees?

2. Or what is a communication device that lets everything within the range to communicate with each other?

3. Or any other way to let them communicate without using individual teensies?

If you can answer any of them, please help me out!!

Answer 1

What about using 'dumb' rf transceivers and building a protocol on that?

RFM12Bs or even something cheaper.

Answer 2

I would look into using other wireless modules. XBees are nice, but are indeed expensive. I posit that you probably aren't using all of the options they provide in your projects anyways. Things like mesh networking are AMAZING, but aren't usually strictly necessary for most projects.

A very cost effective option, while still retaining some error checking, is to use IC's by Nordic, esp. the nRF24 series. There is an excellent arduino library for these modules that most likely can be ran on the Teensy with minimal adaption, especially if you are using the Teensyduino. This library also allows for some mesh communication (obviously not as robust as the XBees); see here (http://maniacbug.github.com/RF24/starping_relay_8pde-example.html).

If you order non-amplified versions of these modules, they can be had for under $7 per module. Here are some for $5.50 each. Amplified versions are in the range of $15-$20, so if node to node distance is greater than about 40 ft the cost effectiveness compared to XBees goes down dramatically. It all depends on your usage.

From the same store that had the cheap Nordic modules, there are some cheap bluetooth modules that might be worth looking into; these have caveats in that they are meant to be connected to by a computer (a master unit) rather than each other (slave units). You can buy a master Bluetooth module for about $20 from ITeadStudio though.

Alternatively, the XBee CAN be used without a microcontroller for simple sensors and other uses. Then your cost is much lower per unit, around $25 instead of $25 + $16. See "Building Wireless Sensor Networks: with ZigBee, XBee, Arduino, and Processing" by O'Rielly for more details.

Answer 3

I use the HopeRF RFM12B transmitters. They are the same ones used in Jeenodes, and there are already communication libraries from Jeenode that work just fine with any Arduino-like board.

They are substantially cheaper than the Xbee. They also come in both 3.3 and 5v versions, which can communicate between each other. I believe the manufacture has discontinued the 5v ones, but you can still find them around.

The only thing I don't like about them is the 2mm pin spacing, since you can't just drop them into a bread board or strip board. However, if you do try using them, I recommend getting some laptop IDE cables - they have 2mm spacing and can be cut to fit the RFM12 nicely to use it in a breadboard.

Answer 4

I use the Asus WL-520GU WiFi router with USB. You can often find a rebate program to bring the net price to $30 or so.

The router has a USB for connection to the teensy and is a full WiFi router. You can load DD-WRT on it. An example config.

And, as a bonus, the router will power your teensy through the USB connection.

Downsides: it's much larger than an xbee module or similar.