N1VAN

Here’s a tutorial that will round-out your understanding of ZigBee wireless communications (translated). The protocol is great for hobby electronics projects because it uses low-power short range wireless devices to build a mesh network. The guide covers both hardware and software, but also takes the time to explain what that hardware is doing in the background. As you can see, several different renditions of an XBee module are used as examples. They pretty much all rely on a series of SparkFun breakout boards that each serve different purposes. Once you’ve acquired these modules, there’s a fair number of choices needed to configure them to play nicely with each other. We read most of the tutorial (we’ll save the rest for later enjoyment) and had no problem following along even without owning the hardware or being able to use the interface as we learned. Whenever we cover XBee modules we always like to mention that it’s quite easy to use these for remote sensors with no additional microcontroller needed: [Jody] wanted to know when his garage door was open.

Here is another option for getting your Arduino (or other PIC) connected to your network (ethernet) - use an old NSLU2!

The NSLU2 and Arduino both talk TTL, but the NSLU2 is 3.3v and Arduino is 5v. Simple fix - add a resistor!

Only 3 wires are required - pins 2, 3 and 4 on the NSLU2. You do not want to connect the power pin. Per the table below, look for the white stripe - that is the power pin.

NSLU2 - pin-out of the J2 serial port

Pin 1 - 3.3v, pin 1 has a white stripe next to it

Pin 2 - RXD, receive from Arduino to NSLU2 (must have resistor)

Pin 3 - TXD, transmit from NSLU2 to Arduino

Pin 4 - GND, ground connection

This article is written in reference to the "Freeduino" - a BBB (bare bones board) type. Make sure everything is powered off and unplugged. Then, connect the TTL pins labeled "RX", "TX" and "GND" on the BBB to the proper pins on the NSLU2. The 4 serial port TTL pins on the NSLU2 are visible just below the battery to the right.

You must place a 10k resistor between the Arduino and the NSLU2 on pin 2 of the NSLU2 so the 5v coming from the Arduino are reduced to safe levels.

Now power up the Arduino and NSLU2 that is flased with Debian (SlugOS should work also). Install minicom (apt-get) and start up minicom and set the serial port to ttyS0, 9600, 8N1.

If the connections are correct, the TTL pins/port on the Arduino and NSLU2 are functional you should now see the output from the Arduino. If you do not see anything, be sure you have pre-programmed your Arduino with a program that outputs text at the proper baud rate. Also try powering off both units, power back up and try again. If you have made other hardware mods such as overclocking on the NSLU2, it is possible the serial port will not work. You must place a 10k resistor between the Arduino and the NSLU2 on pin 2 of the NSLU2 so the 5v coming from the Arduino are reduced to safe levels.

I am using some Arduino (freeduino BBB) units to monitor temperature, humidity and other sensor inputs for an HVAC project.

I needed a way to communicate with the unit, allowign it to send data and to send it commands.

I did not want to rely on the serial port, as that means a computer on the other end - if that computer fails (reboots, powers off), it would ultimately reset the arduino when the serial port opens again.  Also, I want to keep as much logic within the unit itself for the same reason.  The main reason for sending data out is for data logging and analysis.  If I loose a little data, no big deal, as long as the unit itself is doing it's job reliably.

I looked in to ZigBee, XBee, PC-Net and other ethernet shields/chipsets.   There are also various 'serial to ethernet' adapters / bridges.  The main issue with these is cost.   Just to get 2 units connected - one unit with the sensors, the other connected to a computer to send/receive data - it would cost approximately $50.00, is several configurations more than that.

So, I found some RFM12 units on ebay for less than $30 for THREE.   They were fairly easy to wire up, code is straightforward, and they work well.

Look at the readme at this url, there is also a sample arduino sketch:

http://code.jeelabs.org/libraries/RF12/examples/RF12demo/

The readme will have additional links to get info on how these work.

This is a great idea for a mobile antenna - made from steel rod, lexan, suction cups and a few other items, it is a very inexpensive design, and has impressive J-Pole like performance.

Full story and instructions HERE.

--</