Xbee

The XBee is a Radio Frequency (RF) module compliant with the IEEE 802.15.4 standard providing low-cost, low-power wireless network solutions.






Zigbee and the 802.15.4 standard

Zigbee Wireless Standard refers to a suite of high level communication protocols that add mesh networking functionality to the 802.15.4 standard.

802.15.4 is a WPAN (Wireless Personal Area Network) standard that defines the lower layer specifications (PHY layer and MAC sublayer) for low cost, low data rate, low power consumption networking.

If unfamiliar to you, take a minute to brush up on the OSI Model. Here is a rough idea of communication between layers: The Network Layer (handles network configuration, security, routing and deliver of data) issues requests to the Data Link Layer (LLC and MAC) that the MAC sublayer (handles physical addressing and provides access to the physical channel) communicates to the PHY layer (contains the RF tranceiver and translates packet data into an electrical signal).

Download this pdf for a more detailed explanation of the Zigbee and IEEE 802.15.4 standard.






So what is the difference between XBee Series 1 and XBee Series 2?

A good place to start is to read Digi's explanation between the XBee Series 1 and Series 2.

To reiterate, the XBee Series 1 (XBee and XBee-PRO 802.15.4) and XBee Series 2 (XBee and XBee-PRO ZNet 2.5) are pin-for-pin compatible, meaning that the layout of their pins are identical so your circuit will be exactly the same. Series 1 and Series 2 modules use different chipsets, however, so they are wirelessly incompatible and can not communicate with eachother. Series 1 employs the Freescale chipset and supports peer-to-peer (unicast ) and broadcast (multicast) applications, while the Series 2 module employs the Ember chipset and additionally supports zigbee network formation.

Demystifying 802.15.4 and ZigBeeŽ is a short, aptly named white paper that I highly recommend reading.






802.15.4 Topologies

Zigbee Topologies

Serial Terminal Programs

screen: Terminal program on the Mac (or Linux)
HyperTerm: Windows Start Menu, Accessories, Communication
X-CTU: Terminal emulation
Z-Term: http://homepage.mac.com/dalverson/zterm/
amongst others





Setting up ZTerm

ZTerm is a terminal emulation program for the Macintosh that allows you to monitor and talk over the serial port.

You can download ZTerm here: http://homepage.mac.com/dalverson/zterm/

If you are using a USB to Serial adapter you will need to install the appropriate driver to enable ZTerm to recognize it as a serial port.

Once ZTerm and driver are happily installed, plug in the USB cable connecting your XBee circuit to your computer and launch ZTerm.

When ZTerm opens you should encounter a window like the one on the left. If you encounter an error similar to the window on the right, ZTerm did not open the serial port successfully and you will likely need to adjust your ZTerm Settings.

Under Settings --> Connection set the Data Rate (Baud Rate) to 9600, Data Bits to 8, Stop Bits to 1 and set Parity to None. Turn on Local Echo and uncheck Flow Control.

Under Settings --> Modem Preferences select your Serial Port from the drop down menu.


ZTerm should now be set up to talk to your XBee serially.