Wednesday, September 16, 2009

Details of X-CTU

The MaxStream X-CTU software, which is also a free download from the MaxStream site, allowed you to use your personal computer to program the XBee modules serially using the XBee DIN,DOUT,RTS, and DTR pins.

X-CTU even provides a built in RS 232 terminal emulator. As we can see in capture below, key register values can be changed within the X-CTU windows and written to the XBee modules mounted on the XBee interface boards. The COM10 XBee module as the coordinator and the COM X XBee module as an end device by setting the XBee modules CE (Coordinator Enable) register to a 1 and 0 (zero) respectively.Assigned a PAN ID of 0xCAFE in the coordinator X-CTU window. The XBee can run in one of three MAC modes:
1) 802.15.4 + Maxstream Header
2) 802.15.4 without ACKs
3) 802.15.4 with ACKs

Monday, September 14, 2009

Wireless Personal Area Network (WPAN)

A personal area network (PAN) is a computer network used for communication among computer devices close to one's person. The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters. PANs can be used for communication among the personal devices themselves , or for connecting to a higher level network and the Internet.

Personal area networks may be wired with computer buses such as USB and FireWire. A wireless personal area network (WPAN) can also be made possible with network technologies such as IrDA, Bluetooth, UWB, Z-Wave and ZigBee.

A WPAN (wireless personal area network) is a personal area network - a network for interconnecting devices centered around an individual person's workspace - in which the connections are wireless. Typically, a wireless personal area network uses some technology that permits communication within about 10 meters - in other words, a very short range.

A key concept in WPAN technology is known as "plugging in". In the ideal scenario, when any two WPAN-equipped devices come into close proximity (within several meters of each other) or within a few kilometers of a central server, they can communicate as if connected by a cable. Another important feature is the ability of each device to lock out other devices selectively, preventing needless interference or unauthorized access to information.Proposed operating frequencies are around 2.4 GHz in digital modes.

By wikipedia.org

Thursday, September 10, 2009

ZigBee Network Topologies

The way that a message is routed from one network node to another depends on the network topology. A ZigBee network can adopt one of the three topologies: Star, Tree, Mesh. These are illustrated on the right and briefly described below.

Star Topology

A Star network has a central node, which is linked to all other nodes in the network. All messages travel via the central node.

Tree Topology

A Tree network has a top node with a branch/leaf structure below. To reach its destination, a message travels up the tree (as far as necessary) and then down the tree.

Mesh Topology

A Mesh network has a tree-like structure in which some leaves are directly linked. Messages can travel across the tree, when a suitable route is available.

Wednesday, September 9, 2009

Communicate Between Two XBee Devices

Before going further,the first step to understand in XBee operation is trying to communicate it between each other (TX-RX) in bidirectional mode..I need to install the driver at 2 PC's which is USB Serial Converter and USB Serial Port..This is to make the XBee compatible with the PC's..After that the X-CTU software need to be installed.

This software will enable user to send and receive a data at a time.The are several configuration need to be determine first such as the Baud Rate = 9600, data bits=8 and stop bits = 1..After that, we must enter the command mode by typing +++ into the terminal area and after that the Xbee's are ready to be operated..The simple diagram on how the XBee communicate is shown below.

But there is a bit problem on communicate the XBee's..The another XBee modules can't be detected by PC..It said "Unable to communicate with the moderm"..This happened at one side only..In my opinion there is something wrong either the hardware or the driver..

Monday, September 7, 2009

ZigBee Devices (FFD & RFD)

The IEEE 802.15.4 specification identifies two devices which is FFD and RFD. The 802.15.4 Full Function Device (FFD) is literally able to do it all. A FFD network will be powered from an inexhaustible power source, which is called out as an AC-fed mains supply, as it must always be active and listening on the network, among other things.
An RFD (Reduced Function Device) perform on recording temperature data, monitoring switches or controlling external devices. The power source of RFD is easily exhaustible and by that RFD is prone to sleep most of the time.
The ZigBee end device can be either an FFD or RFD depending on the application. A ZigBee router is an FFD that enables the extension of the physical range of a ZigBee network. It is used to allows more nodes to join the network as the radio range of the root ZigBee network is effectively increased. The router also can be functioning as a end devices.

Wednesday, September 2, 2009

IEEE 802.15.4

ZigBee is officially a wireless network protocol that is designed to be used with low-data-rate sensor and control networks. ZigBee can also eliminate the need to string wires all over the place as it can easily reach data rates comparable to and above standard RS-232 and RS-485 wired protocols. Although an IEEE 802.15.4 network can easily obtain RS-232 speeds, you wont see many battery powered applications of IEEE 802.15.4 networks replacing RS-232 communication links,especially if the traffic on the IEEE 802.15.4 based pseudo RS-232 link is heavy.



ZigBee is a standards based network protocol supported solely by the ZigBee Aliance that uses the transport services of the IEEE 802.15.4 network specification. The IEEE 802.15.4 specification also uses internal layers, which are normally referred to as sublayers. The wireless 802.11b specification and the wired 802.3 specification also employ the concept of sublayers. The IEEE 802.15.4 specification calls out a pair of 802.15.4 sublayers, the PHY and the MAC.

If we relate the IEEE 802.15.4 sublayers to the ZigBee protocol stack, the ZigBee PHY sublayer, which is actually the IEEE 802.15.4 PHY sublayer, is all about the radio and the generation of the radio link. A ZigBee stacks PHY responsibilities include receiver energy detection, link quality indication and clear channel assesment. The ZigBee stacks PHY is also primarily responsible for transmitting and receiving packets across the magnetic medium. The ability to sniff the air for other nodes is very important in the ZigBee and IEEE 802.15.4 world as this is what is done to determine if a new ZigBee or IEEE 802.15.4 network can be spawned.