zigbee and xbee

8/4/2019 ZigBee and XBee

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802.15.4 ZigBee Physical Layer

ZigBee is a wireless technology developed as an open global standard to

address the unique needs of low-cost, low-power wireless M2M networks.The ZigBee standard operates on the IEEE 802.15.4 physical radiospecification and operates in unlicensed bands including 2.4 GHz, 900MHz and 868 MHz.

The 802.15.4 specification upon which the ZigBee stack operates gainedratification by the Institute of Electrical and Electronics Engineers (IEEE) in2003. The specification is a packet-based radio protocol intended for low-cost, battery-operated devices. The protocol allows devices tocommunicate in a variety of network topologies and can have battery lifelasting several years.

The ZigBee specification is a combination of HomeRF Lite and the802.15.4 specification. The spec operates in the 2.4GHz (ISM) radio band -the same band as 802.11b standard, Bluetooth, microwaves and someother devices. It is capable of connecting 255 devices per network. Thespecification supports data transmission rates of up to 250 Kbps at arange of up to 30 meters. ZigBee's technology is slower than 802.11b (11Mbps) and Bluetooth (1 Mbps) but it consumes significantly less power.

ZigBee/IEEE 802.15.4 - General Characteristics:

Dual PHY (2.4GHz and 868/915 MHz) Data rates of 250 kbps (@2.4 GHz), 40 kbps (@ 915MHz), and 20 kbps (@868 MHz) Optimized for low duty-cycle applications (


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Application/external stimulus defined rate (e.g., lightswitch) Repetitive low latency data

ZigBee protocol features include:

Support for multiple network topologies such as point-to-point,point-to-multipoint and mesh networks

Low duty cycle provides long battery life

Low latency

Direct Sequence Spread Spectrum (DSSS)

Up to 65,000 nodes per network

128-bit AES encryption for secure data connections

Collision avoidance, retries and acknowledgements

Mesh NetworksA key component of the ZigBee protocol is the ability to support meshnetworking. In a mesh network, nodes are interconnected with othernodes so that multiple pathways connect each node. Connectionsbetween nodes are dynamically updated and optimized throughsophisticated, built-in mesh routing table.

Mesh networks are decentralized in nature; each node is capable of self-

discovery on the network. Also, as nodes leave the network, the meshtopology allows the nodes to reconfigure routing paths based on the newnetwork structure. The characteristics of mesh topology and ad-hocrouting provide greater stability in changing conditions or failure at singlenodes.


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There are wide range of networking solutions based on the ZigBeeprotocol. XBee and XBee-PRO modules and other XBee-enabled devicesprovide an easy-to-implement solution that provides functionality toconnect to a wide variety of devices.

XBee/XBeePRO OEM RF Modules

The XBee and XBee-PRO OEM RF Modules were engineered to meet IEEE802.15.4 standards and support the unique needs of low-cost, low-powerwireless sensor networks. The modules require minimal power andprovide reliable delivery of data between devices. The modules operatewithin the ISM 2.4 GHz frequency band and are pin-for-pin compatible with

each other


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Features:

AT and API Command Modes for configuring module parameters

Extensive command set

ISM (Industrial, Scientific & Medical) 2.4 GHz frequency band

Indoor/Urban Range up to 100 ft. (30 m) Up to 300 (100 m)

RF Data Rate 250,000 bps 250,000 bps

Serial Interface Data Rate (software selectable) 1200 - 115200 bps(non-standard baud rates also supported) 1200 - 115200 bps (non-standard baud rates also supported)

16 Direct Sequence software selectable Channels


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Pin Configuration

Communication ModesThe XBee supports both an AT and an API (Application ProgrammingInterface) mode for sending and receiving data at your controller. Bothhave their advantages.AT ModeIn AT Mode, also called Transparent Mode, just the message data itself issent and received. The protocol link between the two is transparent to theend user and it appears to be a nearly direct serial link between the nodesas illustrated previously in Figure 1-4. This mode allows simpletransmission and reception of serial data. AT Commands are used to

configure the XBee, such as to send the data to a node with an address of5: ATDL 5.


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API ModeIn API Mode, the programmer packages the data with needed information,such as destination address, type of packet, and checksum value. Also,the receiving node accepts the data with information such as sourceaddress, type of packet, signal strength, and checksum value. The

advantages are the user can build a packet that includes important data,such as destination address, and that the receiving node can pull from thepacket information such as source address of the data.While more programming intensive, API Mode allows the user greaterflexibility and increased reliability in some cases.

Typical Microcontroller Interfacing to the XBee

By default the XBee module starts in Transparent mode. Everything sendserially to the base XBee module is received on the remote XBee module

if the remote module remains in Transparent mode.

Command used to enter API mode


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There are total of 10 API commands. Every API begins with 0X7E.

Structure of an API command


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Examples

Command to configure DIO0 of remote module as analog input

Command to set PWM0 to 50% duty cycle

In API mode we should either use a 64-bit address transmit request or 16-bit address transmit request to send serial data to a remote XBee module.

Command to send the ASCII string HELLO WORLD to the remotemodule


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The ZigBee operates in the 2.4GHz (ISM) radio band.

The specification supports data transmission rates of up to 250 Kbpsat a range of up to 30 meters.

It is capable of connecting 255 devices per network.

The XBee module uses a fully implemented protocol for datacommunications that provides features needed for robust networkcommunications in a wireless sensor network (WSN).

The XBee supports both an AT and an API (Application ProgrammingInterface) mode for sending and receiving data at your controller.

In AT Mode, also called Transparent Mode, just the message dataitself is sent and received.

In API Mode, the programmer packages the data with neededinformation, such as destination address, type of packet, andchecksum value.

By default the XBee module starts in Transparent mode


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zigbee and xbee

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