Zigbee Networking and Data Transmission

Before reading the article, if you are not fresh to Zigbee knowledge, you may please read the other artical”General Introduction about Zigbee”.

zigbee communication networks

Zigbee network is usually comprised of 3 kinds of nodes as below:

  • Router: The router is used to transmit and receive data. Meanwhile, router can keep net to distribute address for later joining nodes.
  • Coordinator:  coordinator is used to create a Zigbee network and distribute address for initial joining nodes. Each Zigbee network only needs one coordinator.
  • End Device: End devices are usually low power consumption powered by battery and only send data periodically. Or control sleeping or working of nodes by related key

Note: when the PANID of 3 nodes are the same, it can be network and communication  without  related operation by people. This can  distinguish the Zigbee network by set PANID. In an area, multi- Zigbee networks can be co-existed and don’t interfere each other.

Zigbee module’s adderss has 64 bit address,also called as IEEE address.  The 64 bit address of each Zigbee module is determined by CPU of module. CPU manufacturers ensure global uniqueness of 64 bit address in the world. And 16 bit address is also called short address or 16-bit ID, which is automatically got after Zigbee module joining network. Before joining the network, its Zigbee module address is 0xFFFE 16-bit address. In this network, the 16-bit address is uniqueness which can be used as data communication address,but after network reset, the 16-bit address will be changed.

Data Transmission of Zigbee Module

After power ON, Zigbee module will automatically make network.

At the terminal of coordinator, send data by serial port and all of routers can receive data;  at a terminal of a router, send data by serial port, buy only coordinator can receive it.  Sending data and receiving data are consistent, clear transmission mode, each data contains Max length of 80 bytes.

Note: The default of router are to send data to coordinator; user can change data sending way of router to broadcast way by set command. This can make all of Zigbee device to receive data in a network.

Typical Data Communication of RS485 Port

Typical  RS485 network is usually comprised of a main unit ( PC, PLC, Controller,etc) and multi-device of data gathering or performing. The main unit sends command to secondary devices by MODBUS-RTU way.

Recently, we have changed wire temperature and humidity gathering system to wireless Zigbee network. And the following is simple notes:

System combination:  serial port( RS485) and MODBUS-RTU protocol

Serial port settting: 9600-8-N-1

1)Connect a Zigbee module to main unit( or USB DONGLE, or Zigbee-TCP/IP gateway), set Coordinator, baud rate=9600

2)Connect Zigbee module to each secondary devices(by RS485 port), set Router, baud rate=9600

3) Changing completed and no need to change software

A. If PC is main unit, the wiring diagram is as below:

PC Zigbee

B. If  PLC as main unit, the wiring diagram is as below:

RS485 Zigbee

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