Yiwen takes you to know ZigBee

1、 Internet of things communication protocol

Common short-range wireless communication protocols

Internet of things communication protocol

Access mode - Cloud protocol

Support TCP/IP Internet of things devices , Can pass WIFI、 Cellular network and Ethernet , Use HTTP、MQTT、CoAP、LwM2M as well as XMPP And other application layer protocols to access the cloud .

Access mode - Gateway Protocol

Gateway protocol is a protocol applicable to short-range communication that cannot be directly connected to the cloud , Like Bluetooth 、ZigBee、LoRa etc. .

This kind of equipment needs to be switched by the access gateway , adopt TCP/IP The agreement goes to the cloud .

2、Zigbee Protocol Brief

One 、Zigbee history

ZigBee, The name comes from the way bees use to survive and develop ： Bees jump Zig-Zag Dance of shapes to share the location of newly discovered food sources , Information such as distance and direction .

ZigBee The predecessor was 1998 Year by year INTEL、IBM And other industrial giants “HomeRFLite” technology .

2002 In the second half of , The British Invensys company 、 Mitsubishi Electric Co., Ltd 、 Motorola of the United States and Philips semiconductor of the Netherlands jointly announced their alliance “Zigbee union ”, The name of the research and development is “Zigbee” Next generation wireless communication standard .

Zigbee And IEEE 802.15.4

ZigBee It is an open system based on IEEE 802.15.4 Protocol wireless personal area network (Wireless Personal Area Networks) standard .

IEEE 802.15.4 The physical layer and media access control layer are defined , and ZigBee It defines higher layers such as network layer and application layer .

ZigBee Technical characteristics

1. low power consumption ： because ZigBee The transmission rate is low , The transmitting power is only 1mW, And sleep mode , Low power consumption , therefore ZigBee The equipment is very power-saving . It is estimated that ,ZigBee The equipment only relies on two sections 5 The No. 1 battery can last for up to 6 Months to 2 About years of use .
2. Low cost ： because ZigBee The complexity of the module is not high ,ZigBee The agreement is royalty free , Plus, there's no charge for the frequency band used , So it costs less .
3. Time is short ： The communication delay and the activation delay from the sleep state are very short , Typical search device delay 30ms, The delay of sleep activation is 15ms, The delay of channel access of active equipment is 15ms.
4. Large network capacity ： A star shaped structure ZigBee The network can hold up to 254 One slave and one master , A region can have up to 100 individual ZigBee The Internet , And the network composition is flexible . Reticular ZigBee There may be... In the network 65000 Multiple nodes .
5. reliable ： Collision avoidance strategy is adopted , At the same time, a special time slot is reserved for the communication services requiring fixed bandwidth , Avoid the competition and conflict of sending data .MAC The layer adopts the data transmission mode of full confirmation , Each sent packet must wait for the receiver's confirmation message . If there is a problem during transmission, it can be retransmitted .
6. Security ：ZigBee Cyclic redundancy check (CRC) Packet integrity check function , Support authentication and authentication , Adopted AES-128 Encryption algorithm , Each application can flexibly determine its security attributes .

ZigBee Some members of the Alliance

Two 、Zigbee Device type

ZigBee There are three types of devices in wireless sensor networks ： The coordinator 、 Router 、 Terminal nodes

1、ZigBee The coordinator （Coordinator）

It contains all the network information , yes 3 The most complex of the devices , Large storage capacity 、 The strongest computing power .

It is mainly used to send network beacons 、 Build a network 、 Manage network nodes 、 Storage network node information 、 Find the routing information between a pair of nodes and continuously receive information .

Once the network is established , The coordinator acts like a router node .

2.ZigBee Router （Router）

The functions it performs include allowing other devices to join the network , Hop routing , Communication of battery powered terminal under auxiliary subtree .

3.ZigBee Terminal equipment （End-device）

A terminal device has no specific responsibility for maintaining the network device , So it can sleep and call , Look at its own choice .

So it can be used as a battery powered node .

3、 ... and 、ZigBee Network topology

Device type and topology relationship

ZigBee Reticular （MESH） The Internet

Four 、ZigBee Network building - Coordinator the process of building a new network

1、 Detect coordinator

The node must have two conditions ：

1. have ZigBee Coordinator function ,
2. Not joined other networks .

Any process initiated by a node that does not meet these two conditions to establish a new network will be terminated by the network layer management entity

2、 Channel scan

Channel scanning includes energy scanning and active scanning .

3、 Configure network parameters

The network layer management entity will select one for the new network PAN The descriptor , Must satisfy PAN Descriptor is less than or equal to 0x3fff, It's not equal to 0xffff, And is unique within the selected channel PAN The descriptor

4、 Run the new network

5、 Allow devices to join the network

Only ZigBee Coordinator or router can pass through NLME_PERMIT_JOINING.request Primitive to set the node in a state that allows the device to join the network .

ZigBee Network building - Nodes join the network

1） adopt MAC Layer Association join the network

2） Join the network by connecting to the previously specified parent node

adopt MAC Layer Association join the network

1. A child node initiates a channel scan
2. Child nodes store each PAN Information
3. Child node selection PAN
4. Child node selects the parent node
5. Child node requests MAC relation
6. Parent node response MAC relation
7. The child node responded that the connection was successful
8. The parent node responded that the connection was successful

The networking operation is realized by the protocol stack .

5、 ... and 、ZigBee Application field

1. Consumer electronics
2. Home and building automation equipment
3. Industrial control devices
4. Agricultural automation
5. computer peripherals
6. Medical sensors
7. Toys, game consoles and other equipment
8. Support a small range of wireless communication based control and automation

3、Zigbee Protocol stack

ZigBee The protocol stack has many versions , From different manufacturers ZigBee There are some differences between protocol stacks .

Although the agreement is uniform , However, the specific implementation form of the protocol changes , That is, the protocol stacks provided by different manufacturers are different

1. There are differences between function names and parameter lists
2. Learn from the manufacturer Demo Demo program and documentation learning

Zigbee Protocol stack use

Use ZigBee The basic idea of protocol stack development can be summarized as the following three points ：

1. User for ZigBee The development of wireless network is simplified to that of application layer c Language program development , There is no need to delve into complex ZigBee Protocol stack ;
2. ZigBee Data acquisition in wireless sensor networks , Users only need to add the sensor reading function in the application layer ;
3. If energy conservation is considered , It can be timed according to the data acquisition cycle , Wake up when the time comes ZigBee The terminal node of , After the terminal node wakes up , Automatically collect sensor data , Then send the data to the router or directly to the coordinator .