Z-Wave Network Setup PDF

Learning Outcomes Install up to five common control devices such that they communicate through radio frequency correctly Describe that every automation system device has a unique identity Unit 2.4 | Z-Wave Network Setup 105  2.4.1 De...

Learning Outcomes Install up to five common control devices such that they communicate through radio frequency correctly Describe that every automation system device has a unique identity Unit 2.4 | Z-Wave Network Setup 105  2.4.1 Device Identity: Z-Wave Networks, Nodes and Devices A network consists of at least two nodes (also known as devices) that communicate with each other via a physical communication medium, such as a cable. As radio is wireless, its communication medium is the air, which is the same medium for mobile phones, television and other technology. Each type of network has a specific protocol that excludes messages from other radio sources and allows the different nodes in the network to identify one another. Each node in the network has a unique identification (ID) to distinguish it from other nodes in the same network. Z-Wave defines two types of ID for the organisation of the network: The home ID is the common identity of all nodes belonging to one logical Z-Wave network. It has a length of 4 bytes (32 bits). The node ID is the address of a single node in the network. It has a length of 1 byte (8 bits). While nodes may have similar node IDs, those with different home IDs cannot communicate with one another, as the two networks are isolated from each other. No two nodes in the same network (i.e., with the same home ID) can have identical node IDs. This means that each node can be individually addressed. There are two basic types of Z-Wave devices: controllers, which control other Z-Wave devices; and slaves, which are controlled by other Z-Wave devices. Controllers are factory programmed with home IDs that users cannot change. Slaves do not have pre-programmed home IDs, as they take on the home IDs that the network assigns them. The primary controller assigns other nodes their own home IDs to add them to the network. If a node accepts the primary controller’s home ID, this node becomes part of the network. The primary controller also gives an individual node ID to each new device that is added to the network. This process is known as inclusion. Table 2.4-1 summaries the key differences in home and node IDs of controllers and slaves. Table 2.4-1: Home and node IDs of controllers and slaves Type of Z-Wave Device Controller Slave Home ID The home ID is already The network assigns a (The common identity of a Z-Wave network) set as the factory default. home ID. Node ID The controller has its The primary controller (The individual identity (address) of a node own predefined node ID assigns a node ID. within a common network) (typically 0x01). Unit 2.4 | Z-Wave Network Setup 106  2.4.2 Example of a Z-Wave Network The network shown in Fig. 2.4-1 has two controllers with a factory-default home ID and two other slave devices that have no assigned home ID. (a) Before Inclusion Fig. 2.4-1: Z-Wave devices before inclusion in a network Depending on the controller used to configure the Z-Wave network, the network home ID in this example will be either 0x00001111 or 0x00002222. Both controllers have the same node ID of 0x01, and at this stage, the slave devices have no node IDs assigned to them. Fig. 2.4-1 shows two networks having one node. Because the nodes have no common home ID, they cannot communicate with each other. One of the two controllers is now chosen as the network’s primary controller. This controller assigns its home ID to all the other devices and gives each of them an individual node ID. Unit 2.4 | Z-Wave Network Setup 107 (b) After inclusion Fig. 2.4-2: Z-Wave devices after inclusion in a network When inclusion is successful, all nodes have the same home ID and are thus connected to the same network. Each of them also has a unique node ID, which allows them to be individually identified and to communicate with each other. Fig. 2.4-2 shows two controllers. The controller whose home ID becomes the home ID for all devices is called the primary controller. The other controller is the secondary controller. The primary controller can include additional devices while the secondary controller cannot. However, in all other respects, the primary and secondary controllers work in the same way. Because the nodes of different networks have different home IDs and cannot communicate with each other, they can coexist but cannot “see” each other (Fig. 2.4-3). Fig. 2.4-3: Two coexisting Z-Wave networks with different home IDs Unit 2.4 | Z-Wave Network Setup 108  The 32-bit home ID can define up to four billion (232) different Z-Wave networks, each having a maximum of 256 (28) different nodes. However, as the network assigns some of these nodes for internal communication and special functions, a Z-Wave network can only support a maximum of 232 devices. (c) Exclusion Nodes can be removed from a Z-Wave network. This process is called exclusion, which deletes the home ID and the node ID from the device to be removed. The removed device is reset to its factory default state (controllers have their own home ID while slaves have none). Unit 2.4 | Z-Wave Network Setup 109