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Learn how to create software bindings and configure LonWorks networks, including variable bindings for sharing control information between function blocks or nodes. Explore commissioning methods and network management tools for efficient programming.
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Chapter 7 LonWorks Network Programming LonWorks Network Programming • Network Variable Bindings • Device Commissioning
LonWorks network programming involves making the software bindings that represent the interactions between the physical nodes.
Network management tools may use a variety of interfaces for programming and configuring LonWorks networks.
Ad hoc program design requires the network management tool to be connected to the nodes because they are commissioned as they are added to the network program.
Engineered program design allows the network program to be created without the network management tool being attached, which is useful for planning an automation system while a building is under construction.
Like a virtual wire, network variable bindings allow control information to be shared between function blocks or nodes.
Unicast bindings include one sender and one receiver, though they may be within the same function block.
Multicast bindings include fan-out and fan-in bindings, which are used to share the same control information among several function blocks.
The network variable configuration table includes the Selector IDs that are associated with a node’s network variables.
Alias network variables allow multicast bindings to avoid Selector ID conflicts.
LonWorks network domains include one or more subnets that include one or more nodes. The numerical identification of the domain, subnet, and node are used to precisely address message packets to individual nodes.
Each node includes an address table that specifies the destination address for the network variable updates it transmits onto the network.
Subnet broadcasts are isolated to a certain subnet by routers, but domain broadcasts are forwarded by routers to all nodes in the network domain.
Acknowledged message service requires a return response from the receiving node, confirming that a network variable update was received.
Unacknowledged message service is a one-way transaction where no response is expected from the receiving nodes.
Authenticated message service provides a high-security method of sending network variable data by requiring nodes to prove that they share the same authentication key.
The use of a network channel can be divided into time slots for nodes to transmit message packets onto the network. Assigning a priority time slot to a node guarantees that it can communicate reliably without packet collisions.
Configuration properties can be changed to customize node behavior and the control functions.
Plug-ins from node or network device manufacturers provide a user-friendly way to adjust configuration properties.
Heartbeat configuration properties define how often a network variable update is transmitted from a sending node.
With the configuration property SCPTmaxRcvTime, a receiving node can be set to lock out if a heartbeat is not received from a sending node within a certain period.
SCPTdebounce sets a delay period before a digital network variable is updated to avoid transmitting the pulses of a set of physical contacts that are changing state.
For commissioning, the Neuron ID of a LonWorks node or network device can be obtained by any of three methods.
The Wink command confirms that the tool can communicate with a node by causing the node to exhibit a physical response, such as flashing an LED.
Routers must be commissioned and on-line in order for the tool to communicate with nodes on their other side.