Notes to CDIF's open zwave implementation
This module relies on openzwave-shared, please refer to its prerequisites on how to install it on the system.
The concept of Z-Wave's command class and values are similar to other open standards which categorized them into "services", "characteristics" or "state variables". So in this module's design we decide to map them accordingly. E.g. the concept of command class would be equal to service, and value equal to state variable which is managed by the service. We use this to create the device model for Z-Wave based devices. After connected to the Z-Wave network, this module would listen to the Z-Wave library events and selectively emit device event to CDIF.
Because of Z-Wave's low power design, commands are not guaranteed to always successfully deliver to device, for example battery powered devices may stay in sleep state for a long time and won't respond to any action or query command. In addition, in Z-Wave there is no guarantee of something similar to the "service discovery" process in other protocols, where controller can issue commands to fully explore a device's capabilities at one time. For battery powered devices, it could take hours to report its full capabilities. Due to these facts, this implementation would progressively build CDIF's common device model whenever a new value or node info is reported through 'value add', or 'node ready' event. This means a discovered Z-Wave device through CDIF's REST interface may automatically refresh its device model from time to time.
Since there is no reliable way to query a Z-Wave device for its latest status, this implementation would return CDIF's cached status value to the client upon a read action call. Because the underlying zwave.setValue() library call doesn't return error, value write action calls would assume always success and update CDIF's cached value status, which could also be updated by 'value change' event.
Due to device availability, for now this module is only tested with below products:
Limitations
At this time below Z-Wave features are not supported:
- Association group and scene control (maybe these features could be fulfilled by the rules engine built on top of CDIF)
- Z-Wave global operations such as device polling, network healing, controller reset etc. (maybe they could be wrapped as controller's service)
- Security API
See following links for more details: