AMX NI-3101-SIG manual What is Dynamic Device Discovery?, Dynamic Device Discovery Concepts

NetLinx Security within the Web Server

What is Dynamic Device Discovery?

The Dynamic Device Detector (DDD) monitors the system for newly connected devices. New devices can be detected via either an external discovery protocol manager (built into firmware

build 320 or higher), Multicast reception of a Dynamic Device Beacon, or via the receipt of a beacon response on an application specified list of serial devices. This DDD process begins by detecting new devices within a NetLinx/Duet system, binding those devices to application instances, and then starting a Duet module to control those new devices.

Dynamic Device Discovery was created to take advantage of Java's Dynamic Class Loading and the Duet Standard NetLinx API (SNAPI). Java loads classes as they are needed. Therefore it is feasible to load a Duet control/protocol module on the fly as each new device is discovered. SNAPI provides a fixed interface for communicating with a certain type of device. The "glue code" refers to the developer defined NetLinx program that runs on a Master and controls a system.

Take for example a VCR. The majority of control features are common to all VCRs (play, stop, pause, etc.). SNAPI provides the "glue code" developer the ability to write common code that will control any type of VCR having an associated Duet module. The underlying Duet module could be swapped in and out based on the actual physical device with no changes needed to the higher level "glue code".

Dynamic Device Discovery Concepts

Feature	Description
Application Device:	• A Duet Device (41000-42000) that is used as a control interface
	to a physical device. This is also referred to as the Duet virtual
	device.
	• All control requests are made to the application device rather
	than to the physical device.
Binding:	• In concrete programming, the application device is forever
	associated with the NetLinx physical device. In DDD, this
	association is dynamic.
	• The act of associating an application device with a physical
	device is called “binding".
Device Discovery:	• In DDD, physical devices are detected in the system at
	run-time.
	• There are two different methods of detection: via Dynamic
	Device Discovery Protocol (DDDP) or via user definition within
	the Master’s Web interface (page 108).
SDK Class:	• Each application device in the DDD world is associated with a
	particular device type as defined by SNAPI.
	• When using a VCR or a Receiver as an example, each of these
	device types would correspond with a Java Interface within the
	Duet Device Software Development Kit (SDK).
	• When writing programs for DDD, the developer specifies the
	device type of a particular application device by using one of
	these SDK Class names.
Polling:	• Dynamic physical devices can be detected by DDDP through
	both Serial and IP interfaces.
	• While IP connections are then able to utilize the network’s
	higher layers of multicast to broadcast their existence, Serial
	devices speak a fixed protocol that is incompatible with DDDP.
	• Serial devices are passive and will only broadcast their
	existence if polled to do so. The program developer must
	specify which NetLinx interfaces/ports (i.e. serial ports) should
	be polled for devices.

NI-3101-SIG Signature Series NetLinx Integrated Controller 101