Dynamic Device Discovery Protocol (Dddp); Dynamic Device Discovery Concepts - AMX VISUALARCHITECT 1.1 Manual

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Adding Devices to the System

Dynamic Device Discovery Protocol (DDDP)

NetLinx Masters equipped with firmware build 320 or higher support Dynamic Device Discovery, via

the Dynamic Device Detector (DDD).

The Dynamic Device Detector (DDD) monitors the system for newly connected devices. New devices

can be detected via either an external discovery protocol manager, 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 inter-

face.

• SDK Class:

Each application device in the DDD world is associated with a particu-

lar 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. But whereas IP connections are then able to

utilize the network's higher layers of multicast to broadcast their exist-

ence, Serial devices speak a fixed protocol that is incompatible with

DDDP. Serial devices are passive and will only broadcast their exist-

ence if polled to do so. The program developer must specify which

NetLinx interfaces/ports (i.e. serial ports) should be polled for devices.

VisualArchitect v1.1

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Troubleshooting

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Dynamic Device Discovery Protocol (Dddp); Dynamic Device Discovery Concepts - AMX VISUALARCHITECT 1.1 Manual