Step 1. open objects, Step 2. start communication, Step 3. run your devicenet application – National Instruments NI-DNET User Manual

Page 27

Chapter 3

Developing Your Application

NI-DNET User Manual

3-8

ni.com

Step 1. Open Objects

Before you use an NI-DNET object in your application, you must configure
and open it using either

ncOpenDnetIntf

ncOpenDnetExplMsg

, or

ncOpenDnetIO

. These open functions return a handle for use in all

subsequent NI-DNET calls for that object.

The

ncOpenDnetIntf

function configures and opens an Interface Object.

Your NI-DNET application uses this Interface Object to start and stop
communication. The Interface Object must be the first NI-DNET object
opened by your application.

The

ncOpenDnetExplMsg

function configures and opens an Explicit

Messaging Object, and the

ncOpenDnetIO

function configures and opens

an I/O Object.

Step 2. Start Communication

Start communication to initialize DeviceNet connections to remote
devices. Use the Interface Object to call the

ncOperateDnetIntf

function with the

Opcode

parameter set to

Start

The following optional steps can be done before you start communication:

•

For an I/O Object, if it is not acceptable to send output data of all zeros,
call

ncWriteDnetIO

to provide valid output values for the initial

transmission.

•

For an I/O Object, if your application is multitasking, call the

ncCreateNotification

ncCreateOccurrence

function with

the

DesiredState

parameter set to

Read Available

. This notifies

your application when new input data is received from the remote
device.

•

For any NI-DNET object, if any of the Driver attributes needs to be
changed, call

ncSetDriverAttr

with the attribute Id and attribute

value. The

ncSetDriverAttr

function cannot be called after the

communication has started.

Step 3. Run Your DeviceNet Application

After you open your NI-DNET objects and start communication, you are
ready to interact with the DeviceNet network.

Complete the following steps with an I/O Object:

Call the

ncWriteDnetIO

function to write output data for subsequent

transmission on the DeviceNet network.