Chapter 5
Accessing cFP-21xx Channels from PC Applications
©
National Instruments Corporation
5-3
cFP-21xx and cFP-BP-x User Manual
4.
The OPC server loads the last saved
.iak
file on startup. Select the I/O
items you configured in MAX that you want to read or write as a part
of this group.
Many OPC clients can use the Browse Address Space feature of the
FieldPoint OPC server to show you a list of all the I/O items you
configured in MAX. However, if the OPC client you are using does not
support this feature, you may need to type the item IDs of the I/O items
directly. The naming convention of the FieldPoint item IDs is
Comm
resource name\Device Name\I/O item name
, where the values
are the names given in MAX. For example, an item ID associated with
one of the I/O items might be the following:
FP Res\cFP-TC-120 @1\Channel 0
In most cases, the preceding steps are all that is required to configure an
OPC client to read from I/O items of the FieldPoint OPC server. In some
cases, the OPC client might require more information about the FieldPoint
OPC server. The following list contains additional information about the
FieldPoint OPC server, which you may find helpful.
•
The FieldPoint OPC server does not require an access path. Some OPC
clients expect the access path to be included in the item ID name or
might request the access path when you select I/O items. You should
be able to leave the access path blank (empty string).
•
The FieldPoint OPC interface is an out-of-process server.
•
The FieldPoint OPC server supports both synchronous and
asynchronous reads and writes.
•
The FieldPoint OPC server uses the GetErrorString method to return
error and diagnostic messages from the FieldPoint server and
hardware. OPC clients that do not support this method might give you
error messages like “Bad, non-specific” along with an error code.
Some OPC clients that do not support this GetErrorString method still
provide a way for you to manually look up the FieldPoint message
corresponding to the error code using the method.
Data Communications
The cFP-21
xx
network module provides several methods for
communicating and sharing data with other FieldPoint systems, computers,
and devices. The most common methods are to use DataSocket, serial VIs,
TCP VIs, UDP VIs, or Data Publishing VIs, as described in the following
sections.
