Chapter 4
Installing and Using the FieldPoint Software
4-16
ni.com
Using the FieldPoint LabVIEW VIs
When you install the FieldPoint software, a library of FieldPoint VIs is
created if LabVIEW has already been installed on your computer. The
FieldPoint VIs (FP Open, FP Get Configuration Info, FP Create Tag,
FP Advise, FP Read, FP Write, and FP Close) directly access the I/O Items
you configured in the FieldPoint Explorer program. In addition, a set of
examples is placed in your
LabVIEW Examples
directory. These examples
are the best way to get familiar with the LabVIEW VIs. The
FieldPoint
LabVIEW Help
document is in the same program group on your Windows
taskbar as the FieldPoint Explorer program. This help document explains
how to use the FieldPoint VIs.
A simple FieldPoint application to read an I/O Item might only need to use
four of the VIs. To create an example of such an application, complete the
following steps and refer to Figures 4-8 and 4-9. This application reads the
inputs from the I/O Item named
All
shown in Figure 4-1.
1.
Use FP Open to open the server. By default, the server opens with the
configuration file you last saved with FieldPoint Explorer.
2.
Use FP Create Tag to create a handle to an I/O Item that you defined in
FieldPoint Explorer. You provide three string names to this VI to
indicate which I/O Item you want access to. These three strings are the
names given to the communications resource, the device, and the I/O
item. Figure 4-7 shows default names as they might appear when you
use the
Find Devices
button in FieldPoint Explorer.
3.
Use FP Advise to continuously monitor the I/O Item at the rate
specified in FieldPoint Explorer. (You can also set a new rate with this
VI.) In this example, the while loop executes at this advise rate. If you
used FP Read VI here instead of FP Advise, the loop would
free-run
at
the fastest rate it could sustain, reading the I/O Item over the serial port
each time the loop ran.
Note
Do not put more than one FP Advise VI in a loop. All VIs in a loop execute only
once each time a loop runs, and FP Advise VIs only complete at their advise rate. If you
had more than one FP Advise VI in the loop, the loop (and therefore all of the FP Advise
VIs in the loop) would only execute at the slowest rate of the Advises. The loop might not
execute at all if any of the Advises is set to complete “On Data Change,” and the data of
the corresponding I/O Item never changed.
