Programming Analog Input with LabVIEW

Programming Examples

The LabVIEW ELVIS III Toolkit provides examples of using analog input channels to perform signal acquisition. You can find these examples in the labview\examples\ELVIS III\Real-Time Control Applications\Analog IO\Analog IO.lvproj directory.

LabVIEW RT Express VIs

Use the Express VIs to interactively configure the settings for the I/O channels. When you place an Express VI on the block diagram or double-click an Express VI, a configuration dialog box appears. Use this configuration dialog box to configure the Express VI. Find the Express VIs on the Academic I/O » Control I/O subpalette on the Functions palette, as shown in the following figure:

The LabVIEW ELVIS III Toolkit provides Analog Input Express VI to access the Analog Input channels.

LabVIEW RT Low Level VIs

Use the Low Level VIs to have more programmatic access to settings of I/O channels. For example, you can use the Low Level VIs to open or close certain channels and change the channel configuration at run time. Find the Low Level VIs on the Low Level palette, as shown in the following figure:

The LabVIEW ELVIS III Toolkit provides the following Low Level VIs to access the Analog Input channels:

• Analog Input 1 Sample VIs
• Analog Input N Samples VIs
• Analog Input Continuous VIs

Select Help » Show Context Help or press <Ctrl-H> to display the Context Help window, from where you learn the basic information about each of the Express VIs and Low Level VIs. To learn more details about the VIs, refer to the LabVIEW ELVIS III Toolkit Help by clicking Detailed help at the bottom of the Context Help window, shown as follows:

LabVIEW FPGA I/O Nodes

Use the FPGA I/O nodes from the FPGA palette to access the Analog Input channels on the NI ELVIS III. You can also use the FPGA I/O property nodes if needed. Channels from both banks on the NI ELVIS III can be used in a single FPGA I/O node. The I/O banks are denoted as connectors in the software. The following figure shows a VI that uses FPGA I/O nodes to read inputs from AI channels 0 to 1 on Bank A and Bank B.

The FPGA palette does not provide any devoted FPGA I/O nodes for specific protocols such as PWM and Encoder. To access these protocols, use the LabVIEW RT VIs instead.

Refer to the FPGA I/O Functions section of the LabVIEW FPGA Module Help for detailed information about using the FPGA I/O nodes to perform operations on FPGA targets. Refer to the NI ELVIS III section in the NI Compact RIO Device Drivers Help to learn what terminals and I/O methods and properties you can access for the NI ELVIS III. You can access these help files by selecting Help » LabVIEW Help in LabVIEW, or search for their online versions on ni.com/manuals.