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Use the filtering VIs on the FPGA Math and Analysis palette to filter FPGA I/O. By default, the FPGA filtering VIs accept a single input channel. However, you can use the Number of channels option on the configuration dialog box of the filtering VI to configure the VI for multiple input channels.

Using the FPGA Filtering VIs with Multiple Input Channels

When you configure an FPGA filtering VI for multiple input channels, you must send each input channel to the filter VI in succession. You can bundle the input channels into an array and use a For Loop to ensure that the filter VI receives each input channel in succession, as shown in the following figure.

In the previous figure, four analog input signals pass through a Butterworth Filter and a Notch Filter. To maximize throughput, the VI uses Feedback Nodes to create a pipeline.

Note  Some FPGA targets support the I/O Sample method, which provides data from multiple input channels in succession. If you use the I/O Sample Method, you do not need to bundle input channels into an array. Instead, include the FPGA I/O Method Node configured with the I/O Sample method inside the For Loop. Refer to the specific FPGA target hardware documentation for information about support for the I/O Sample method.

Configuring Filter Coefficients

You can design the host VI to dynamically configure the coefficients of the FPGA filtering VIs at run time. On the configuration dialog box of the filtering VI, select Show configuration terminal to display an input terminal on the filtering VI that specifies filter coefficients. If you configure the filtering VI for a single channel, the configuration terminal is a fixed-size array of integers called scaled coefficients. If you configure the filtering VI for multiple channels, the configuration terminal is a cluster called configuration. The cluster includes the scaled coefficients array and a channel index integer that specifies the channel to which the coefficients apply. You can alter filter coefficients for only one channel at a time. The filtering VI continues to use either the default coefficients or the last coefficients you specified for the channel until you specify new coefficients.