Setting the Size of Array Controls in LabVIEW FPGA

Updated May 11, 2023

Reported In


  • LabVIEW FPGA Module

Issue Details

I have an array control or indicator on the front panel of my FPGA VI, and LabVIEW FPGA requires array controls to be a fixed predetermined size, or resolvable to a fixed size by the compiler. How can I set the size so that I can compile my VI?


In your FPGA VI, create an array Control, Constant, or Indicator.

Right-click on the Index Display or the border of the array, and choose Set Size... The following dialog box will appear:

There are two options:

  1. Variable: This is the default behavior. The user can add and remove elements at will.
  2. Fixed: The array will always be the same length, preventing the user from adding or deleting array elements at any time.

For array indicators, the same options are available, and a checkbox above selects between using the default Adapt to Source Wire behavior or one of the behaviors listed above.

Additional Information

Arrays are always defined in terms of specified dimensions in FPGA, because it requires pre-allocated arrays and does not support dynamic memory allocation. FPGA VIs only support one-dimensional arrays that resolved to a fixed-size at compile time. To make this more transparent, you can restrict the size of arrays for FPGA targets.