Nuts and Volts - April 2017

Planning a National Instrument (NI) LabVIEW VI is different than planning other types of computer programs that are sequential in nature, such as assembly language and C.

Whereas a flow chart might work well when planning sequential programs, they probably won’t be of much help when planning a LabVIEW VI. So, what particular planning approach works well for LabVIEW VIs?

First, develop a written statement or description of what you want your program to accomplish, along with a title and a general program specification statement. Second, sketch out what you would like the front panel or user interface to look like. What basic controls, indicators, charts, etc., will be needed on the front panel to support the general program specifications? These controls and indicators can then be placed on the front panel at this point.

Each control or indicator that is placed on the front panel usually has an associated function icon that will appear on the block diagram as well. Some functions — like the MyRIO I/O functions on the block diagram — do not have icons that appear on the front panel. Following these suggestions will help you get your VI started and planned out. As far as the block diagram is concerned, when the icons are placed down with the front panel controls, they will not be in any useful placement, order, or have any connections between them. The block diagram format that the original NI Main VI (that was first opened in Part 1) uses will work very well for most VIs that you will develop (see Figure 3). The front panel is not shown since it will only contain the stop control on it. This format has a flat sequence structure with three frames placed down. The flat sequence will execute from left to right. The left or first sequence is commented as “Initialize.” The center frame has a while loop placed in it COM PUTE R CONTROL AND INTERFACING WITH THE NI MYRIO By David Ward

April 2017 23 Part 5: A temperature control system and data logger.

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The four previous articles have already demonstrated most of the features that this final project will bring together in a complete system. Refer to Photos 1 and 2 and Figures 1 and 2. There are a few new items in this VI (virtual instrument) that were not presented previously which will be explained in this final installment.