This is an excellent illustration of one of the (mostly-ignored) Golden Rules of Software Development -- "Write the Documentation First".
Don't worry about how you will control or sequence all of the devices that you have. Instead, concentrate on what you want to do. Here are some sections your Document should cover:
- Describe the various sensors, along with a description of what they are measuring and at what data rate you need to interrogate each of them (they might not all be the same)
- Describe what communication protocol your sensors use (VISA/Serial, TCP/IP, USB, etc.).
- Describe the general operation of the system when it is running, concentrating on how the various sensors and controls interact with each other.
- Describe the minimum set of Controls you need on your Front Panel. It might come down to two: Start, and Stop.
- Describe the outputs you need in general terms. Again, don't concentrate on how to get the data, just on what you need to see.
Once you have the general layout of "what" you want to do, you may see that it follows a natural (single) sequence -- Initialize/setup, Start, Run/Display, Shut Down. This suggests a single sequence, possibly best realized by having one VI do each of these four tasks, sequenced by using the Error Line and "parameter wires".
If you need to start, stop, and restart, a State-Machine-like implementation, such as the Queued Message Handler (from NI) or the JKI State Machine, might be more appropriate. Knowing in advance "what" you want each State to do will be very helpful in creating your code. Note that there are "examples" of the Queued Message Handler -- start LabVIEW, go to New Project, and choose Queued Message Handler to build one.
Bob Schor
