I agree with the state machine idea. Attached is an example for you. Please read the notes I have included and play with it a bit to make sure it does what you want it to, then modify for your code.
The way this works, as the while loop spins, the case statement is evaluated every time with a value passed in from the previous iteration of the loop. This allows you to evaluate the "state" of the program and decide what code you want to execute in the next iteration of the loop. In other words, every time you go through the while loop, the case thats run decides which case will run next time.
In the first time I seed the shift register for the case statement with 0. This is the initial case. The condition for going from state 0 to state 1 is that all inputs are high. After this, in state 1, if any input goes low, you are placed into state 2, the reset state. The only way out of this state is to hit the reset button... and so on. Note that you have a choice on where the loop goes after a reset... do you want it to immediately fail if all inputs are not high, or do you want it to start like it did, waiting first for all inputs to go high. This will decide where you want the reset state to send you, either to state 0 or state 1. See the notes on the diagram for further info.
One word of caution to those reading this interested in the state machine idea... if you use it... KEEP IT SIMPLE. This type of code can be very frustrating to debug. If your app will use complex reasoning to decide which state to go to, or you think there would be many many states, try to think of a way to simplify. If you dont, you will be stuck trying to figure out which state it is in and why for hours sometimes, before you can even start on the problem. Strip it down to what you need for a state decision as much as absolutely possible. Trust me on this one... I have been there.
Attached VI saved in LV 8.0 format.
Good luck,
Message Edited by cybertazer on
04-04-2008 08:50 AM
CyberTazer
Software Systems Engineer
to help.
