I have tried researching this and can't seem to find something that exactly matches what I am trying to do...
In a nutshell, this is what I am trying to do: I have a (non-ni) relay control board with which I communicate via tcp over ethernet. The manufacturer provides a .net dll for use in various programming languages, which I am successfully using in labview. The relay board has 32 relays, divided into 4 "banks" of 8 relays, each addressed with a command like (this is just pseudocode) relay_on(bank, relay) and relay_off(bank,relay). No problems there. For all 32 relays I had to create front panel indicators giving the relay state (on or off) and controls that either set or reset the relay in "manual" mode or apply pwm with user-set on and off times in "auto" mode. I basically setup the vi based on a fsm i devised. There is a button that switches between manual and auto. Still no problems there.
Sorry for the long-windedness but I'm trying to build up to the issue I'm having, and unfortunately I am not in a position to be able to post a vi.
Here is the issue: the method I am using to automatically turn the relays on or off based on on/off times is this: if the relay is set to "on" in auto mode, an interation in a dual for loop (8 inside of 4) that parses 2d arrays of on times and off times compares an initial ms tick value to the current ms tick value and sees if the on or off time (based on current relay state) is exceeded, switches the state, and, on a high-to-low transition, increments the appropriate element in a 2d count array.
I'm not sure if I'm painting a good picture but the bottom line is this: I have some serious timing problems. When only 1 relay timer is turned on, the timing is fine. But when I have the timers turned on for all 32 channels, everything goes haywire. Some relays follow the on/off times "relatively" closely to with 1 second (not that great) and others that have a period of, say, an hour, switch in something like 5 seconds.
Again, I'm sorry I can't post code, but I think this is a (somewhat) simple matter of determinism and independent timed loops. IS there a better way to "poll" all 32 relay channels, check for elapsed on or off time, and switch states when this time exceeds a user-defined timer value? I'm using seemingly countless 2d arrays to handle all the different per-relay indicators and controls (4 rows for bank, 8 columns for relay #) that are difficult enough to parse, but then sequentially checking whether the user turned the timer on or off, checking the on or off time elapsed, writing a new state, reading the state back to verify the relay actually switched, updating a counter AND updating the appropriate front panel indicators AND writing the counter array to a log file to boot... sufficed to say my block diagram is a birds nest. I avoided sub-vi's because frankly I figured zillions of sub-vi's would simply bog down the computer memory and processor even more. Also, as far as I can tell I can only send one write or one read at a time, since the board only has one ip address/tcp port. I tried loading multiple instances of the dll but they run into each other and throw exceptions because the port is busy.
Let me restate/rephrase the question: what's a good way to handle all these operations, minimize loop time, and improve timer accuracy? I've read about the "producer/consumer" methodology, but not only am I not very clear on how that works since I've never used those queue/notifier/semaphore, etc. vi's, adding all those loops would seem only to turn a big bird's nest into a gigantic bird's nest.
Help!
