Here's something interesting I found in the LabVIEW Help documentation:
Quote:
Input/Output
Input/Output (I/O) calls generally incur a large amount of overhead. They often take much more time than a computational operation. For example, a simple serial port read operation might have an associated overhead of several milliseconds. This overhead occurs in any application that uses serial ports because an I/O call involves transferring information through several layers of an operating system.
The best way to address too much overhead is to minimize the number of I/O calls you make. Performance improves if you can structure the VI so that you transfer a large amount of data with each call, instead of making multiple I/O calls that transfer smaller amounts of data.
For example, if you are creating a data acquisition (NI-DAQ) VI, you have two options for reading data. You can use a single-point data transfer function such as the AI Sample Channel VI, or you can use a multipoint data transfer function such as the AI Acquire Waveform VI. If you must acquire 100 points, use the AI Sample Channel VI in a loop with a Wait function to establish the timing. You also can use the AI Acquire Waveform VI with an input indicating you want 100 points.
You can produce much higher and more accurate data sampling rates by using the AI Acquire Waveform VI, because it uses hardware timers to manage the data sampling. In addition, overhead for the AI Acquire Waveform VI is roughly the same as the overhead for a single call to the AI Sample Channel VI, even though it is transferring much more data.
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This may be why the communication is so slow. If we could have higher-level commands integrated into the CAN driver, then we could achieve greater communication speeds.
I think an excellent addition would be the ability to get the same status from multiple controllers, or set the same configuration/output of multiple controllers (with different data for each one).
Unfortunately, this is beyond my current ability; I don't know how to make .out files for the cRIO, and I'm certainly not interested in programming the Jaguars in C.