Hi Richard,
Could you be mores specific as to the problem that you're seeing? Do both of your calculations give the same value or are they different?
I opened up your code but I couldn't see the functions you were using since the subVIs were missing, are you able to upload them? I did, however, find the first subVI when I downloaded the very same VI from the online example. It looks like this VI will definitely give you a CRC-16-ANSI so I'm not sure what the issue could be. Are you certain that your polynomial is correct? It could be that you've got the right implementation but it's simply using the wrong polynomial.
I suspect that the first implementation is correct so long as the input data and polynomial are correct, so I'd also recommend probing the wires going into this VI to ensure that the numeric to string conversion happens as expected.
Best regards,
Jake A
Applications Engineer
National Instruments UK and Ireland