[Greg McKaskle]

There were a number of questions raised. I'll respond to the ones I remember.

What is atan2 of 0 and 0. In LabVIEW, it is 0, at least on an Intel mac. I don't have a cRIO in front of me. I hope/suspect that the PPC LV will return the same, but since I don't have the LV test suite in front of me to prove that is a tested result, I'll speculate that it returns zero. The applied mathematicians on the LV team tend to be picky about things like that, so they have test suites that enforce the results across platforms. Can someone test for sure?

What does the FPGA do? Is it Intel? It is not Intel, and it doesn't natively do FPU operations. It is a field programmable gate array, a bunch of low level logic operations. In order for it to do an integer addition, an adder has to be constructed in it. If you also wish to multiply, a multiplier has to be constructed. The results of those operations are determined by the adder or multiplier you emit to the FPGA. The FPGA image used for FRC contains no floating point trig operations, and in fact I doubt it contains any floating point operations at all as they consume gates very quickly.

Which is faster/better, the atan2 operation, or a lookup table? I have my suspicion/opinion, but this is the sort of thing where the actual answer is ... it depends. Rather than take someone's answer, the approach I'd encourage you to take is to implement both and learn the magnitude of the operations involved. If the lookup table is pretty fast, what if you interpolate for more precision. My point is that knowing A is faster than B is useful info, but more useful is to know the rest of the tradeoffs, and to know how much faster and why.

Greg McKaskle