Domestic mains electricty at 400 Hz? Really? Where about would that be??
Well, you got me on that one. It seems my memory has misled me. 400Hz is used in certain systems, but not as a municipal/utility power grid due to efficiency issues. So with 400Hz support, this project can be used in certain aerospace applications. 
It's just as well. The performance of the code at 400Hz wasn't very good, and now I don't have to be annoyed about it.
Ryan, I am concerned about the performance of the code with other things going on too - and it will suffer if much more than a few very simple tasks are being done. I hadn't thought of a good way to handle that as of last night. But since you mentioned the software interrupt, I'm rolling that around in my head now. We'll see what I can come up with over the weekend. I should know better than to say "NEW CODE IS FINISHED!!" Is software every really finished? 