Ask HN: How Do You Handle Copyright and IP with Academic Professors?

Seeing this Question does not completely answer my doubts - (Ask HN: Programmers, how do you handle Copyright and IP in your contracts? [0] )

I am currently working under a professor who pays me for being a research assistant - he pays only 10 hours a week and does not cover the entire time spent on building the software.

How do I negotiate deal with my professor for this software, keep my IP options for future entrepreneurial options for myself ?

[0] https://news.ycombinator.com/item?id=9505269