Who says that his design is never going to change and therefore we can code it into hardware, unless of course you incorporate some form of mechanism to allow to you update it in the field.
We are at the moment going through the hoops of getting a part of a design patented it really all down to how you word it as to how much protection it affords. In some respects it may be better not to apply for a patent as then you don't actually have to reveal how your idea works, in some areas just saying this is how the thing works is enough to allow people to design something similar which does the same thing.