How to know if my code is patentable

if you want to protect your intellectual property then a patent is not practically that protective. It is costly and you need to apply in each country I believe.

Best is to physically protect it yourself e.g. through encrypted netlist.

For a patent you need to make claim of what is new part of the design and legal wording could be hard and you may need to pay agencies for that.

It must also not be any algorithm/implementation known in public domain or anything that is too obvious to be regarded as new.

Just some thoughts.

Alternatively approach a manufacturer without a patent giving then vague description and hoping they might just buy it from you or share royalty. This hard way. Dyson approached vacuum cleaner companies in the 80s (I think) and they rejected his ideas then regretted not buying them off to kill them.