If you are looking for the official firmware, avoid third-party "driver update" sites. These often contain malware or outdated files. Follow these steps to find the legitimate link: 1. Manufacturer Support Portals
If you cannot locate a live link after exhaustive searching, consider replacing the NM368818 controller entirely – modern drop-in replacements (like the MKS DLC32 or FluidNC) offer open-source firmware and active support. nm368818 firmware link
Once I have a better understanding of your requirements, I'll do my best to assist you in writing the feature. If you are looking for the official firmware,