Is it okay to tell your manager that I am not making progress on an?
I can answer this question. A Lot of the times, the difficulty in making progress comes from the unknowns of the projects when developing an embedded system. Make sure you understand the requirements properly. If the requirements are not clear, then ask the concerned person/team about what is not clear. Ask Questions. Dont be afraid. Its ok to ask than to be sorry about it. The Legacy C code might be written in a way, that nobody other than the original developer might understand. There might be some magical code that will have no documentation whatsoever. Lot of the code might depend on some protocols or standards or specifications. But you might not have access to the document. Ask for it. Reach out to the communities. Lot of the time, the Hardware/Software you are working on might have bugs or not documented properly. So the issue might not be from your side. Post your question on Stack Overflow with the right set of tags. Understanding how the system works might help you. Go step by step. Learn to use a debugger. Learn to use a logic analyzer. Learn how the software stack/SDK, compiler toolchain and hardware is put together. Finally, Inform the tech lead or manager about the issues that you are facing. Ask for their help. Experience matters. They should help you out. If not, the problem is on their table to resolve.