Zephyr: State Machine Framework Refactor Lab

BME554L - Fall 2025 - Palmeri

Git Version Control

• Use best practices for version control (branching, commit messages, etc.).
• Do all development on a dedicated branch that is merged into main once it is functional.
• Commits should be very specific to the changes/additions you are making to your code. This will help you and others understand what you did and why you did it.
  
• On a given development branch, try to implement one small piece of functionality at a time, commit it, and then move on to the next piece of functionality.

Important

You do not want one, monolithic git commit right before you submit your project.

Refactor: State Machine Framework

1. Create a new development branch in your forked repository you have used the last few weeks called refactor_smf.
2. Refactor your code to use the Zephyr State Machine Framework (SMF).
   • Use entry and exit substates to handle state transitions where something should be done “once” when entering or exiting a state.
   • Refactor code to make sure that state-specific things are done in that state. For example, if an error LED should only be on in the ERROR state, then the code to turn on the LED should be in the ERROR entry state and not done in the exit of the previous state.
   • Make sure that your device initialization is done in an INIT state (so that, in the future, a soft reset can allow the device to be completely re-initialized).
3. Make sure that your state diagram is updated to reflect these entry / exit actions. This diagram should exactly match your firmware implementation of the SMF.
4. Qualitatively make sure that your device continues to function as expected.

How do I ask for help?

1. If you have a general / non-coding question, you should ask your TAs / Dr. Palmeri on Ed to allow any of them to respond in a timely manner.
2. Push you code to your GitLab repository, ideally with your active development on a non-main branch.
3. Create an Issue in your repository.
   • Add as much detail as possible as to your problem, and add links to specific lines / section of code when possible.
   • Assign the label “Bug” or “Question”, as appropriate.
   • Be sure to specify what branch you are working on.
   • Assign the Issue to one of the TAs.
   • If your TA cannot solve your Issue, they can escalate the Issue to Dr. Palmeri.
4. You will get a response to your Issue, and maybe a new branch of code will be pushed to help you with some example syntax that you can use git diff to visualize.

What to Submit

1. As with the previous labs, push this development branch to Gitlab and merge it into main.
2. Create an annotated tag for that merged commit called v1.4.0.
3. Create an Issue assigned to Dr. Palmeri to review your code for v1.4.0. (Teaching team will upload a zip archive of your project to Gradescope.)