For the past couple weeks I have been mostly refining small bugs, which were originally rendering the RTOS usless, as well as refactoring the code for simplicity rather than elegancy.

1. Transition to Actual Hardware

Renode is great for simulation, but it ended up hiding a bunch of race conditions in the population methods and the main scheduler that led to no code actually running during the IRQ handler calls. I spent a lot of time securing those resources and finally got the scheduler mostly finished up. Also, I decided to just take out the double preempts entirely since they were adding way too much complexity for absolutely zero speed benefits in practice (plus they were creating detrimental but rare race conditions).

2. Code Refactor

To make things run a bit more consistent, I restructured how the control loops operate. I ended up merging the dShotGeneration task with the parent IMU control loop, so now everything from reading the sensors to pushing motor commands happens in one clean sequence (rather than including an unnecessary preempt). I also built out a brand new CRSF control loop to handle all the radio parsing and state machine updates in its own dedicated space (just for consistency). Lastly, while doing a final pass on the code, I realized that in my dShotGeneration helper, I had forgot to scale the values by a factor of 1/2000, as the inputs require the value to be between 0 and 1 (not 0 and 2000).

3. Final DMA Iteration

The biggest relief was finally getting rid of the old blocking USART system. I finally transitioned away from manually handling the streaming by polling flags in a loop, which was tying up the processor way more than it should have. Everything has been converted over to a blocking DMA system, so the hardware can just handle all the memory transfers in the background while the CPU focuses on actually keeping the drone in the air. Overall, I think that this will be the final iteration of the RTOS DMA pipeline, as now that it is solid and works with all the edge cases, theres no need to change it.

4. Timeline

With almost all the major bugs fixed, I am going to ship the project! While it is not 100% done, it will likely be as close as it will get during the timeframe of the Stardance hackathon, and with it so close, theres no reason not to ship. Anyway, I will keep the source as the main project rather than a release, so if I do end up fixing any major bugs, they will get patched either before or during project review (besides most of these bugs are only detectable on actual hardware).

I will most likely finish the RTOS in the next couple weeks (by the end of October), and will finish the drivers for the ESC and RM by latest end of November (for more timing refer to the README).

Thanks to everyone who supported me throughout this project (hopefully me and my friend can get this drone flying in another Hack Club Hackathon!).