I started looking at this last night [1] since there's an open SDK available (called SDK3) [2] but it seems like keil is involved in compiling it and I'm out of my depth when it comes to embedded stuff at the moment

1. https://notes.tahnok.ca/blog/Smart+Ring+Reversing/2024-10-13... 2. https://gitee.com/BXMicro/SDK3