See RTIC (real time interrupt-driven concurrency) formerly known as RTFM (real time for the masses - renamed due to confusion with a similar acronym about reading manuals).
If your c++ code uses the c ABI (application binary interface) then you can call it easily too. There is a tool called rust-bindgen which will automatically generate the required rust code from header files.
https://rtic.rs
This library gets a lot of attention in the embedded rust community and is designed for tiny devices like an arm M0 mcu.