Function nros_platform_timer_create_periodic 

pub unsafe extern "C" fn nros_platform_timer_create_periodic(
    period_us: u32,
    callback: nros_platform_timer_callback_t,
    user_data: *mut c_void,
) -> *mut c_void

Register a periodic timer that invokes callback(user_data) every period_us microseconds. Returns the platform-native handle on success, NULL on failure.