I’d bet that the problem relates to this being a C-compiled library and you using a C++ source file.
Try surrounding your include statement with:
__BEGIN_DECLS
#include “sdk/Maestro/protocol.h”
__END_DECLS
…which is the equivalent of doing:
#ifdef __cplusplus
extern “C” {
#endif
#include “sdk/Maestro/protocol.h”
#ifdef __cplusplus
} /* extern “C” */
#endif
…which in turn will advise the compiler to use a C naming convention for the methods in the library. Should fix the linking problems.