Fix invalid comparison between signed char and unsigned char
Fix invalid comparison between signed char and unsigned char

GomSpace/libcsp,satlab/libcsp,Psykar/kubos,pacheco017/libcsp,kubostech/KubOS,Psykar/kubos,Psykar/kubos,Psykar/kubos,satlab/libcsp,pacheco017/libcsp,pacheco017/libcsp,libcsp/libcsp,Psykar/kubos,pacheco017/libcsp,kubostech/KubOS,libcsp/libcsp,Psykar/kubos,GomSpace/libcsp,satlab/libcsp,Psykar/kubos,GomSpace/libcsp