Error: Commands out of sync; you can't run this command now

[XX CVX]

CREATE DEFINER=`root`@`localhost` PROCEDURE `new_procedure`(in Cid int,out vv int)
BEGIN
set vv=Cid+1;
select * from test1;
END


res = mysql_real_query(&myCont, "call new_procedure(1,@tt)", strlen("call new_procedure(1,@tt)"));

res = mysql_query(&myCont, "SELECT @tt");


Error: Commands out of sync; you can't run this command now


How do I do get output @tt first;