Looking for Cannedy of Londonderry Ireland

Hello all,
I have been searching for 10 years now for more information on my GGGGrandfather John Cannedy/Kennedy born @1740 in Londonderry Ireland and died @1820 in Tennessee , he married Ann ????? born @1750 in Scotland and died also 1820 in Tennessee. They had children: James, John C., Martha and Sarah.. John Cannedy has been a brick wall for me now and somedays I get so frusrated I go for walks to clear my mind before I come back to him. Any help would be deepley appreciated. I need all the help I can get...
thanks so much
Jean Linhart