function xprime = FHN(t,x)
global R L C E 
xprime=zeros(2,1);
V_C=x(1);I_L=x(2);
%xprime(1)=-(F(E+V_C)+I_L+Iin(t))/C;
xprime(1)=-(F(E+V_C)+I_L-sqw(t))/C; % outward forcing direction
xprime(2)=(V_C-R*I_L)/L;