# Using desolve_odeint with external stimulus

I'm trying to numerically solve a two-variable system of differential equations with a periodic external driver (square wave). Right now, the code I have is:

```
from scipy.signal import square
def sqstim(t, amp=1):
return (amp/2)*float(square(t))+amp/2
var("V,w")
trange=srange(0,100,0.1)
def eqns(t):
return [1/100*(-w+(V^3-V)+sqstim(t)), V-0.2*w]
sol=desolve_odeint(eqns, times=trange, ics=[0.1,0.1], dvars=[V,w])
```

This gives `"TypeError: 'function' object is not iterable"`

. What should I do instead?