Houdini connection with Arduino

[stacey]

Hello, everyone! I want to change the height of the tube by collecting the data from arduino. I refer to this tutorial, but it seems that I still have some problem with it. The screenshot are posted below. Can anyone help me with it? 

The error message shows like this ：

Error:       Unable to evaluate expression (
Traceback (most recent call last):
  File "<stdin>", line 2, in expression
  File "opdef:/Object/gwPlatform?PythonModule", line 18, in getHeight
  File "opdef:/Object/gwPlatform?PythonModule", line 8, in updateValues
AttributeError: 'module' object has no attribute 'ser'
 (/obj/gwPlatform1/tube1/tube1/height)).