Ahem... people!!!!

The compiler is telling you what the problem is... let's all go back and read the MANUAL as to the correct SYNTAX for SERIN...

Not this...

Serin s_in, T9600, 1000, no_data, ("x"), [d0]

...but this...

Serin s_in, T9600, 1000, no_data, ["x"], d0

There's even an example in the book - read it!