First of all, thanks everybody.

Now I would like to ask something: how can you work in fixed point arithmetic? I mean, you don't know the values for the variables Ki, Kp and Kd. Calculating with fixed point must bring usual overflows, doesn't it? How many bytes do you use?

The key is that I'm trying to develop a generic controller. That's why I must be prepared to work with any values.

Thanks again.

Enrique