Hi again, just another small note...

Bill Couture wrote :

> Since the PID is in the interrupt, it runs EXACTLY on
> schedule.  Although,
> there is some jitter, based on the values in the loop.  For
> example, with
> PID, Kp, and delta_position all long ints
>    PID += Kp * delta_position;
> is *MUCH* slower (about a factor of 2) if delta_position is negative
> intead of positive. In fact, if you do it right, you can save
> processing
> time with statements like
>    pos_delta_pos = (current - desired);
>    neg_delta_pos = (desired - current);
>    if (current > desired)
>       PID += Kp * pos_delta_pos;
>    else
>       PID -= Kp * neg_delta_pos;
> (you do have to be careful that you don't spend more time saving time,
> but if you're careful you can save considerable time.)

This app is written in C, right ?
Maybe you could speed up the PID calculation by
re-writing it in optimized ASM and calling that from
your C code ?

Jan-Erik.

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