//   This is a component for LinuxCNC HAL
//   Copyright 2006 Jeff Epler <jepler@unpythonic.net>
//
//   This program is free software; you can redistribute it and/or modify
//   it under the terms of the GNU General Public License as published by
//   the Free Software Foundation; either version 2 of the License, or
//   (at your option) any later version.
//
//   This program is distributed in the hope that it will be useful,
//   but WITHOUT ANY WARRANTY; without even the implied warranty of
//   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//   GNU General Public License for more details.
//
//   You should have received a copy of the GNU General Public License
//   along with this program; if not, write to the Free Software
//   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
component ddt "Compute the derivative of the input function";
author "Jeff Epler";

description """
For every function call from the real time thread, calculate the
difference between the old and current input value divided by the
timer elapsed since the last call.
""";

notes """

As this only work on two consecutive input values, it will only work
well if the input change every function call, and not work so well if
the rate of change is very low and the input change do not happen
every time the real time function is called.

""";


pin in float in;
pin out float out;

variable double old;

function _;
license "GPL";
;;
double tmp = in;
out = (tmp - old) / (period * 1e-9);
old = tmp;