//   This is a component for EMC2 HAL
//   Copyright 2006 John Kasunich <jmkasunich@users.sourceforge.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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

component oneshot "one-shot pulse generator";

description """creates a variable-length output pulse when the input changes 
state. This function needs to run in a thread which supports floating point
(typically the servo thread). This means that the pulse length has to be a
multiple of that thread period, typically 1mS. 
For a similar function that can run in the base thread, and which offers higher 
resolution, see "edge".""";

pin in bit in "Trigger input";
pin out bit out "Active high pulse";
pin out bit out_not "Active low pulse";
pin in float width=0 "Pulse width in seconds";
pin out float time_left "Time left in current output pulse";

param rw bit retriggerable=TRUE "Allow additional edges to extend pulse";
param rw bit rising=TRUE "Trigger on rising edge";
param rw bit falling=FALSE "Trigger on falling edge";

option data internal;
option extra_setup yes;

function _ "Produce output pulses from input edges";
license "GPL";
;;

typedef struct {
    double timer;
    char old_in;
} internal;

EXTRA_SETUP(){
    data.timer = 0.0;
    data.old_in = 0;
    return 0;
}

FUNCTION(_){ 
    int new, old, trigger;

    new = in;
    old = data.old_in;
    trigger = 0;
    /* detect edges */
    if ( new && (!old) && rising ) trigger = 1;
    if ( old && (!new) && falling ) trigger = 1;
    data.old_in = new;
    /* is a pulse already running? */
    if ( data.timer > 0.0 ) {
	if ( ! retriggerable ) {
	    /* ignore edges during pulse */
	    trigger = 0;
	}
	/* decrement timer */
	data.timer -= period * 0.000000001;
	if ( data.timer < 0.0 ) data.timer = 0.0;
    }
    if ( trigger ) {
	/* (re)start pulse */
	data.timer = width;
    }
    /* drive outputs */
    time_left = data.timer;
    if ( data.timer > 0.0 ) {
	out = 1;
	out_not = 0;
    } else {
	out = 0;
	out_not = 1;
    }
}