// 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 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 in bit reset "Reset";
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;
if (reset) {
data.timer = 0.0;
data.old_in = 0;
out = 0;
out_not = 1;
return;
}
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;
}
}