Re: [Gnucap-devel] qucs parser

[al davis]

On Thursday 15 March 2012, Felix Salfelder wrote:
> We have mostly figured out the parser and the parameter
> passing. it works in some examples. others should work after
> completing the corresponding set_param* functions.

Good .. I think the qucs people will like it too.

> what remains (on gnucap side) is the probes. qucs does not
> issue .print commands, but has {i,v} probe devices, which
> add themselves to the printlist. we had no trouble to
> implement an ELEMENT doing, what the qucs-style probes do
> and hacked a simple hook in the backend, which makes these
> probes register the corresponding probes.

In a way, I like the qucs approach that everything, including 
probes, is a netlist element.  A while back, I implemented a 
"meter" device that provides some new probes like "gain".

If all you can look at is voltage and current, the idea of all 
probes are elements is a good one.  But there is a lot more to 
probe than voltage and current.  .. things like gm or ft of a 
transistor, instantaneous capacitance of a diode used as a 
variable capacitor ....

One thought is to make a "wire" or "net" a first class object.  
A wire could be perfect, and give you a bunch of probes, or it 
could have electrical characteristics like resistance or delay.  
I think this is needed anyway, for schematic and layout interface.

> there seem to be hardly any more options (we don't want to
> change qucs for that matter), and i like the idea of having
> devices add probes. would you give a hint on how to
> implement this functionality without breaking other things?
> i'd like to add this functionality, but i'm not feeling
> creative...

Here's the code for a "meter" device.  It adds a "gain" probe, 
and inherits all of the probes than an ELEMENT has.


/*$Id$ -*- C++ -*-
 * Copyright (C) 2010 Albert Davis
 * Author: Albert Davis <address@hidden>
 *
 * This file is part of "Gnucap", the Gnu Circuit Analysis Package
 *
 * 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 3, 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.
 *------------------------------------------------------------------
 * 2-port "meter" device
 * does nothing to the circuit, but has probes
 */
#include "globals.h"
#include "e_elemnt.h"
#include "u_xprobe.h"
/*--------------------------------------------------------------------------*/
namespace {
/*--------------------------------------------------------------------------*/
class DEV : public ELEMENT {
private:
  explicit DEV(const DEV& p) :ELEMENT(p) {}
public:
  explicit DEV()                :ELEMENT() {}
private: // override virtual
  char     id_letter()const     {return '\0';}
  std::string value_name()const {return "";}
  std::string dev_type()const   {return "meter";}
  int      max_nodes()const     {return 4;}
  int      min_nodes()const     {return 4;}
  int      matrix_nodes()const  {return 4;}
  int      net_nodes()const     {return 4;}
  CARD*    clone()const         {return new DEV(*this);}
  void     tr_iwant_matrix()    {}
  void     ac_iwant_matrix()    {}
  void     precalc_last();
  double   tr_involts()const    {return dn_diff(_n[IN1].v0(), _n[IN2].v0());}
  double   tr_involts_limited()const {return tr_involts();}
  COMPLEX  ac_involts()const    {return _n[IN1]->vac() - _n[IN2]->vac();}
  double   tr_probe_num(const std::string&)const;
  XPROBE   ac_probe_ext(const std::string&)const;

  std::string port_name(int i)const {
    assert(i >= 0);
    assert(i < 4);
    static std::string names[] = {"outp", "outn", "inp", "inn"};
    return names[i];
  }
};
/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/
void DEV::precalc_last()
{
  ELEMENT::precalc_last();
  set_constant(true);
  set_converged();
}
/*--------------------------------------------------------------------------*/
double DEV::tr_probe_num(const std::string& x)const
{
  if (Umatch(x, "gain ")) {
    return tr_outvolts() / tr_involts();
  }else{
    return ELEMENT::tr_probe_num(x);
  }
}
/*--------------------------------------------------------------------------*/
XPROBE DEV::ac_probe_ext(const std::string& x)const
{
  if (Umatch(x, "gain ")) {
    return XPROBE(ac_outvolts() / ac_involts());
  }else{
    return ELEMENT::ac_probe_ext(x);
  }
}
/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/
DEV p1;
DISPATCHER<CARD>::INSTALL d1(&device_dispatcher, "meter", &p1);
}
/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/