Hi guys, I have a max external that I need to port to pd to put it on raspberry pi. I don't have the time to do it myself. Anybody can help me? I have a little budget for it. I attach the code.vb.fourses~.c

Edit 1: Took a shot porting it in this little textarea. Probably doesn't compile yet...
Edit 2: Ok, this should compile now. I haven't actually tried to instantiate it yet, though. It's possible I set it up with the wrong number of xlets.
Edit 3: Seems to instantiate ok. It appears it doesn't take signal input so the CLASS_MAINSIGNALIN macro is neccessary. Just comment that part out to make it a control signal.

Note-- in my port it's called [vb_fourses~] for the reason noted below.

I have no idea if the algorithm behaves correctly, but it does output sound.

Btw-- AFAICT you should be able to compile this external for the 64-bit version of Purr Data and it should work properly. It doesn't require a special 64-bit codepath in Pd so I commented that part out.

Btw 2-- there should probably be a "best practices" rule that states you can only name your class something that is a legal C function name. Because this class doesn't follow that practice I made a mistake in the port. Further, the user will make a mistake because I had to change the class name. If I had instead made the setup function a different name than the creator I would create an additional problem that would force users to declare the lib before using it. Bad all around, and not worth whatever benefit there is to naming a class "foo.bar" instead of "foo_bar"

/*
#include "ext.h"
#include "ext_obex.h"
#include "z_dsp.h"
#include "ext_common.h"
*/

#include "m_pd.h"
#include "math.h"

/*
    a chaotic oscillator network
    based on descriptions of the 'fourses system' by ciat-lonbarde 
    www.ciat-lonbarde.net
 
    07.april 2013, volker b?hm
*/

#define NUMFOURSES 4

static void *myObj_class;

typedef struct {
    // this is a horse... basically a ramp generator
    double      val;
    double      inc;
    double      dec;
    double      adder;
    double      incy, incym1;       // used for smoothing
    double      decy, decym1;       // used for smoothing
} t_horse;

typedef struct {
    t_object    x_obj;
    double      r_sr;
    t_horse     fourses[NUMFOURSES+2];  // four horses make a fourse...
    double      smoother;
    t_sample x_f;
} t_myObj;


// absolute limits
static void myObj_hilim(t_myObj *x, t_floatarg input);
static void myObj_lolim(t_myObj *x, t_floatarg input);

// up and down freqs for all oscillators
static void myObj_upfreq(t_myObj *x, t_floatarg freq1, t_floatarg freq2, t_floatarg freq3, t_floatarg freq4);
static void myObj_downfreq(t_myObj *x, t_floatarg freq1, t_floatarg freq2, t_floatarg freq3, t_floatarg freq4);

static void myObj_smooth(t_myObj *x, t_floatarg input);
static void myObj_info(t_myObj *x);

// DSP methods
static void myObj_dsp(t_myObj *x, t_signal **sp);
static t_int *myObj_perform(t_int *w);
//void myObj_dsp64(t_myObj *x, t_object *dsp64, short *count, double samplerate, 
//               long maxvectorsize, long flags);
//void myObj_perform64(t_myObj *x, t_object *dsp64, double **ins, long numins, 
//                     double **outs, long numouts, long sampleframes, long flags, void *userparam);
//

static void *myObj_new( t_symbol *s, int argc, t_atom *argv);
//void myObj_assist(t_myObj *x, void *b, long m, long a, char *s);


void vb_fourses_tilde_setup(void) {
    t_class *c;
    myObj_class = class_new(gensym("vb_fourses~"), (t_newmethod)myObj_new, 0, sizeof(t_myObj), 
                  0, A_GIMME, NULL);
    c = myObj_class;
    class_addmethod(c, (t_method)myObj_dsp, gensym("dsp"), A_CANT, 0);
//  class_addmethod(c, (t_method)myObj_dsp64, gensym("dsp64"), A_CANT, 0);
    class_addmethod(c, (t_method)myObj_smooth, gensym("smooth"), A_FLOAT, 0);   
    class_addmethod(c, (t_method)myObj_hilim, gensym("hilim"), A_FLOAT, 0);
    class_addmethod(c, (t_method)myObj_lolim, gensym("lolim"), A_FLOAT, 0);
    class_addmethod(c, (t_method)myObj_upfreq, gensym("upfreq"), A_FLOAT, A_FLOAT, A_FLOAT, A_FLOAT, 0);
    class_addmethod(c, (t_method)myObj_downfreq, gensym("downfreq"), A_FLOAT, A_FLOAT, A_FLOAT, A_FLOAT, 0);
     
    class_addmethod(c, (t_method)myObj_info, gensym("info"), 0);
    //class_addmethod(c, (t_method)myObj_assist, "assist", A_CANT,0);
    CLASS_MAINSIGNALIN(myObj_class, t_myObj, x_f);
//  class_dspinit(c);
//  class_register(CLASS_BOX, c);   
    
    post("vb_fourses~ by volker b?hm\n");
    
//  return 0;
}


static void myObj_smooth(t_myObj *x, t_floatarg input) {
//  input = CLAMP(input, 0., 1.);
   if (input < 0.) input = 0;
     if (input > 1.) input = 1;
    x->smoother = 0.01 - pow(input,0.2)*0.01;
}

static void myObj_hilim(t_myObj *x, t_floatarg input) {
    x->fourses[0].val = input;      // store global high limit in fourses[0]
}
static void myObj_lolim(t_myObj *x, t_floatarg input) { 
    x->fourses[5].val = input;      // store global low limit in fourses[5]
}

static void myObj_upfreq(t_myObj *x, t_floatarg freq1, t_floatarg freq2, t_floatarg freq3, t_floatarg freq4) {
    x->fourses[1].inc = fabs(freq1)*4*x->r_sr;
    x->fourses[2].inc = fabs(freq2)*4*x->r_sr;
    x->fourses[3].inc = fabs(freq3)*4*x->r_sr;
    x->fourses[4].inc = fabs(freq4)*4*x->r_sr;
}

static void myObj_downfreq(t_myObj *x, t_floatarg freq1, t_floatarg freq2, t_floatarg freq3, t_floatarg freq4) {
    x->fourses[1].dec = fabs(freq1)*-4*x->r_sr;
    x->fourses[2].dec = fabs(freq2)*-4*x->r_sr;
    x->fourses[3].dec = fabs(freq3)*-4*x->r_sr;
    x->fourses[4].dec = fabs(freq4)*-4*x->r_sr;
}


//#pragma mark 64bit dsp-loop ------------------

//void myObj_dsp64(t_myObj *x, t_object *dsp64, short *count, double samplerate, 
//               long maxvectorsize, long flags) {
//  object_method(dsp64, gensym("dsp_add64"), x, myObj_perform64, 0, NULL);
//  
//  if(samplerate<=0) x->r_sr = 1.0/44100.0;
//  else x->r_sr = 1.0/samplerate;
//  
//  
//}

//static void myObj_perform64(t_myObj *x, t_object *dsp64, double **ins, long numins, 
//                     double **outs, long numouts, long sampleframes, long flags, void *userparam){
//  
//  t_double **output = outs;
//  int vs = sampleframes;  
//  t_horse *fourses = x->fourses;
//  double val, c, hilim, lolim;
//  int i, n;
//  
//  if (x->x_obj.z_disabled)
//      return;
//
//  c = x->smoother;
//  hilim = fourses[0].val;
//  lolim = fourses[5].val;
//  
//  for(i=0; i<vs; i++) 
//   {
//      for(n=1; n<=NUMFOURSES; n++) {
//          // smoother
//          fourses[n].incy = fourses[n].inc*c + fourses[n].incym1*(1-c);
//          fourses[n].incym1 = fourses[n].incy;
//          
//          fourses[n].decy = fourses[n].dec*c + fourses[n].decym1*(1-c);
//          fourses[n].decym1 = fourses[n].decy;
//          
//          val = fourses[n].val;
//          val += fourses[n].adder;
//
//          if(val <= fourses[n+1].val || val <= lolim ) {
//              fourses[n].adder = fourses[n].incy;
//          }
//          else if( val >= fourses[n-1].val || val >= hilim ) {
//              fourses[n].adder = fourses[n].decy;
//          }
//      
//          output[n-1][i] = val;
//          
//          fourses[n].val = val;
//      }
//   }
//  
//  return;
//  
//}

//#pragma mark 32bit dsp-loop ------------------

static void myObj_dsp(t_myObj *x, t_signal **sp) 
{   
    dsp_add(myObj_perform, 6, x, sp[0]->s_vec, sp[1]->s_vec, sp[2]->s_vec, sp[3]->s_vec, sp[0]->s_n);
    
    if(sp[0]->s_sr<=0) 
        x->r_sr = 1.0/44100.0;
    else x->r_sr = 1.0/sp[0]->s_sr; 
}


static t_int *myObj_perform(t_int *w) 
{   
    t_myObj *x = (t_myObj*)(w[1]);
    t_float *out1 = (float *)(w[2]);
    t_float *out2 = (float *)(w[3]);    
    t_float *out3 = (float *)(w[4]);
    t_float *out4 = (float *)(w[5]);    
    int vs = (int)(w[6]);       
    
// Hm... not sure about this member. I don't think we can disable individual
// objects in Pd...
//    if (x->x_obj.z_disabled)
//        goto out;
    
    t_horse *fourses = x->fourses;
    double val, c, hilim, lolim;
    int i, n;
    
    c = x->smoother;
    hilim = fourses[0].val;
    lolim = fourses[5].val;
    
    for(i=0; i<vs; i++) 
     {
        for(n=1; n<=NUMFOURSES; n++) {
            // smoother
            fourses[n].incy = fourses[n].inc*c + fourses[n].incym1*(1-c);
            fourses[n].incym1 = fourses[n].incy;
            
            fourses[n].decy = fourses[n].dec*c + fourses[n].decym1*(1-c);
            fourses[n].decym1 = fourses[n].decy;
            
            val = fourses[n].val;
            val += fourses[n].adder;
            
            if(val <= fourses[n+1].val || val <= lolim ) {
                fourses[n].adder = fourses[n].incy;
            }
            else if( val >= fourses[n-1].val || val >= hilim ) {
                fourses[n].adder = fourses[n].decy;
            }
            
            fourses[n].val = val;
        }
        
        out1[i] = fourses[1].val;
        out2[i] = fourses[2].val;
        out3[i] = fourses[3].val;
        out4[i] = fourses[4].val;
         
     }
//out:
    return w+7; 
}

static void myObj_info(t_myObj *x) {
    int i;
    // only fourses 1 to 4 are used
    post("----- fourses.info -------");
    for(i=1; i<=NUMFOURSES; i++) {
        post("fourses[%ld].val = %f", i, x->fourses[i].val);
        post("fourses[%ld].inc = %f", i, x->fourses[i].inc);
        post("fourses[%ld].dec = %f", i, x->fourses[i].dec);
        post("fourses[%ld].adder = %f", i, x->fourses[i].adder);
    }   
    post("------ end -------");
}

void *myObj_new(t_symbol *s, int argc, t_atom *argv)
{
    t_myObj *x = (t_myObj *)pd_new(myObj_class);
//  dsp_setup((t_pxobject*)x, 0);           
    outlet_new((t_object *)x, &s_signal); 
    outlet_new((t_object *)x, &s_signal); 
    outlet_new((t_object *)x, &s_signal); 
    outlet_new((t_object *)x, &s_signal); 
    
    x->r_sr = 1.0/sys_getsr();
    if(sys_getsr() <= 0)
        x->r_sr = 1.0/44100.f;
    
    int i;
    for(i=1; i<=NUMFOURSES; i++) {
        x->fourses[i].val = 0.;
        x->fourses[i].inc = 0.01;
        x->fourses[i].dec = -0.01;
        x->fourses[i].adder = x->fourses[i].inc;
        
    }
    x->fourses[0].val = 1.; // dummy 'horse' only used as high limit for fourses[1]
    x->fourses[5].val = -1.;    // dummy 'horse' only used as low limit for fourses[4]

    x->smoother = 0.01; 
    
    return x;
}


//void myObj_assist(t_myObj *x, void *b, long m, long a, char *s) {
//  if (m==1) {
//      switch(a) {
//          case 0: sprintf (s,"message inlet"); break;
//      }
//  }
//  else {
//      switch(a) {
//          case 0: sprintf (s,"(signal) signal out osc1"); break;
//          case 1: sprintf(s, "(signal) signal out osc2"); break;
//          case 2: sprintf(s, "(signal) signal out osc3"); break;
//          case 3: sprintf(s, "(signal) signal out osc4"); break;
//      }
//      
//  }
//}

Btw-- If you want a binary for the RPI3 I can post one later.