progress_f.txt

Fax and soft modem source code. - Slow modem You can use this code to build a soft modem function

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	progress_F.txt
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/* Modem for MIPS   AJF	  January 1995
   Wait for tone (dial, connect, etc.) */

#include <stdio.h>
#include <math.h>

#include <complex.h>
#include <filters.h>
#include <myaudio.h>
#include <tonedec.h>

#include "modem.h"

#define debug_cadence false

struct cadence_detector
  { cadence_detector()
      { pcnt = acnt = 0;	    /* sample counts */
	oncount = offcount = 0;	    /* cadence on/off counts */
      }
    void insert(bool);
    void debug();
    int oncount, offcount;
private:
    int pcnt, acnt;
  };

/* Filter coeffs constructed by:
   mkfilter -Bu -Bp -o 2 -a (A1) (A2)
   where A1 = F1 / SAMPLERATE, A2 = F2 / SAMPLERATE
   Indexed by tone; see modem.h */

static fspec *bpfspecs[] =
  { mkfilter("-Bu -Bp -o 2 -a 0.04062500000 0.04270833333"),        /*  390 ..  410 Hz, centre  400 Hz    [0]        */
    mkfilter("-Bu -Bp -o 2 -a 0.04583333333 0.04791666667"),        /*  440 ..  460 Hz, centre  450 Hz    [1] (dial) */
    mkfilter("-Bu -Bp -o 2 -a 0.21770833333 0.21979166667"),        /* 2090 .. 2110 Hz, centre 2100 Hz    [2] (conn) */
  };

static fspec *fefs = mkfilter("-Hp -Bu -o 2 -a 0.03125");           /* 300 Hz hpf */
static fspec *lpfs = mkfilter("-Bu -Lp -o 2 -a 0.004166666667");    /*  40 Hz lpf */

inline int secs(float f) { return (int) (f * SAMPLERATE); }


global void waitfortone(int tone)
  { tone_detector
	*td1 = new tone_detector(fefs, bpfspecs[0], lpfs, true),
	*td2 = new tone_detector(fefs, bpfspecs[tone], lpfs, true);
    cadence_detector
	*cd1 = new cadence_detector(),
	*cd2 = new cadence_detector();
    int totcount = 0;
    bool found = false;
    until (found)
      { float x = insample();
	td1 -> insert(x); cd1 -> insert(td1 -> present);
	td2 -> insert(x); cd2 -> insert(td2 -> present);
	if (debug_cadence && totcount%500 == 0)
	  { td1 -> debug(); cd1 -> debug();
	    td2 -> debug(); cd2 -> debug();
	    putc('\n', stderr);
	  }
	switch (tone)
	  { case DIAL_TONE:
		if (totcount >= secs(5.0f)) giveup("No dial tone");
		if (td2 -> prescount > secs(1.5f)) found = true;
		break;

	    case CONN_TONE:
		if (totcount % secs(3.5f) == 0)
		  { /* send CNG or V.25 CT every 3.5 secs */
		    float f = (options & opt_fax) ? 1100.0 : 1300.0;
		    sendfreq(f, 0.5f);
		  }
		if (totcount >= secs(45.0f)) giveup("No reply"); /* long delay in case there's an answering m/c */
		if ((td2 -> prescount > secs(2.7f)) || (cd2 -> oncount > 6)) found = true;	/* V.25, V.25 bis */
		break;
	  }
	if (td1 -> prescount >= secs(3.0f)) giveup("Number unobtainable");
	if (cd1 -> oncount >= 4 && cd1 -> offcount >= 4) giveup("Number busy");
	totcount++;
      }
    delete td1; delete td2; delete cd1; delete cd2;
  }

void cadence_detector::insert(bool pres)
  { if (pres)
      { pcnt++;
	if (acnt >= secs(0.25f) && acnt <= secs(0.55f)) offcount++;	/* 0.25 was 0.3 */
	acnt = 0;
      }
    else
      { acnt++;
	if (pcnt >= secs(0.25f) && pcnt <= secs(0.55f)) oncount++;	/* 0.25 was 0.3 */
	pcnt = 0;
      }
  }

void cadence_detector::debug()
  { fprintf(stderr, " [%d:%d]", offcount, oncount);
  }