www.pudn.com > fast.zip > v32tx.C

// #include  
#include  
 
#include  
#include  
#include  
#include  
#include  
 
#include "modem.h" 
#include "cancel.h" 
#include "coder.h" 
 
#define TX_TRNLEN   8000	/* length of training sequence transmitted (WAS 4096) */ 
 
static float shapetab[2*SYMBLEN+1] = 
  { /* Raised cosine pulse shaping with Beta = 0.5; square-root, with x/sinx compensation */ 
    +1.1510798492, +0.9848450677, +0.5795790021, +0.1495226763, 
    -0.1156411181, -0.1625782395, -0.0750914609, +0.0185567369, 
    +0.0448950047, 
  }; 
 
static sinegen *carrier; 
static coroutine *tx1_co, *tx2_co; 
static scrambler *gpc; 
static traininggen *trn; 
static encoder *enc; 
 
static void sendrate(ushort); 
static void tx2_loop(); 
static void sendsymbol(complex); 
 
inline void pbit(int b) { callco(tx2_co, b);	 } 
inline int gbit()	{ return callco(tx1_co); } 
 
 
global void inittx() 
  { carrier = new sinegen(1800.0); 
    tx1_co = currentco; 
    tx2_co = new coroutine(tx2_loop); 
    gpc = new scrambler(GPC); 
    trn = new traininggen(gpc); 
    enc = new encoder; 
    pbit(1);					    /* sync to symbol boundary */ 
    ushort r2 = rateword; 
    infomsg(">>> R2: rates = %04x", r2); 
    while (mstate < 5) sendrate(r2);		    /* send R2 */ 
    /* now rateword == R2 & R3 */ 
    rateword |= 0xf000; 
    /* pick highest common bit rate, leave just one rate bit set */ 
    if (rateword & rb_14400) rateword &= ~(rb_12000 | rb_9600 | rb_7200 | rb_4800); 
    else if (rateword & rb_12000) rateword &= ~(rb_9600 | rb_7200 | rb_4800); 
    else if (rateword & rb_9600) rateword &= ~(rb_7200 | rb_4800); 
    else if (rateword & rb_7200) rateword &= ~rb_4800; 
    else if (rateword & rb_4800) ; 
    else giveup("can't agree on a speed!"); 
    infomsg(">>> E2: rates = %04x", rateword);      /* send E2 */ 
    sendrate(rateword); 
    enc -> setrate(rateword);			    /* tell encoder what bit rate to use */ 
    while (mstate < 6) pbit(1);			    /* sync to Rx side */ 
    for (int i = 0; i < 128; i++) pbit(1);	    /* followed by 128 "1" bits */ 
  } 
 
static void sendrate(ushort wd) 
  { for (int i=0; i < 16; i++) { pbit(wd >> 15); wd <<= 1; } 
  } 
 
global void putasync(int n)			/* asynchronous output */ 
  { uint un = (n >= 0) ? (n << 1) | 0x200 :	/* add start bit, 1 stop bit */ 
			 0x3ff;			/* send mark bits while idle */ 
    until (un == 0) { pbit(un & 1); un >>= 1; } 
  } 
 
static void tx2_loop() 
  { /* round-trip-delay estimation */ 
    while (mstate < 2) 
      { complex z = (mstate == 0) ? ztab2[0] : ztab2[3];	/* A or C */ 
	sendsymbol(z); sendsymbol(z);	/* AA or CC */ 
      } 
    /* train equalizer */ 
    while (mstate == 2) sendsymbol(0.0); 
    /* train canceller */ 
    carrier -> resetphase(); 
    gpc -> reset();	/* reset scrambler before using trn */ 
    for (int bc = SEG_1; bc < SEG_3 + TX_TRNLEN; bc++) sendsymbol(trn -> get(bc)); 
    mstate++;		/* from 3 to 4 */ 
    /* exchange data */ 
    enc -> reset(); 
    for (;;) 
      { int bits = 0; 
	bits = (bits << 1) | gpc -> fwd(gbit()); 
	bits = (bits << 1) | gpc -> fwd(gbit()); 
	if (enc -> rate & rb_7200) bits = (bits << 1) | gpc -> fwd(gbit()); 
	sendsymbol(enc -> encode(bits)); 
      } 
  } 
 
static void sendsymbol(complex z) 
  { static complex a0 = 0.0, a1 = 0.0, a2 = 0.0, a3 = 0.0; 
    for (int k = 0; k < SYMBLEN; k++) 
      { /* baseband pulse shaping */ 
	complex s = shapetab[SYMBLEN + k]   * a0 
		  + shapetab[k]		    * a1 
		  + shapetab[SYMBLEN - k]   * a2 
		  + shapetab[2*SYMBLEN - k] * a3; 
	/* insert baseband sample into canceller */ 
	can -> insert(s); 
	/* modulate onto carrier */ 
	complex cz = carrier -> cnext(); 
	outsample(0.2f * (s.re*cz.re + s.im*cz.im)); 
      } 
    a0 = a1; a1 = a2; a2 = a3; a3 = z; 
  }