/******************************************************/
  /**      DDS Subtone Generator (c)2003 by SV6GMP     **/
 /**                 Stavros S. Fotoglou              **/
/******************************************************/
#include <io.h>
#include <interrupt.h>
#include <sig-avr.h>
#include <progmem.h>

#define TEST_TIM (1<<5)

#define SUBTONE_EN      (1<<0)
#define PTT_PRESSD      (1<<1)

typedef unsigned char u08;
typedef unsigned short u16;

void delay(u16);
// Sinus table
u08 __attribute__ ((progmem)) sinvals[] = {0,   //t0
                                           0,   //t1
                                           0,   //t2
                                           1,   //t3
                                           1,   //t4
                                           2,   //t5
                                           3,   //t6
                                           4,   //t7
                                           5,   //t8
                                           6,   //t9
                                           7,   //t10
                                           8,   //t11
                                          10,   //t12
                                          11,   //t13
                                          13,   //t14
                                          14,   //t15
                                          16,   //t16
                                          18,   //t17
                                          19,   //t18
                                          21,   //t19
                                          22,   //t20
                                          24,   //t21
                                          25,   //t22
                                          26,   //t23
                                          27,   //t24
                                          28,   //t25
                                          29,   //t26
                                          30,   //t27
                                          30,   //t28
                                          31,   //t29
                                          31,   //t30
                                          31};  //t31

u08 __attribute__ ((progmem)) divider[8][2] = {{0xfc, 0xf2},    //C-77
                                               {0xfd, 0x29},    //D-82,5
                                               {0xfd, 0x5c},    //E-88,5
                                               {0xfd, 0x73},    //--91,5
                                               {0xfd, 0x8b},    //F-94,8
                                               {0xfd, 0xc2},    //G-103,5
                                               {0xfd, 0xeb},    //H-110,9
                                               {0xfe, 0x10}};   //J-118,8


u08 s, tcnth, tcntl, flag;

SIGNAL(SIG_OVERFLOW1)
{
static u08 ti;
u08 ampl, idx;
//outp(0xfd, TCNT1H);
//outp(0xc4, TCNT1L);

outp(tcnth, TCNT1H);    //Reload timer, Hi byte first
outp(tcntl, TCNT1L);

s = inp(PORTB);
s = s & 0xe0;

if (s & TEST_TIM)
    s = s & (~TEST_TIM);
else
    s = s | TEST_TIM;


if (ti & 32)
    {
    idx = 31 - ti;
    }
else
    idx=ti;

idx = idx & 0x1f;

ampl = PRG_RDB(&sinvals[idx]);
ti=ti+1;
ampl = ampl & 0x1f;
if ((flag & SUBTONE_EN) && (flag & PTT_PRESSD))
    s = s | ampl;

outp(s, PORTB);
}

int main(void)
{
u08 dip;
outp(0xff, DDRB);       //Port B is output
outp(0xff, PORTB);      //All outs hi
outp(0, DDRD);          //Port D is input
outp(0x1f, PORTD);      //Pull up 5 lower bits
outp((1<<TOIE1), TIMSK); //Enable timer1 (16bit) interrupts
outp(0xfd, TCNT1H);
outp(0x5e, TCNT1L);
outp(1, TCCR1B);
outp(0, TCCR1A);
flag=0;
sei();

for(;;)
  {
  dip = inp(PIND);
  dip=~dip;

   if (dip & 8)
       flag |= SUBTONE_EN;
   else
       flag &= (~SUBTONE_EN);

   if (dip & 16)
       flag |= PTT_PRESSD;
   else
       flag &= (~PTT_PRESSD);

   dip = dip & 7;
   tcnth=PRG_RDB(&divider[dip][0]);
   tcntl=PRG_RDB(&divider[dip][1]);

   delay(1000);
   }
}

void delay(u16 imax)
{
u08 n;
u16 i;
for(i=0; i<imax; ++i)
    ++n;
}