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/*

    CTCSS ... sub audio tone generator (replacement for Yaesu FTS-7)
    Target µC: ATtiny44

    Auf der IARU Konferenz in Südafrika wurde beschlossen alle FM Umsetzter bis Ende 2014 mit CTCSS Tönen
    auszustatten. Nach Möglichkeit sind die unten angeführten Töne zu verwenden:

    OE1    EIA 01    67,0 Hz
    OE2    EIA 08    88,5 Hz
    OE3    EIA 26    162,2 Hz
    OE4    EIA 11    84,8 Hz
    OE5    EIA 12    100,0 Hz
    OE6    EIA 13    103,5 Hz
    OE7    EIA 04    77,0 Hz
    OE8    EIA 08    88,5 Hz
    OE9    EIA 07    85,4 Hz
    
    Ausnahme: OE1XUU EIA26 162.2Hz

    Die CTCSS Frequenz kann über PA2..PA0 gewählt werden

        2012/10/07 OE1GCA, initial version
    2013/02/23 OE1GCA, changes for ATtiny44
    2013/05/09 OE1GCA, corrected fuse bits
    
        avr-gcc -mmcu=attiny44 ctcss_t44.c -o ctcss_t44
        avr-objcopy -O ihex ctcss_t44 ctcss_t44.hex
        avrdude -c stk500v2 -pt44 -P/dev/ttyUSB0 -U lfuse:w:0x7f:m -U hfuse:w:0xdc:m
        avrdude -c stk500v2 -pt44 -P/dev/ttyUSB0 -U flash:w:ctcss_t44.hex


    (c) 2012,2013 by OE1GCA
*/


#include <avr/io.h>
#include <stdio.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>


#define F_CPU 12000000UL      // 12 MHz
// fpwm = fclk / N*(1+TOP), where N is the prescaler (1, 8, 64, 256 or 1024)
// prescaler: 8


/* pwm sinus lookup table */
const uint16_t  SLUT_32[8][32] PROGMEM = {
/* 162.2 Hz */ {
145,173,200,225,247,265,278,286,289,286,278,265,247,225,200,173,145,116,89,64,42,24,11,3,0,3,11,24,42,64,89,116},
/* 67 Hz */ {
350,418,483,544,597,640,672,692,699,692,672,640,597,544,483,418,350,281,216,155,102,59,27,7,0,7,27,59,102,155,216,281},
/* 88.5 Hz */ {
265,316,366,411,452,484,509,524,529,524,509,484,452,411,366,316,265,213,163,118,77,45,20,5,0,5,20,45,77,118,163,213},
/* 84.8 Hz */ {
276,330,382,429,471,505,531,547,552,547,531,505,471,429,382,330,276,222,170,123,81,47,21,5,0,5,21,47,81,123,170,222},
/* 100 Hz */ {
234,280,324,364,399,429,450,464,468,464,450,429,399,364,324,280,234,188,144,104,69,39,18,4,0,4,18,39,69,104,144,188},
/* 103.5 Hz */ {
226,270,312,352,386,414,435,448,452,448,435,414,386,352,312,270,226,182,140,100,66,38,17,4,0,4,17,38,66,100,140,182},
/* 77 Hz */ {
304,363,420,473,519,557,585,602,608,602,585,557,519,473,420,363,304,245,188,135,89,51,23,6,0,6,23,51,89,135,188,245},
/* 85.4 Hz */ {
274,327,379,426,468,502,527,543,548,543,527,502,468,426,379,327,274,221,169,122,80,46,21,5,0,5,21,46,80,122,169,221}
};

/* frequency factor */
const uint16_t FLUT[8] PROGMEM = { 289, 699, 529, 552, 468, 452, 608, 548 };

/* Zugriff auf PROGMEM: pgm_read_byte (&SLUT_32[]); */

/*PWM Ausgang: OC1A (PA6) */


/* global variables */
unsigned char F = 0;

ISR(TIM1_OVF_vect) /* timer 1 overflow */
{
static int i=0;
unsigned int w;

    // update pwm register
    
    w = pgm_read_word (&SLUT_32[F][i]);
    OCR1AH = (unsigned char) (w>>8);
        OCR1AL = (unsigned char) w;
    i++;
    if (i > 31)
        i = 0;
    PORTA |= (1<<PA7);
    PORTA &= ~(1<<PA7);

}

int main(void){
unsigned char port,oldport=0;

    // setup direction=OUT, OC1A PWM output
    DDRA |= _BV(PA6);
    DDRA |= _BV(PA7);
    DDRB |= _BV(PB2);
    // enable pullups
    PORTA = ((1<<PA0) | (1<<PA1) | (1<<PA2) | (1<<PA3) | (1<<PA4) | (1<<PA5) | (1<<PA7));
    PORTB = (1<<PB2);    // unused pin
   
    // initialization of timer/counter1
    // mode = 14

    TCCR1A = (1<<WGM11) | (1<<COM1A1) | (1<<COM1A0); 
    TCCR1B = (1<<CS11) | (1<<WGM12) | (1<<WGM13);

    // set TOP value 

    F = (PINA & 0x07);     // read switch, ctcss f-selection 
    ICR1H = (unsigned char) (pgm_read_word (&FLUT[F])>>8);
    ICR1L = (unsigned char)  pgm_read_word (&FLUT[F]);
    
    // enable interrupt

    TIMSK1 = (1<<TOIE1);

    sei();

    while(1){
        port = PINA & (1<<PA3);        // RX/TX input 
        if (oldport != port) {
            oldport = port;
            if (port == 0) {
                PORTB |= (1<<PB2);
                sei();    // enable CTCSS output on TX
            }
            else {
                PORTB &= ~(1<<PB2);
                cli();    // disable CTCSS output on RX
            }
        }
    }
    return 0;
}