RDS Text auf RDS Radio Display / GC Station

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


// Hardware connections:
// 20 pin ATtiny 2313

// pin 5  XTAL1  input  : 11.592 MHz VXCO clock input
// pin 6  PD2    output : 57 kHz interrupt signal
// pin 7  PD3    output : RDS Bit Clock 1.1875kHz
// pin 8  PD4    output : CRC-Calc active high
// pin 9  PD5    output : Frame-sync for test-sequence
// pin 12 PB0    input  : TA traffic-announcement, low-active
// pin 13 PB1    input  : TP traffic-programme, high-active
// pin 14 PB2    input  : set Test-Mode, low-active
// pin 15 PB3 (OC1A) out: RDS modulation signal


// parameters for 11.0592 MHz clock
// 11.059200MHz/57kHz=194.021052.... truncated gives 194
//   0.021052...*2^15=689.85...      rounded gives 690


// this is the fractional value for PWM adjustment
#define deltaDDS 690

// the following two values are used for PWM control
#define TOP1 194 
#define TOP2 193 

// this defines the middle of the pwm signal, approximately 50 % duty cycle
#define MIDTH 97

// change PWM polarity by switching between these two values
#define MODE1 0b10000010 
#define MODE2 0b11000010

uint16_t DDS ;            // fractional 57kHz generation adder
uint8_t  BITtimer ;       // count 57 kHz cycles
uint16_t ShiftReg ;       // shift out RDSbits MSB first
uint16_t HoldReg ;        // hold register loads shift register
uint8_t  BitsInShiftReg ; // bits left to shift out
uint8_t  BitsInHoldReg ;  // bits copied into shift-register

uint8_t RDSbit ;          // differentially coded bit stream enters here, value 0 or 1 !!


// intrrupt rate is 57 kHz !!


ISR(TIMER1_OVF_vect) {
	asm volatile (" sbi 18,2 \n\t" ) ; 	// 18=PORTD  , signal interrupt on PD.2


// 15 bit DDS fractional generator
	DDS += deltaDDS ;
	if (DDS & 0x8000 )  { 
		ICR1 =TOP1 ;  }    // on overflow change PWM width
	  else { 
	    ICR1 =TOP2  ;} ; 
	DDS &=0x7fff ;         // wrap around

	 
	BITtimer++ ;
	if (BITtimer==24) { 
		asm volatile (" sbi 18,3 \n\t" ) ; 
		asm volatile (" sbi 18,5 \n\t" ) ; 	// 18=PORTD  	
		if (ShiftReg & 0x8000 ) { 
			RDSbit=1-RDSbit ; } ;
		if (RDSbit) { TCCR1A=MODE1 ; } else { TCCR1A=MODE2 ; } ;
		ShiftReg=ShiftReg<<1 ;
		BitsInShiftReg-- ;
	
		}
	  else if (BITtimer==48) { 
	 	BITtimer=0 ;  
		asm volatile (" cbi 18,3 \n\t" ) ; 	
		if (RDSbit) { TCCR1A=MODE2 ; } else { TCCR1A=MODE1 ; } ;
		if (BitsInShiftReg==0) { 
			BitsInShiftReg=BitsInHoldReg ; 
			ShiftReg=HoldReg ; 
			BitsInHoldReg=0 ; }
		} ;

	asm volatile (" cbi 18,2 \n\t" ) ; 		// 18=PORTD	signal end interrupt on PD.2
}




uint16_t Syndrom ; // rightmost 10 bits used ;

void PutBlock(uint16_t w , uint16_t ofs){
uint8_t j ;
	while(BitsInHoldReg!=0){} ; HoldReg=w ; BitsInHoldReg=16 ;
	
/**/asm volatile (" sbi 18,4 \n\t" ) ; 	// 18=PORTD  
	Syndrom=0 ;
	for (j=0 ; j<16 ; j++) {
		Syndrom=Syndrom<<1 ; // outgoing bi is at mask 0x0400
		if (w & 0x8000) { Syndrom ^= 0x0400 ; } // exor into outgoing bit
		w=w<<1 ;
		if ( Syndrom & 0x0400 ) { Syndrom ^= 0x1B9 ; }
		} ;
    Syndrom=(Syndrom^ofs)<<6 ;
/**/asm volatile (" cbi 18,4 \n\t" ) ; 	// 18=PORTD  

	while(BitsInHoldReg!=0){} ; HoldReg=Syndrom ; BitsInHoldReg=10 ;
	}


void SendGroup(uint16_t a,uint16_t b,uint16_t c,uint16_t d){
	PutBlock(a,0x00fc) ; // block A
	PutBlock(b,0x0198) ; // block B
	PutBlock(c,0x0168) ; // block C
	PutBlock(d,0x01b4) ; // block D
	} 


void send_test(){
	asm volatile (" cbi 18,5 \n\t" ) ; 	// 18=PORTD  
	while(BitsInHoldReg!=0){} ; 
	HoldReg=0x8CF8 ; BitsInHoldReg=16 ;
	}

char name[] = "ELEKTOR.";         // im RAM !!
char text[] = "RADIOTEXT IST OK"; // im RAM !!
uint8_t ms ;
uint8_t ta ;
uint8_t tp ;
uint16_t blkB ;

#define AFfiller 0xCDCD
#define PIcode   0x1234
#define GRP0A    0x0000
#define GRP2A    0x2000
#define PTY      0x1

void send_group0(uint8_t k){
	blkB=(PTY<<5)+(ms<<3)+(tp<<10)+(ta<<4) ;
	SendGroup(PIcode,blkB+GRP0A+k, AFfiller, name[2*k+1]+(name[2*k+0]<<8) ) ;	
}

void send_group2(uint8_t k){
	blkB=(PTY<<5)+(tp<<10) ;
	SendGroup(PIcode,blkB+GRP2A+k, text[4*k+1]+(text[4*k+0]<<8),text[4*k+3]+(text[4*k+2]<<8)) ;
}


int main(){

  DDRD =0b11111100 ; // enable outputs , bit 0,1=input
  PORTD=0b11111111 ; // pullups on on input pins
  
  DDRB =0b11111000 ; // enable outputs , bits 0,1 input
  PORTB=0b11111111 ; // pullups on on input pins
  

  					  // TIMER1 settings
  TCCR1A=0b10000010 ; // fast PWM TOP=ICR1
  TCCR1B=0b00011001	; // ck=XTAL
  OCR1A=MIDTH ;       // approx 1:1 duty cycle
  ICR1 = TOP1 ;       // TOP for fast PWM

  RDSbit=0 ;
  BITtimer=0 ;
  HoldReg=0x7 ;
  // Interupt enable for Timer1-Overflow 0100B 
  // TIMSK=0b00000100 ; // atmetga 8
  TIMSK=0b10000000 ; // at tiny 2313
  sei() ;


  while(1){ 
    ms=1 ;
	
    if (PINB & 1) { ta=0 ; } else { ta=1 ; } ;
	if (PINB & 2) { tp=1 ; } else { tp=0 ; } ;
	if (PINB & 4) {
		send_group0(0) ;
		send_group0(1) ;
		send_group0(2) ;
		send_group0(3) ;

		send_group2(0) ;
		send_group2(1) ;
		send_group2(2) ;
		send_group2(3) ;
		}
	  else {
	    send_test() ;
		}

	} ;
  return(0) ;
 }