tips suggestions SPI-->I2C

That´s a code for making data aquisition from a chip through SPI of a
mega16 and then I want to sent the data through I2C in a mega128. If
you see some "illigal" things or something that is not going well
please let me know. I can´t try to interface it to see if it works
because I need at least 50-70€ to make the pcd. Thanks a lot for your
try and your time!!

Code:

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#include <mega16.h>
// SPI functions
#include <spi.h>
#include <stdio.h>
#include <stdlib.h>                                 


// Declare your global variables here
           

//#define TWCR    _SFR_IO8(0x36)
#define AD7708_CS PORTA.3

#define TWIE    0
#define TWEN    2
#define TWWC    3
#define TWSTO  4
#define TWSTA  5
#define TWEA    6
#define TWINT  7

#define TWI_START                  0x08  // START has been transmitted 
#define SLA_W                      0x20  // Slave address 0x10 + 0 write bit           
#define MT_SLA_ACK                0x18
#define MT_DATA_ACK                0x28     
#define TWI_BUFFER_SIZE            100             
                                 
unsigned char TWI_Buffer[TWI_BUFFER_SIZE+1];
unsigned int TWI_Wr_Index;
unsigned int TWI_Rd_Index;
unsigned int TWI_Counter;
unsigned int h,g;         
unsigned char c;   
                 

void SPI_to_BuFF (void)
 {
    //unsigned char  c;
    c = SPDR;
    TWI_Buffer[TWI_Wr_Index++] = c;
    if (TWI_Wr_Index > TWI_BUFFER_SIZE)
        TWI_Wr_Index = 0;
    if (++TWI_Counter > TWI_BUFFER_SIZE)
        {
 
            TWI_Counter = TWI_BUFFER_SIZE;
            //TWI_Buffer_Overflow = 1;
            printf("overflow");
     
        }; 
   
     
  }         

unsigned char message (void)
{
    g = h;
    TWDR = g;
}                                             
 
void SPI_MasterDataReceive(void)
{
    SPDR=0x00;//Trigger first transaction
    while(!(SPSR&0x80)); //wait for transmission   
    c=SPDR; //fetch first 8 bits from the ADC
}


// External Interrupt 0 service routine
interrupt [EXT_INT0] void ext_int0_isr(void)
{
      // Place your code here
      int reg1;
      //
      //  8  To write to the Communication Register to go to the ADC Control register
      //
     
      SPDR = 0x02;        //communications register
      while((SPSR&0x80)==0);
      SPDR = 0x7F;        //  8  To write to the ADC Control register my parameters
      while((SPSR&0x80)==0);
     
      //
      //  8  To read  the Status register 
      //
      SPDR = 0x40;        //communications register = read of data reg
      while((SPSR&0x80)==0);
      SPDR = 0x00;
      while((SPSR&0x80)==0);
      reg1 = SPDR;
 
      //reg1 the data which come from the Ad7708(to make the data aqui in the Status Reg the flag mustn`t be set)

     
          if (reg1<128)
              {
                    //
                    //  8  To read(dataq) the 8th ch
                    //
       
                    SPDR = 0x44;        //communications register = read of data reg
                    while((SPSR&0x80)==0);
                   
                   
                    SPI_MasterDataReceive();
                    SPI_to_BuFF();
               
              }
   
}



// 2 Wire bus interrupt service routine
interrupt [TWI] void twi_isr(void)
{         
    if ( TWI_Counter != 0 )
    {
        h = TWI_Buffer[TWI_Rd_Index];
        if (++TWI_Rd_Index > TWI_BUFFER_SIZE)
          TWI_Rd_Index = 0;
        TWI_Counter--; 
       
    }
   
    resend_again:
    message();   
    //TWDR=SPDR 
    TWCR = (1<<TWINT)|(1<<TWEN); /* Clear TWI INT flag to start transmission*/
    while (!(TWCR & (1<<TWINT)));
    if ((TWSR & 0xF8) !=MT_DATA_ACK)
    {
       
        goto resend_again;
       
    };
}



// Declare your global variables here

void main(void)
{
// Declare your local variables here

// Input/Output Ports initialization
// Port A initialization
// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTA=0x00;
DDRA=0x00;

// Port B initialization
// Func7=Out Func6=In Func5=Out Func4=Out Func3=In Func2=In Func1=In Func0=In
// State7=0 State6=T State5=0 State4=0 State3=T State2=T State1=T State0=T
PORTB=0x00;
DDRB=0xB0;

// Port C initialization
// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTC=0x00;
DDRC=0x00;

// Port D initialization
// Func7=In Func6=In Func5=In Func4=In Func3=In Func2=In Func1=In Func0=In
// State7=T State6=T State5=T State4=T State3=T State2=T State1=T State0=T
PORTD=0x00;
DDRD=0x00;

// Timer/Counter 0 initialization
// Clock source: System Clock
// Clock value: Timer 0 Stopped
// Mode: Normal top=FFh
// OC0 output: Disconnected
TCCR0=0x00;
TCNT0=0x00;
OCR0=0x00;

// Timer/Counter 1 initialization
// Clock source: System Clock
// Clock value: Timer 1 Stopped
// Mode: Normal top=FFFFh
// OC1A output: Discon.
// OC1B output: Discon.
// Noise Canceler: Off
// Input Capture on Falling Edge
TCCR1A=0x00;
TCCR1B=0x00;
TCNT1H=0x00;
TCNT1L=0x00;
ICR1H=0x00;
ICR1L=0x00;
OCR1AH=0x00;
OCR1AL=0x00;
OCR1BH=0x00;
OCR1BL=0x00;

// Timer/Counter 2 initialization
// Clock source: System Clock
// Clock value: Timer 2 Stopped
// Mode: Normal top=FFh
// OC2 output: Disconnected
ASSR=0x00;
TCCR2=0x00;
TCNT2=0x00;
OCR2=0x00;

// External Interrupt(s) initialization
// INT0: On
// INT0 Mode: Falling Edge
// INT1: Off
// INT2: Off
GICR|=0x40;
MCUCR=0x02;
MCUCSR=0x00;
GIFR=0x40;

// Timer(s)/Counter(s) Interrupt(s) initialization
TIMSK=0x00;

// Analog Comparator initialization
// Analog Comparator: Off
// Analog Comparator Input Capture by Timer/Counter 1: Off
ACSR=0x80;
SFIOR=0x00;

// SPI initialization
// SPI Type: Master
// SPI Clock Rate: 2*3686,400 kHz
// SPI Clock Phase: Cycle Half
// SPI Clock Polarity: Low
// SPI Data Order: MSB First
SPCR=0x50;
SPSR=0x01;

// 2 Wire Bus initialization
// Generate Acknowledge Pulse: On
// 2 Wire Bus Slave Address: 10h
// General Call Recognition: Off
// Bit Rate: 388,042 kHz
TWSR=0x00;
TWBR=0x0B;
TWAR=0x20;
TWCR=0x45;
 


// Global enable interrupts
#asm("sei")

    start_again:
    TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);
    while (!(TWCR & (1<<TWINT)));             
    if ((TWSR & 0xF8) != TWI_START)
    { 
   
        goto start_again;
       
    };

    repeat_again: 
    TWDR = SLA_W;
    TWCR = (1<<TWINT)|(1<<TWEN);
    while (!(TWCR & (1<<TWINT)));
    if ((TWSR & 0xF8) != MT_SLA_ACK)
    {
       
        goto repeat_again;
       
    };   




  //
  //    To write to the Communication Register to go to the IO Register
  //
 
  SPDR = 0x00;
  //reg &= 0x07;
  PORTA &= ~(1<<AD7708_CS); //CS low
  SPDR = 0x07;       
  while((SPSR&0x80)==0); //wait for transmition to complete
  //reg = SPDR;
  SPDR = 0x02;          //    To write to the IO Register ???!!!!!!!!
  while((SPSR&0x80)==0);
  //reg = SPDR;
  //PORTA |= (1<<AD7708_CS); //CS high
 
 
  //    To write to the Communication Register to go to the Mode Register
  //
  //reg &= 0x01;
  //PORTA &= ~(1<<AD7708_CS); //CS low
  SPDR = 0x01 ;        //communications register
  while((SPSR&0x80)==0);
  //reg = SPDR ;
  SPDR = 0x83;
  while((SPSR&0x80)==0);
  //reg = SPDR;
  //PORTA |= (1<<AD7708_CS); //CS high   
 
  //
  //    To write to the Communication Register to go to the Filter Register
  //
  //reg &= 0x03;
  //PORTA &= ~(1<<AD7708_CS); //CS low
  SPDR = 0x03 ;        //communications register
  while((SPSR&0x80)==0);
  //reg = SPDR ;
  SPDR = 0x03;
  while((SPSR&0x80)==0);
  //reg = SPDR;         
  //PORTA |= (1<<AD7708_CS); //CS high   
 





while (1)
      {
      // Place your code here

      };
}

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