microcontroller - ADC registers setup using spi communication

I'm new to microcontrollers - I'm trying to read external ADC values from an AD7798 ADC using SPI communication.

Initially I have to setup some ADC registers - some registers are not configured. To configure the registers, I have to use the communication register to select which register I want to configure.

For example, I want to set the AD7798 configuration register (16bit). I have code like this: #include #define ADC_CS PORTB.3 #define WG_CS PORTB.4 #define MOSI PORTB.5 #define MISO_PU PORTB.6 #define MISO_PIN PINB.6 #define SCK PORTB.7

//global functions.
unsigned int adcConfig;
unsigned int adcMode;
unsigned int adcId;


void init_io(void) 
{ 
DDRB = 0xBF;        // make SCK, MOSI, CS1, CS2 outputs 
ADC_CS = 1;              //disable ADC 
WG_CS = 1;               //disable WaveGenerator 
MISO_PU = 1;             //enable pull-up on MISO so we can test !RDY 
} 

unsigned char spi(unsigned char data) 
{ 

//Start transmision 
SPDR = data; 
//Wait for transmision complete 
while (!(SPSR & (1<return SPDR; 
} 

//Sets the waveform generator output to given phase 
void SetWGPhase(unsigned int phase) 
{ 

SPCR = 0x5A; // mode #2 F_CPU/64 
WG_CS = 0;                      // enable 
spi(0x20); 
spi(0x00); 
spi((phase >> 8) | 0xC0);       //Load into phase register 0 
spi(phase & 0x00FF); 
WG_CS = 1; 
} 

void setupAd(){ 

    SPCR = 0x5D; 
    ADC_CS = 0; 
   // while(spi(0x10) != 0x10); 
    spi(0x10);                  //set up communication register for configuration reg. 
    spi(0x07);        
    spi(0x10); 

    spi(0x08);                  //set up communication register for mode reg. 
    spi(0x00);        
    spi(0x0A); 

    ADC_CS = 1; 
    } 


 unsigned int ReadAd(void) 
 { 
unsigned int data; 
SPCR = 0x5D; // mode #3 F_CPU/16 
CheckStatus();
ADC_CS = 0;                     // enable 

while (MISO_PIN != 0) ;         // wait for  DOUT/!RDY line to go low 
//Read data 
spi(0x58);                      //Place readinstruction in communication register 
data = spi(0xFF);               // read hi-byte 
data = (data << 8) | spi(0xFF); // and lo-byte. 
ADC_CS = 1;                     // disable 
return data; 
} 

 unsigned char CheckStatus(void)

{
char adcStatus; 
            SPCR = 0x5D;
            ADC_CS = 0;                     // enable  
            while(ADC_CS_PIN);
            adcStatus = 0xFF; 
while(!(adcStatus & 0x80)){                                     

             spi(0x40);
             adcStatus = spi(0xFF); 

          }          
ADC_CS = 1;                      

return adcStatus;
}

unsigned int ReadAdConfReg(void) 
{              
  unsigned int retvalconfig;
SPCR = 0x5D;  

ADC_CS = 0;      
while (MISO_PIN != 0) ; 
spi(0x50); 
adcConfig = spi(0xFF);    
adcConfig = (adcConfig << 8) | spi(0xFF); 
retvalconfig= adcConfig;
ADC_CS = 1; 
return retvalconfig;
} 


unsigned int ReadAdModeReg(void) 
{              
  unsigned retvalmode;
SPCR = 0x5D;  
ADC_CS = 0;        
while (MISO_PIN != 0) ; 
spi(0x48); 
adcMode = spi(0xFF);  
adcMode = (adcMode << 8) | spi(0xFF); 
retvalmode =adcMode;   

ADC_CS = 1;
return retvalmode;
} 
unsigned int ReadAdIdReg(void) 
{              

SPCR = 0x5D;  
ADC_CS = 0;          
while (MISO_PIN != 0) ; 
spi(0x60); 

adcId = spi(0xFF);    
ADC_CS = 1;
 return adcId; 
} 

when I print configuration register it is giving value"16383". but when I power off/on the target i am getting "1808(which is equivalent to 0x0710)" after that it is giving same value as"16383". I have tested with different configurations also but it is not changing, always printing "16383" except power off/on.I think default value.

Even with mode register it is always printing"10(which is equivalent to 0x000A)" but that is the value i am getting always, even if I change the configuration to "0x0022".

Even I have tried to read Id register, but it is giving "0x48". but in data sheet it mentioned "0xX8" for AD7798. Thanks in advance.

Someone help me please, I am not getting any idea about what mistake I am doing here.