SHT75 Codeproblem

So haben uns jetz an den Code von sensirion gehalten mit allen zeiten
usw.
Es geht immernoch nix. Selbst wenn wir eine slave adresse angeben die es
nicht gibt meldet er erfolgreich gesendet.
Kann bitte jemand nochmal drüberschauen.
Is es eigentlich egal an welche Pins man den Sensor anschließt? Wir 
haben ihn jetz an den Pins PC1 und PC0 vom ATmega16.
Danke

void S_SDA() {
DDRC  |= (1<<SDA);
PORTC |= (1<<SDA);
}

void C_SDA(){
DDRC  |= (1<<SDA);
PORTC &= ~(1<<SDA);
}

void S_SCL(){
DDRC  |= (1<<SCL);
PORTC |= (1<<SCL);
}

void C_SCL(){
DDRC  |= (1<<SCL);
PORTC &= ~(1<<SCL);
}

unsigned char G_SDA(){
DDRC &= ~(1<<SDA);
if ((PORTC & (1 << SDA)) == 1) { return 1;} else  { return 0;};
}

void SHT7Start(void) {
S_SDA();
C_SCL();
delay_us(5);
S_SCL();
delay_us(5);
C_SDA();
delay_us(5);
C_SCL();
delay_us(5);
S_SCL();
delay_us(5);
S_SDA();
delay_us(5);
C_SCL();
}


void SHT7Reset(void) {

}

unsigned char SHT7Read(unsigned char SHTACK) {
unsigned char i, tempvalue=0;
S_SDA();                           //release DATA-line
  for (i=0x80;i>0;i/=2)             //shift bit for masking
  { S_SCL();                          //clk for SENSI-BUS
    if (G_SDA == 1) {tempvalue = (tempvalue | i);};        //read bit
    delay_ms(10);
    C_SCL();
    delay_ms(100);
  }
  if (SHTACK == 0){S_SDA();}
  else {C_SDA();};               //in case of "ack==1" pull down 
DATA-Line
  S_SCL();                            //clk #9 for ack
  delay_us(5);                            //pulswith approx. 5 us
  C_SCL();
  delay_us(5);
  S_SDA();                           //release DATA-line
  return tempvalue;
}




char SHT7Write(unsigned char Data) {
unsigned char i,error=0;
  for (i=0x80;i>0;i/=2)               //shift bit for masking
  { if ((i & Data) == i) {S_SDA();}  //masking value with i , write to 
Bus
    else {S_SDA();};
    S_SCL();                          //clk for SENSI-BUS
    delay_us(5);                        //pulswith approx. 5 us
    C_SCL();
    delay_ms(100);
  }
  S_SDA();                           //release DATA-line
  S_SCL();                            //clk #9 for ack

  error=G_SDA();           //check ack (DATA will be pulled  down by 
SHT11)

  C_SCL();
  return error;                     //error=1 in case of no acknowledge
}