problem in atmega32 interfacing with sht75

#include <stdint.h>
#include <stdio.h>
#include <avr/io.h>
#include <util/delay.h>
#include "global.h"
#include "rprintf.h"
#include "timer.h"
//#include "lcd.h"
#include "uart.h"
#include "math.h"


//typedef union
//{ 
//unsigned int i;
//float f;
//} value;
//----------------------------------------------------------------------------------
// modul-var
//----------------------------------------------------------------------------------
enum {TEMP,HUMI};
#define SHT_DDR			DDRC		// Port with clock and data pins
#define SHT_PORT		PORTC		// Port with clock and data pins
#define SHT_PIN			PINC		// Port with clock and data pins
#define SHT_CLOCK		7		// Pin used to output clock to SHT
#define SHT_DATA		6		// Pin used to read/output data from/to SHT
#define SHT_DELAY		25		// uS delay between clock rise/fall



//adr command r/w
#define STATUS_REG_W 0x06 //000 0011 0
#define STATUS_REG_R 0x07 //000 0011 1
#define MEASURE_TEMP 0x03 //000 0001 1
#define MEASURE_HUMI 0x05 //000 0010 1
#define RESET 0x1e //000 1111 0

#define noACK   0
#define ACK     1

void enable_data(void) 	{ SHT_DDR |= (1 << SHT_DATA); }	// Drive DATA pin

// Set the DDR Register to 0 (low) and the PORT Register to 1 (high)
// Result: PIN is ready for Input with Pull-UP

void disable_data(void)	{ SHT_DDR  &= ~(1 << SHT_DATA);
			  SHT_PORT |= (1 << SHT_DATA); }

// Set DATA PORT Register to 1 (high)

void data_high(void)	{ SHT_PORT |= _BV(SHT_DATA); }

// Set DATA PORT Register to 0 (low)

void data_low(void)	{ SHT_PORT &= ~_BV(SHT_DATA); }

// Set CLOCK PORT Register to 1 (high)

void clock_high(void)	{ SHT_PORT |= _BV(SHT_CLOCK); }

// Set CLOCK PORT Register to 0 (low)

void clock_low(void)	{ SHT_PORT &= ~_BV(SHT_CLOCK); }

// Set CLOCK DDR Register to 1 (high)

void enable_clock(void)	{ SHT_DDR |= (1 << SHT_CLOCK); }






//----------------------------------------------------------------------------------
char s_write_byte(unsigned char value)
//----------------------------------------------------------------------------------
// writes a byte on the Sensibus and checks the acknowledge
{
     unsigned char i;
	unsigned char error = 0;

	// Set the DATA Line to Output

	enable_data();
	asm volatile ("nop"::);

	// Write each bit one at a time, LSB first

	for (i=0x80;i>0;i/=2)
	{
		if (i & value)
		{
			data_high(); // Write a 1
		}
		else
		{
			data_low();  // Write a 0
		}

		clock_high();
		asm volatile ("nop"::);
		asm volatile ("nop"::);
		clock_low();
		asm volatile ("nop"::);
		asm volatile ("nop"::);

	}
	disable_data();
	asm volatile ("nop"::);

	// Read ACK

	clock_high();
	asm volatile ("nop"::);
	asm volatile ("nop"::);

	error = bit_is_set(SHT_PIN, SHT_DATA);

	clock_low();

	return error; //error=1 in case of no acknowledge
}
//----------------------------------------------------------------------------------
char s_read_byte(unsigned char ack)
//----------------------------------------------------------------------------------
// reads a byte form the Sensibus and gives an acknowledge in case of "ack=1"
{
unsigned char i,val=0;

	// Set the DATA Line to Input. 
	// Important: If there is no external Pull-Up Resistor

	disable_data();
	asm volatile ("nop"::);

	// Read in 8 bits, LSB first

	for (i=0x80;i>0;i/=2)
	{
		clock_high();
		asm volatile ("nop"::);
		asm volatile ("nop"::);

		if (bit_is_set(SHT_PIN, SHT_DATA))
		{
			val=(val | i); // Got a Bit
		}
		clock_low();
		asm volatile ("nop"::);
		asm volatile ("nop"::);
	}

	// Send ACK
	enable_data();
	asm volatile ("nop"::);
	data_low();
	asm volatile ("nop"::);
	clock_high();
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	clock_low();
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	disable_data();

	return val;

}
//----------------------------------------------------------------------------------
void s_transstart(void)
//----------------------------------------------------------------------------------
// generates a transmission start
// _____ ________
// DATA: |_______|
// ___ ___
// SCK : ___| |___| |______
{
enable_data();
	asm volatile ("nop"::);
	data_high();
	clock_low();
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	clock_high(); 
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	data_low();
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	clock_low();
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	clock_high();
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	data_high();
	asm volatile ("nop"::);
	asm volatile ("nop"::);
	clock_low();

}
//----------------------------------------------------------------------------------
void s_connectionreset(void)
//----------------------------------------------------------------------------------
// communication reset: DATA-line=1 and at least 9 SCK cycles followed by transstart
// _____________________________________________________ ________
// DATA: |_______|
// _ _ _ _ _ _ _ _ _ ___ ___
// SCK : __| |__| |__| |__| |__| |__| |__| |__| |__| |______| |___| |______
{
unsigned char i;

	// Set DATA Line to Input

	enable_data();
	asm volatile ("nop"::);
	data_high();

	// Prepare CLOCK-Line for Pulses

	clock_low();
	
	// Send 9 Pulses on the CLOCK-Line

	for(i=0;i<10;i++)
	{
		clock_high();
		asm volatile ("nop"::);
		asm volatile ("nop"::);
		clock_low();
		asm volatile ("nop"::);
		asm volatile ("nop"::);
	}
	s_transstart();//transmission start

}
//----------------------------------------------------------------------------------
char s_softreset(void)
//----------------------------------------------------------------------------------
// resets the sensor by a softreset
{
unsigned char error=0;
s_connectionreset(); //reset communication
error+=s_write_byte(RESET); //send RESET-command to sensor
return error; //error=1 in case of no response form the sensor
}
//----------------------------------------------------------------------------------
char s_read_statusreg(unsigned char *p_value, unsigned char *p_checksum)
//----------------------------------------------------------------------------------
// reads the status register with checksum (8-bit)
{
unsigned char error=0;
s_transstart(); //transmission start
error=s_write_byte(STATUS_REG_R); //send command to sensor
*p_value=s_read_byte(ACK); //read status register (8-bit)
*p_checksum=s_read_byte(noACK); //read checksum (8-bit)
return error; //error=1 in case of no response form the sensor
}
//----------------------------------------------------------------------------------
char s_write_statusreg(unsigned char *p_value)
//----------------------------------------------------------------------------------
// writes the status register with checksum (8-bit)
{
unsigned char error=0;
s_transstart(); //transmission start
error+=s_write_byte(STATUS_REG_W);//send command to sensor
error+=s_write_byte(*p_value); //send value of status register
return error; //error>=1 in case of no response form the sensor
}
//----------------------------------------------------------------------------------
char s_measure(unsigned char *p_value, unsigned char *p_checksum, unsigned char
mode)
//----------------------------------------------------------------------------------
// makes a measurement (humidity/temperature) with checksum
{
unsigned char error=0;
unsigned int i;
s_transstart(); //transmission start
switch(mode){ //send command to sensor
case TEMP : error+=s_write_byte(MEASURE_TEMP); break;
case HUMI : error+=s_write_byte(MEASURE_HUMI); break;
default : break;
}
for (i=0;i<65535;i++)
{ 
if (! bit_is_set(SHT_PIN, SHT_DATA))
		{
			break;
		}
		_delay_ms(300);
//
}
if (! bit_is_set(SHT_PIN, SHT_DATA))
 error+=1; // or timeout (~2 sec.) is reached
*(p_value) =s_read_byte(ACK); //read the first byte (MSB)
*(p_value+1)=s_read_byte(ACK); //read the second byte (LSB)
*p_checksum =s_read_byte(noACK); //read checksum
return error;
}
//----------------------------------------------------------------------------------
void calc_sth11(float *p_humidity ,float *p_temperature)
//----------------------------------------------------------------------------------
// calculates temperature [°C] and humidity [%RH]
// input : humi [Ticks] (12 bit)
// temp [Ticks] (14 bit)
// output: humi [%RH]
// temp [°C]
{ 
const float C1= -2.0468; // for 12 Bit RH
const float C2= +0.0367; // for 12 Bit RH
const float C3= -0.0000015955; // for 12 Bit RH
const float T1= +0.01; // for 12 Bit RH
const float T2= +0.00008; // for 12 Bit RH

float rh=*p_humidity; // rh: Humidity [Ticks] 12 Bit
float t=*p_temperature; // t: Temperature [Ticks] 14 Bit
float rh_lin; // rh_lin: Humidity linear
float rh_true; // rh_true: Temperature compensated humidity
float t_C; // t_C : Temperature [°C]

t_C= ((t*0.01) - 40.1); //calc. temperature[°C]from 14 bit temp.ticks @5V
rh_lin =((C3*rh*rh)+(C2*rh)+C1); //calc. humidity from ticks to [%RH]
rh_true=((t_C-25)*(T1+T2*rh)+rh_lin); //calc. temperature compensated humidity [%RH]
if(rh_true>100)rh_true=100; //cut if the value is outside of
if(rh_true<0.1)rh_true=0.1; //the physical possible range
*p_temperature=t_C; //return temperature [°C]
*p_humidity=rh_true; //return humidity[%RH]
}
//--------------------------------------------------------------------
float calc_dewpoint(float h,float t)
//--------------------------------------------------------------------
// calculates dew point
// input: humidity [%RH], temperature [°C]
// output: dew point [°C]
{ 
float k,dew_point ;
k = (log10(h)-2)/0.4343 + (17.62*t)/(243.12+t);
dew_point = 243.12*k/(17.62-k);
return dew_point;
}
//----------------------------------------------------------------------------------
int main(void)
//----------------------------------------------------------------------------------
// sample program that shows how to use SHT11 functions
// 1. connection reset
// 2. measure humidity [ticks](12 bit) and temperature [ticks](14 bit)
// 3. calculate humidity [%RH] and temperature [°C]
// 4. calculate dew point [°C]
// 5. print temperature, humidity, dew point
{ 
//value humi_val,temp_val;
// initialize our libraries
	// initialize the UART (serial port)
	uartInit();
	// set the baud rate of the UART for our debug/reporting output
	uartSetBaudRate(9600);
	// initialize the timer system
	timerInit();

	// initialize rprintf system
	// - use uartSendByte as the output for all rprintf statements
	//   this will cause all rprintf library functions to direct their
	//   output to the uart
	// - rprintf can be made to output to any device which takes characters.
	//   You must write a function which takes an unsigned char as an argument
	//   and then pass this to rprintfInit like this: rprintfInit(YOUR_FUNCTION);
	rprintfInit(uartSendByte);

	// initialize vt100 library
	vt100Init();
	
	// clear the terminal screen
	vt100ClearScreen();
float humi_val,temp_val;
float dew_point;
unsigned char error,checksum;
unsigned int i;

//DDRC=0xFF; 
//DDRA=0xFF; 
//DDRB=0x07; 
//DDRD=0x00;
//PORTC=0x00; 

//sht init
enable_clock();	
clock_low();	
disable_data();


s_connectionreset();

while(1)
{ 
error=0;
//error+=s_read_statusreg((unsigned char *)&die_val.i);
error+=s_measure((unsigned char*) &humi_val,&checksum,HUMI); //measure humidity
error+=s_measure((unsigned char*) &temp_val,&checksum,TEMP); //measure temperature
if(error!=0) s_connectionreset(); //in case of an error: connection reset
else
{ 
//humi_val.f=(float)humi_val.i; //converts integer to float
//temp_val.f=(float)temp_val.i; //converts integer to float
//rprintfFloat(6,myflt2);

calc_sth11(&humi_val,&temp_val); //calculate humidity,temperature
dew_point=calc_dewpoint(humi_val,temp_val); //calculate dew point
//printf("temp:%5.1fC humi:%5.1f%% dew point:%5.1fC\n",temp_val.f,humi_val.f,dew_point);
//printf("id %5",die_val.i);
rprintfFloat(3,temp_val);
rprintf("\n");
rprintfFloat(3,humi_val);
rprintf("\n");
}
for (i=0;i<40000;i++); //(be sure that the compiler doesn't eliminate this line!)
}
return 0;
}