Atmega32

[s.manisrinivas]

i am using lm75 b temperature sensor interface to atmega32 controller .my problem is i sending the address to read i.e. 10010001 (0x91) but the value is displaying in lcd display .

iam using pull up resistors – 10k 

cpu freq -16mhz

code is below

 

this is main file

 

 

#define F_CPU 16000000UL    //this must be first line 

 

#include <avr/io.h>

#include "i2c.h"

#include "LCDa.h"

#include <util/delay.h>

#include <stdlib.h>

 

 

 

unsigned int read_temperature(unsigned char LM75_addr);

 

unsigned int temperature;

 char buffer[14];

 

unsigned int read_temperature(unsigned char LM75_addr) //function for reading temperature

{

 

unsigned int temp;

 

I2C_Start(); // start i2c

 

I2C_Write(0x90);// write address

I2C_Start();

// I2C_Write(0x01);

_delay_ms(1);

I2C_Write(0x00);

//I2C_Stop();

_delay_ms(1);

 

I2C_Write(LM75_addr);

 

 

temp=I2C_Read_ACK(); //get high byte

temp<<=8;

temp|=I2C_Read_NACK(); // get low byte

temp>>=5;

I2C_Stop();

 

return temp; //return temperature coded in second complement

}

 

 

 

 

 

int main()

{

     

 

 _delay_ms(100);

 

    lcd_init();

Init_I2C();

lcd_display_on_off(1,1,1);

 

 

while(1)

{

lcd_clear_display();

    temperature = read_temperature(0x91);//0x90+1

    itoa(temperature,buffer,10); 

lcd_gotoxy(0,0);

lcd_puts("temp is:");

    lcd_gotoxy(0,1);

lcd_puts(buffer);

_delay_ms(200);

}

   

   

}

 

this is i2c routines

 

 

 

#include <avr/io.h>

#include "i2c.h"

 

 

unsigned char I2C_Read_NACK(void)

{

TWCR = (1<<TWINT)|(1<<TWEN);

while ((TWCR & (1<<TWINT)) == 0);

return TWDR;

}

void Init_I2C()

{

#define SCL_presceler 1

TWSR=0;  //no presceler

TWBR=0x20; //  ((F_CPU/F_SCL)-16)/2 -> F_SCL=cca 10000Hz

TWCR = (1<<TWEN);

}

unsigned char I2C_get_status(void)

{

unsigned char  status;

status = TWSR & 0xF8;

return status;

}

void I2C_Start()

{

TWCR = (1<<TWINT)|(1<<TWSTA)|(1<<TWEN);

while ((TWCR & (1<<TWINT)) == 0 );

 

}

void I2C_Stop()

{

TWCR = (1<<TWINT)|(1<<TWSTO)|(1<<TWEN);

}

void I2C_Write(unsigned char data)

{

TWDR = data;

TWCR = (1<<TWINT)|(1<<TWEN);

while ((TWCR & (1<<TWINT)) == 0);

}

 

unsigned char I2C_Read_ACK(void)

{

TWCR = (1<<TWINT)|(1<<TWEA)|(1<<TWEN);

while ((TWCR & (1<<TWINT)) == 0);

return TWDR;

}

 

 

[Faroogh]

Lm35 is not 12c device use ADC to read the signal and apply formulas to the adc read value then print it to Lcd

[Saatwik]

you can get idea from this to get input from sensor just connect the sensor at place of potentiometer. https://www.engineersgarage.com/embedded/avr-microcontroller-projects/adc-circuit

[Author]

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