[SOLVED] How to compare the two temperatures from lm35 to pic18f4550?

[vgavale]

can read the values of two lm35 also can display. but how to compare both temperature?
i want to compare values t1 and t2.plz help.


[c code]

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Code C - [expand]
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/*
LCD DATA port----PORT B
signal port------PORT D
    rs-------RE0
    rw-------RE1
    en-------RE2
*/
#include <p18f4550.h>
#include<math.h>
#include<stdlib.h>
#include<stdio.h>
#include<ctype.h>
 
//LCD data pins connected to PORTD and control pins connected to PORTE
#define LCD_DATA    PORTB               //LCD data port
#define ctrl        PORTD              //LCD signal port
#define en          PORTDbits.RD7      // enable signal
#define rw          PORTDbits.RD6      // read/write signal
#define rs          PORTDbits.RD5     // register select signal
#define Channel0 0b00000000
#define Channel1 0b00000100
 
void ADC_Init();
void Select_Channel(unsigned char Channel);
unsigned int Get_ADC_Result(void);
void Start_Conversion(void);
 
void myMsDelay (unsigned int time);
 
//LCD function definitions
void LCD_Busy(void);
void LCD_cmd(unsigned char cmd);
void init_LCD(void);
void LCD_write(unsigned char data);
void LCD_write_string(static char *str);
 
/*The following lines of code perform interrupt vector relocation to work with the USB bootloader. These must be
used with every application program to run as a USB application.*/
extern void _startup (void);
#pragma code _RESET_INTERRUPT_VECTOR = 0x1000
 
void _reset (void)
{
        _asm goto _startup _endasm
}
 
#pragma code
#pragma code _HIGH_INTERRUPT_VECTOR = 0x1008
void high_ISR (void)
{
}
 
#pragma code
#pragma code _LOW_INTERRUPT_VECTOR = 0x1018
void low_ISR (void)
{
}
#pragma code
//Function to generate delay
void myMsDelay (unsigned int time)
{
        unsigned int i, j;
        for (i = 0; i < time; i++)
                for (j = 0; j < 710; j++);/*Calibrated for a 1 ms delay in MPLAB*/
}
 
 
// Function to initialise the LCD
void init_LCD(void)
{
    LCD_cmd(0x38);      // initialization of 16X2 LCD in 8bit mode
    myMsDelay(15);
 
    LCD_cmd(0x01);      // clear LCD
    myMsDelay(15);
 
    LCD_cmd(0x0C);      // cursor off
    myMsDelay(15);
 
    LCD_cmd(0x80);      // ---8 go to first line and --0 is for 0th position
    myMsDelay(15);
 
            // ---8 go to first line and --0 is for 0th position
 
    return;
}
//Function to pass command to the LCD
void LCD_cmd(unsigned char cmd)
{
    LCD_DATA = cmd;
    rs = 0;
    rw = 0;
    en = 1;
    myMsDelay(15);
    en = 0;
    myMsDelay(15);
    return;
}
 
//Function to write data to the LCD
void LCD_write(unsigned char data)
{
    LCD_DATA = data;
    rs = 1;
    rw = 0;
    en = 1;
    myMsDelay(5);
    en = 0;
    myMsDelay(5);
    return ;
}
//Function to split the string into individual characters and call the LCD_write function
void LCD_write_string(static char *str)   //store address value of the string in pointer *str
{
    int i = 0;
    while (str[i] != 0)
    {
        LCD_write(str[i]);      // sending data on LCD byte by byte
        myMsDelay(15);
                i++;
    }
    return;
}
 
void ADC_Init()
{
 ADCON0=0b00000000; //A/D Module is OFF no channel selected
 ADCON1=0b00001110; // Reference as VDD & VSS, AN0 set as analog pins
 ADCON2=0b10001110; // Result is right Justified
                    //Acquisition Time 2TAD
                    //ADC Clk FOSC/64
 ADCON0bits.ADON=1; //Turn ON ADC module
}
 
void Select_Channel(unsigned char Channel)
{
 ADCON0=ADCON0 & 0b11000001;    
 ADCON0=ADCON0 | Channel;   //selecting channel no 0
}
 
void Start_Conversion()
{
 ADCON0bits.GO=1;
}
 
 
//If you do not wish to use adc conversion interrupt you can use this
//to do conversion manually. It assumes conversion format is right adjusted
unsigned int Get_ADC_Result()
{
 
 unsigned int ADC_Result=0;
 while(ADCON0bits.GO);
 ADC_Result=ADRESL;
 ADC_Result|=((unsigned int)ADRESH) << 8;
return ADC_Result;
 
}
 
 void main(void)
{
//unsigned int adc_val;
unsigned int a;
unsigned char i=0;
unsigned char pot0[6],pot1[6];
unsigned float val,val1;
unsigned double t2,t1,x1,x2;
//char buffer[20];
 
   char var1[] = "LM35 test";
     ADCON1 = 0x0F;        //Configuring the PORTE pins as digital I/O 
     TRISB = 0x00;         //Configuring PORTD as output
     TRISD = 0x00;         //Configuring PORTE as output  
     TRISAbits.TRISA0=1;        //RA0=Input for analog input
    TRISDbits.TRISD3=0; //ULN ON
     TRISDbits.TRISD4=0;    //Buzzer set
        
     
    
     init_LCD();           // initialization of LCD
     myMsDelay(50);       // delay of 50 mili seconds
      ADC_Init();
     LCD_write_string(var1);
while(1)
{
 
Select_Channel(Channel0);
Start_Conversion();
 
val= Get_ADC_Result();
 
t1=(double) val*50/1023*1000;   //atm temp
     x1=(double)t1/100;
//unsigned float  x;
 
  itoa(x1,pot0);
  //LCD_cmd(0xC0); // Move cursor to line 2 position 1
  // LCD_cmd(0x8c);
 for(i=0;pot0[i]!='\0';i++)
{
     LCD_write (pot0[i]);
}
  myMsDelay(1);
 
 
 
** * *// LCD_write(val); * * * * *// Display the temperature*
* * * //*LCD_write(0xDF);
* * * * //LCD_write('C');
 
Select_Channel(Channel1);
Start_Conversion();
val1= Get_ADC_Result();
t2=(double) val1*50/1023*1000;
     x2=(double)t2/100;
itoa(x2,pot0);
 
 // LCD_cmd(0x8c);
  for(i=0;pot1[i]!='\0';i++)
{
     LCD_write (pot1[i]);
}
  myMsDelay(100);
 
 
 
** * *// LCD_write(val); * * * * *// Display the temperature*
* * * //*LCD_write(0xDF);
* * * * //LCD_write('C');
//}
 
//while(1)
//{
 
LCD_cmd(0xC0); // Move cursor to line 2 position 1
/*if(t1<15)
//{
  w hile(t2!=80)*/
while((t1<15) && (t2 != 80))  
{
     for(i=0;pot0[i]!='\0';i++)
    {
     LCD_write (pot0[i]);
    }
 myMsDelay(100);
 
}
  *
* * *LCD_write(0xDF);
* * LCD_write('C');
 
  myMsDelay(1);
   
    PORTDbits.RD3=0;
     PORTDbits.RD4=1;
 
 
 /*else if(15<t1<25)
{
  while(t2!=60)*/
while((15<t1<25) && (t2 !=60))
{
     for(i=0;pot0[i]!='\0';i++)
    {
     LCD_write (pot0[i]);
    }
}
LCD_write(0xDF);
* * LCD_write('C');
  myMsDelay(1);
   
    PORTDbits.RD3=0;
     PORTDbits.RD4=1;
 
 
}
/*else
{
 
  while(t2!=40)*/
while((t1>25) && (t2!=40))
{
     for(i=0;pot0[i]!='\0';i++)
    {
     LCD_write (pot0[i]);
    }
}
    LCD_write(0xDF);
* * LCD_write('C');
    myMsDelay(1);
    PORTDbits.RD3=0;
    PORTDbits.RD4=1;
 
}
}
}

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[paulfjujo]

hello


Compare to what ?
some threshold values ?
compare each other, wich is superior as the other ?
explain more ..


you better have to use raw value (ADC result) for comparaison
so between integer value..if scaling in physical unit (°C) are the same for both sensors