DS1621 interface with PIC18F4520 using C18 compiler

[Jayant Gupta]

hi

i m working on a project where i need to get the temperature using DS1621 via I2C protocol and display the temperature on LCD.

as per the updats i have written the I2C protocol & LCD program.

the question remains the data that i have got from I2C is not being displayed on to the LCD.i.e.the tempHI and tempLO values are not being displayed.

 

here is my code so far.

 

#include<p18f4520.h>
#include<i2c.h>
#include<delays.h>

#define _XTAL_FREQ 4e6 // 4MHz
#define LCD_DATA PORTD
#define LCD_RS PORTBbits.RB0 //register select
#define LCD_RW PORTBbits.RB1  //write on lcd
#define LCD_EN PORTBbits.RB2  //enable on lcd

void lcdstrobe(void) // Generate the E pulse
{
    LCD_EN=0; // E = 0
    Delay1KTCYx(100); // 10ms delay for LCD_EN to settle
    LCD_EN=1; // E = 1
}

void lcd_write_cmd(unsigned char cmd)
{
    LCD_RS=0;
    LCD_RW=0;
    PORTD=cmd;    
    lcdstrobe();
}

void lcd_write_data(char data)
{
    LCD_RS=1; // Select LCD for data mode
    LCD_RW=0;
    PORTD =(data);
    lcdstrobe();
}

void init_lcd(void)
{
    lcd_write_cmd(0x38);
    lcd_write_cmd(0x06);
    lcd_write_cmd(0x0C);
    lcd_write_cmd(0x01);
}

/*//***********************hex2bcd******************** ***
unsigned char hex2bcd(unsigned char data)
{
unsigned char msb,lsb;
msb = data/10;
msb = msb << 4;
lsb = data % 10;
data = msb|lsb;
return data;
}*/

void main()
{
    char tempHI=0;
    char tempLO=0;
    char MSB1=0;
    char LSB1=0;

    TRISC=0x00; // turn on tri-state register and make all output pins
    PORTC=0x00; // output pins are LOW

    TRISD=0x00;
    TRISB=0x00;
    LCD_EN=1;
    init_lcd();
    while(1)
    {
        LCD_RS = 1;
        LCD_EN=1;
        Delay1KTCYx(1);
// ============== CALL THE DATA FROM I2C SENSOR =================
//**********************************I2C COMMUNICATION***********************************
        OpenI2C(MASTER, SLEW_OFF);
        SSPADD=0x27; // communication @ 100KHz for 4MHz
    
        StartI2C(); //begin I2C
        IdleI2C();
        WriteI2C(0x90); //send address to the device

        IdleI2C();
        WriteI2C(0xAC); // sends a control byte to the device to acces the configuration register
    
        IdleI2C();
        WriteI2C(0x02);  // sends configuration byte for continuous conversion and active high polarity

        IdleI2C();
        RestartI2C();     // briefly restart I2C communications
        IdleI2C();
        WriteI2C( 0x90 ); // again sending the address to the device
    
        IdleI2C();
        WriteI2C(0xEE); //command for temperature conversion
        IdleI2C();
        StopI2C(); //stop I2C communication

        StartI2C(); //start I2C communication
        IdleI2C();
        WriteI2C(0x90); //Send the address to the device
        IdleI2C();
        WriteI2C(0xAA); //access the temperature register
        IdleI2C();
        RestartI2C(); //initiate restart command
        IdleI2C();
        WriteI2C(0x91); // read from the register
        IdleI2C();
        tempHI=ReadI2C(); //MSB in tempHI

        IdleI2C();
        AckI2C(); // send acknowledge
        IdleI2C();
        tempLO=ReadI2C(); //LSB in tempLO

        IdleI2C();
        NotAckI2C(); // send not acknowledge
        IdleI2C();
        StopI2C(); // Stop all I2C communication
       
//********************************** LCD DISPLAY OF TEMPERATURE ***********************************
        lcd_write_cmd(0x80); // Move cursor to line 1 position 1
 
        lcd_write_data(‘T’);
        lcd_write_data(‘E’);
        lcd_write_data(‘M’);
        lcd_write_data(‘P’);
        lcd_write_data(‘:’);

         lcd_write_data(48);        // Display the temperature
        lcd_write_data(0xDF);
        lcd_write_data(‘C’);
       
    }
}

 

 

thanks

[AJISH ALFRED]

I can see that you will get output like the following only;

TEMP:0#C

Is it??

Because from the main function you are only calling the following functions related to lcd

        lcd_write_data(‘T’);
        lcd_write_data(‘E’);
        lcd_write_data(‘M’);
        lcd_write_data(‘P’);
        lcd_write_data(‘:’);

         lcd_write_data(48);        // Display the temperature
        lcd_write_data(0xDF);
        lcd_write_data(‘C’);

 

You are not accessing the temperature data which you’ve stored in the register using i2c communication.

[Jayant Gupta]

yes my abjective is to see the output on the lcd as

 

TEMP:#degreeC

# gives the output from the DS1621 sensor.

 

i have some how manage to work on the I2C protocol but i m not sure is it right or wrong since lcd interfacing in not yet successful

 

secondly i have tried the lcd part too but i am not able append it properly in te code. i am confused with the delays that i am giving.

even though i refered to previous suggestion but i m not able to successful in the program.

 

i haven’t figured a way to call the value in  tempHI  register onto the lcd and finding it quite hard to understanding any other method of projecting the data.

[Author]

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