Compiler/MSP430G2553: LCD display internal temperature with some differences.

Tool/software: TI C/C++ Compiler

Hello,

I 'm using MSP430G2553 to display temperature using internal senzor.

The problem is he works fine, but sometimes the values displayed on the LCD have very large differences. For example it shows 28.5, 29.1, 29.5.... and after some minutes : 21 , 29, 18, 30 ...

The range between measurements is 2 seconds. I am using IAR IDE and in debug mode i saw in watch tool the value that is transmitted to the LCD display function looks very well, without big differences. So the problem has to be somewhere on the display function.

There is my code and thanks:

#include  <msp430g2553.h>

#define lcd_port    		P1OUT
#define lcd_port_dir 	P1DIR
 

#define LCD_EN     	BIT4 
#define LCD_RS      BIT5 
unsigned char b[4];
int i,j = 0;
int g;

unsigned int aa, bb,cc,dd,ee,ff,gg;

float ADCDATA;
float tempInDeg;
long tempInDeg1;




void lcd_reset()
{
	lcd_port_dir = 0xff;	// output mode
	lcd_port = 0xff;
	__delay_cycles(20000);
	lcd_port = 0x03+LCD_EN;
	lcd_port = 0x03;
	__delay_cycles(10000);
	lcd_port = 0x03+LCD_EN;
	lcd_port = 0x03;
	__delay_cycles(1000);
	lcd_port = 0x03+LCD_EN;
	lcd_port = 0x03;
	__delay_cycles(1000);
	lcd_port = 0x02+LCD_EN;
	lcd_port = 0x02;
	__delay_cycles(1000);
}
 
void lcd_cmd (char cmd)
{ 
	// Send upper nibble
	lcd_port = ((cmd >> 4) & 0x0F)|LCD_EN;
	lcd_port = ((cmd >> 4) & 0x0F);
 
	// Send lower nibble
	lcd_port = (cmd & 0x0F)|LCD_EN;
	lcd_port = (cmd & 0x0F);
 
	__delay_cycles(4000);
}

void lcd_init ()
{
	lcd_reset();         // Call LCD reset
	lcd_cmd(0x28);       // 4-bit mode - 2 line - 5x7 font. 
	lcd_cmd(0x0C);       // Display no cursor - no blink.
	lcd_cmd(0x06);       // Automatic Increment - No Display shift.
	lcd_cmd(0x80);       // Address DDRAM with 0 offset 80h.
	lcd_cmd(0x01);		 // Clear screen
}

 
void lcd_data (unsigned char dat)
{
	// Send upper nibble 
	lcd_port = (((dat >> 4) & 0x0F)|LCD_EN|LCD_RS);
	lcd_port = (((dat >> 4) & 0x0F)|LCD_RS);
	
	// Send lower nibble
	lcd_port = ((dat & 0x0F)|LCD_EN|LCD_RS);
	lcd_port = ((dat & 0x0F)|LCD_RS);
 
	//__delay_cycles(4000); // a small delay may result in missing char display
        __delay_cycles(2000);
}


void display_line(char *line)
{
	while (*line)
		lcd_data(*line++);
}

int main()
{
	// Stop Watch Dog Timer
	WDTCTL = WDTPW + WDTHOLD;


     ADC10CTL0 = ADC10SHT_3 + SREF_1  + REFON + ADC10ON;
    ADC10CTL1 = INCH_10 + ADC10DIV_3;

  

    __delay_cycles(30); 

        
	lcd_init();   // Initialize LCD
	
        while (1){
        
          
 /////temp
     
       ADC10CTL0 |= ENC + ADC10SC;            // Sampling and conversion start
       while (ADC10CTL1 & ADC10BUSY);          // check for ADC conversion is completed
 
       ADCDATA = ADC10MEM;                 // Read ADC value  
      
 tempInDeg1= 413*(long)ADCDATA-277746;///

 
bb =(tempInDeg1/10000)%10;   // f
cc =(tempInDeg1/1000)%10;      //
dd='.';                                             //
ee =(tempInDeg1/100)%10;        //
ff=0xF8;      //Symbol  for dg
gg='C';
 

	lcd_cmd(0x80); // select 1st line (0x80 + addr) - here addr = 0x00
	
display_line("T:");
        

//Transfer to LCD , example: 28.5
  lcd_data(bb + 48);      
  lcd_data(cc + 48);
  display_line(".");
  lcd_data(ee + 48);
     
 
lcd_cmd(0xc0); // select 2nd line (0x80 + addr) - here addr = 0x40
  
  __delay_cycles(2000000);
      
}
}