DS18b20 programming under Atmega8, serial communication computer display

MCU:Atmega8

Internal oscillator: 8M

Environment: ICCAVR 7.0

Program: sdyzxue Xue Haitao

2010/06/16

=*******************************************************
#include
#include
#define fosc 8000000
#define baud 9600
#define SEI() asm("sei")
#define CLR_DIR_1WIRE DDRC&=~BIT(1)     //Just modify the parameters here! Haha!
#define SET_DIR_1WIRE DDRC|=BIT(1)      //No need to modify anything inside!
#define CLR_OP_1WIRE PORTC&=~BIT(1)
#define SET_OP_1WIRE PORTC|=BIT(1)       
#define CHECK_IP_1WIRE (PINC & 0x02)    //Check
unsigned char wmh,wmm,wml;
unsigned int  temp,temp0,temp1,temp2;

unsigned char RX_data[10]={0};      //Data received by the serial port
unsigned char RX_counter=0;        //Counter of bytes received by the serial port

void delay_1us(void)                 //1us delay function
 {
  asm("nop");
 }

void delay_nus(unsigned int n)       //N us延时函数
  {
   unsigned int i=0;
   for (i=0;i    delay_1us();
  }
 
void delay_1ms(void)                 //1ms延时函数
  {
   unsigned int i;
   for (i=0;i<1140;i++);
  }
 
void delay_nms(unsigned int n)       //N ms延时函数
  {
   unsigned int i=0;
   for (i=0;i    delay_1ms();
  }
 
void putchar(unsigned char c)
{
   while (!(UCSRA&(1<    UDR=c;
}

//Character input function
unsigned char getchar(void)
{
   //Wait for receiving character
   while(!(UCSRA&(1<    return UDR;
}

//String output function
int puts(char *s)
{
   while (*s)
   {
        putchar(*s);
        s++;
    }
    return 1;
}

//String output function with carriage return and line feed
void puts_hh(char *s)
{
   while (*s)
   {
         putchar(*s);
        s++;
    }
//      putchar(0x0a); //line feedputchar 
     (0x0d);  //carriage return

}

//UART initialization
void uart_init(void)
{

UCSRB=(1<          //Enable sending and receiving  (RXCIE) and respond to the receive completion interrupt
     UBRRL=(fosc/16/baud+1)%256;
     UBRRH=(fosc/16/baud+1)/256;
     UCSRC=(1<         //8-bit data+1-bit stop bit
}

#pragma interrupt_handler UART_rx: iv_USART_RX
void UART_rx(void)                   //Serial port receive interrupt function
{           RX_data[RX_counter] = UDR;
          
          if (RX_data[RX_counter]=='t')
            {
               RX_data[0]=RX_data[RX_counter];
               RX_counter=0;
            }
          
          RX_counter++;                   //Count the number of bytes received
       
}
void init_1820() 
{ 
   SET_DIR_1WIRE;                //Set PC2 as output
   SET_OP_1WIRE;   
   CLR_OP_1WIRE; 
   delay_nus(480);    //More than 480us 
   SET_OP_1WIRE; 
   CLR_DIR_1WIRE; 
   delay_nus(20);     //15~60us 
   while(CHECK_IP_1WIRE); 
   SET_DIR_1WIRE; 
   SET_OP_1WIRE; 
   delay_nus(140);   //60~240us 
} 
void write_1820(unsigned char x) 
{     
    unsigned char m; 
   for(m=0;m<8;m++) 
   { 
      CLR_OP_1WIRE; 
      if(x&(1<  //Write data, write the low bit first!
      SET_OP_1WIRE; 
      else 
      {CLR_OP_1WIRE;} 
      delay_nus(40);   //15~60us 
      SET_OP_1WIRE; 
   } 
    SET_OP_1WIRE; 
} 
unsigned char read_1820() 
{      
   unsigned char temp,k,n; 
   temp=0; 
   for(n=0;n<8;n++) 
      { 
     CLR_OP_1WIRE; 
     SET_OP_1WIRE; 
     CLR_DIR_1WIRE; 
     k=(CHECK_IP_1WIRE);    //Read data, start from the low bit 
     if(k) 
     temp|=(1<
     else 
     temp&=~(1<
     delay_nus(50); //60~120us      
     SET_DIR_1WIRE; 
  } 
  return (temp); 
}

void gettemp()                   //Read temperature value
{   
    unsigned char temh,teml; 
    init_1820();        //Reset 18b20 
    write_1820(0xcc);   //Issue conversion command 
    write_1820(0x44);
    init_1820(); 
    write_1820(0xcc);  //Issue read command 
    write_1820(0xbe); 
    teml=read_1820();  //Read data 
    temh=read_1820();
 temp0=teml&0x0F;             //Decimal place
    temp1=(temh<<4)|(teml>>4);  //Integer place
    temp2=(temh>>3)&0x1F;        //Positive and negative temperature
    wmh=temp1/100;        //Above one hundred, output hundreds word
    wmm=(temp1%100)/10;   //Export parameters! wmh is the high tens digit displayed, wml is the low ones digit displayed
    wml=(temp1%100)%10;
    temp=temp0*625;        //decimal value
}

void main(void) //main function
{
 OSCCAL=0xb7; //system clock calibration, different chips and different frequencies,
   DDRC=0XFF;
   PORTC=0X00;
 uart_init();
 while(1)
  {          gettemp();

puts_hh("=====Temp Test=====");
   if(temp2)//Negative temperature
              {
             
              putchar('-');
               
              }
           if(!temp2)//Positive temperature
             {
             
              putchar('+');
               
             }

putchar(wmh+0x30);//
               hundredputchar(wmm+0x30);//tenputchar
               (wml+0x30);//
               oneputchar('.');
               putchar(temp/1000+0x30);
               putchar((temp%1000)/100+0x30);
               putchar((temp%100)/10+0x30);
               putchar(temp%10+0x30);
    
               putchar(0x0d);  //Enter

delay_nms(10000);   
    }
}