ds18b20.c

DS18B温度测量源代码测量范围 在 １２５到零下２５度

#include <msp430x13x.h>
//#define DELTA 256                       // target DCO = DELTA*(4096) = 1048576 
#define DELTA 244                      // target DCO = DELTA*(4096) = 1048576

unsigned char err_flag=0;
//unsigned char result=0;
//unsigned char result1=0;
unsigned int result=0;
unsigned int result1=0;

void Set_DCO (void);
void delay(unsigned int dd);
void delay1(unsigned char dd1);
void reset(void);
void write_command(unsigned char command);
//unsigned char read_data(void);
unsigned int read_data(void);


void main(void)
{ 
  WDTCTL = WDTPW + WDTHOLD;             // Stop WDT
  Set_DCO();                            // Set DCO
  /*P1DIR |= 0x01;                        // Set P1.0 to output direction

  for (;;)                              
  {
    P1OUT ^= 0x01;                      // Toggle P1.0 using exclusive-OR
    delay(250000);
  }*/
  
  P1OUT |= BIT4;
  P1DIR |= BIT4;
  while(1)
  {
    reset();
    write_command(0xcc);
    write_command(0x44);
    delay1(6);
    reset();
    write_command(0xcc);
    write_command(0xBE);
    result = read_data();
    reset();
    write_command(0xcc);
    write_command(0xBE);
    result1 = read_data();
    _NOP();
    result = 0;
  }
}

void reset(void)
{
  P1OUT &= ~BIT4;
  delay(150);
  P1DIR &= ~BIT4;
//************************
  /*delay(3);
  delay(15);
  if(P1IN&BIT4)
  {err_flag = 1;}
  else err_flag =0;*/
//*****************************
  
  delay(9);
  if(P1IN&BIT4)
  {err_flag = 1;}
  else err_flag =0;    
  delay(125);
  P1OUT |= BIT4;
  P1DIR |= BIT4;
}

void write_command(unsigned char command)
{
  unsigned char i;
  for(i=0;i<8;i++)
  {
   P1OUT &= ~BIT4;
   if(command&0x01)
   {
    //delay(2);
    _NOP();
    _NOP();
    _NOP();
    _NOP();
    //P1OUT |= BIT4;
    P1DIR &= ~BIT4;
   }
   command=command>>1;
   //delay(15);
   delay(20);
   //P1OUT |= BIT4;
   P1DIR &= ~BIT4;
   delay(3);
   P1OUT |= BIT4;
   P1DIR |= BIT4;
  } 
}

//unsigned char read_data(void)
unsigned int read_data(void)
{
  
  //unsigned char data=0,i;
  unsigned int data=0,i;
  //data = 0;
  for(i=0;i<8;i++)
  //for(i=0;i<16;i++)
  {
    P1OUT &= ~BIT4;
    _NOP();
    _NOP();
    _NOP();
    P1DIR &= ~BIT4;
    _NOP();
    if(P1IN&BIT4)
    //{data |= 0x80;}
    {data |= 0x0001;}
    data = data<<1;
    delay(23);
    P1OUT |= BIT4;
    P1DIR |= BIT4;
  }
  return data;
}

void delay(unsigned int dd)
{
  unsigned int i;
  for(i=0;i<dd;i++);
}

void delay1(unsigned char dd1)
{
  unsigned char i;
  for(i=0;i<dd1;i++)
  {
    delay(50000);
  }
}
//------------------------------------------------------------------------------ 
void Set_DCO (void)                     // Set DCO to selected frequency
//------------------------------------------------------------------------------ 
{
//#define DELTA 900                       // target DCO = DELTA*(4096) = 3686400
//#define DELTA 256                       // target DCO = DELTA*(4096) = 1048576  
//#define DELTA 64                        // target DCO = DELTA*(4096) = 262144
  unsigned int Compare, Oldcapture = 0;

  BCSCTL1 |= DIVA_3;                    // ACLK= LFXT1CLK/8
  CCTL2 = CM_1 + CCIS_1 + CAP;          // CAP, ACLK
  TACTL = TASSEL_2 + MC_2 + TACLR;      // SMCLK, cont-mode, clear

  while (1)
  {
    while (!(CCIFG & CCTL2));           // Wait until capture occured
    CCTL2 &= ~CCIFG;                    // Capture occured, clear flag
    Compare = CCR2;                     // Get current captured SMCLK 
    Compare = Compare - Oldcapture;     // SMCLK difference
    Oldcapture = CCR2;                  // Save current captured SMCLK

    if (DELTA == Compare) break;        // If equal, leave "while(1)"
    else if (DELTA < Compare)           // DCO is too fast, slow it down
    {
      DCOCTL--;
      if (DCOCTL == 0xFF) BCSCTL1--;    // Did DCO role under?, Sel lower RSEL
    }
    else
    {                      
      DCOCTL++;
      if (DCOCTL == 0x00) BCSCTL1++;    // Did DCO role over? Sel higher RSEL
    }
  }  
  CCTL2 = 0;                            // Stop CCR2
  TACTL = 0;                            // Stop Timer_A
  BCSCTL1 &= ~DIVA_3;
}