PIC: DS18S20 e DS18B20

Neste post mostrarei como utilizar o sensor de temperatura DS18B20 e DS18S20 com o PIC. Este sensor utiliza o protocolo One-Wire, e requer apenas um fio de comunicação.

Mostrarei o jeito mais simples de realizar a leitura do sensor. Criei uma função que faz a leitura e salva em uma string prontinha pra ser escrita num display de LCD.

BIBLIOTECA

#include <built_in.h>

#define RES9 3
#define RES10 2
#define RES11 1
#define RES12 0

static char resolution = 0;

void DS18B20_getTemp( char *DS18x20_PORT, char DS18x20_PIN, char *outTemp )
{
unsigned temp, Temp_f;
char i;

 Ow_Reset( DS18x20_PORT, DS18x20_PIN );
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0xCC );  //Skip ROM
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0x44 );  //Inicia a conversao
    
 //Espera o tempo da conversao
 for(i = 0; i < (1 << (3 - resolution)); i++)
    Delay_ms( 95 );
    
 Ow_Reset( DS18x20_PORT, DS18x20_PIN );
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0xCC );  //Skip ROM
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0xBE );  //Inicia a leitura
    
 Lo(temp) =  Ow_Read( DS18x20_PORT, DS18x20_PIN );
 Hi(temp) =  Ow_Read( DS18x20_PORT, DS18x20_PIN );
    
 outTemp[0] = 32;
 outTemp[4] = '.';

 if(Hi(temp).B7)
 {
     temp = ~temp + 1;
     outTemp[0] = '-';
 }
        
 temp <<= 4;
 Lo(temp) >>= ( 4 + resolution );
 Temp_f = Lo(temp) * 625;

 outTemp[1] = Hi(temp) / 100 + '0';
 outTemp[2] = (Hi(temp) / 10) % 10 + '0';
 outTemp[3] = Hi(temp) % 10 + '0';
 outTemp[5] = Temp_f / 1000 + '0';
 outTemp[6] = (Temp_f / 100) % 10 + '0';
 outTemp[7] = (Temp_f / 10) % 10 + '0';
 outTemp[8] = (Temp_f % 10) + '0';
 outTemp[9] = 223; //simbolo de graus 
 outTemp[10] = 'C';
 outTemp[11] = 0;
}

void DS18S20_getTemp( char *DS18x20_PORT, char DS18x20_PIN, char *outTemp )
{
unsigned temp;
 Ow_Reset( DS18x20_PORT, DS18x20_PIN );
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0xCC );  //Skip ROM
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0x44 );  //Inicia a conversao
    
 //Espera o tempo da conversao
 Delay_ms( 750 );
    
 Ow_Reset( DS18x20_PORT, DS18x20_PIN );
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0xCC );  //Skip ROM
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0xBE );  //Inicia a leitura
    
 Lo(temp) =  Ow_Read( DS18x20_PORT, DS18x20_PIN );
 Hi(temp) =  Ow_Read( DS18x20_PORT, DS18x20_PIN );
    
 outTemp[0] = 32;
 outTemp[4] = '.';
 
 if(Hi(temp).B7)
 {
   Lo(temp) = ~Lo(temp);
   outTemp[0] = '-';
 }
        
 outTemp[5] = (Lo(temp).B0 == 1) ? '5' : '0';
 Lo(temp) >>= 1;
 outTemp[1] = Lo(temp) / 100 + '0';
 outTemp[2] = (Lo(temp) / 10) % 10 + '0';
 outTemp[3] = Lo(temp) % 10 + '0';
 outTemp[6] = 223;
 outTemp[7] = 'C';
 outTemp[8] = 0;
}

void DS18B20_Set_Resolution( char *DS18x20_PORT, char DS18x20_PIN, char res )
{
 resolution = res;
 Ow_Reset( DS18x20_PORT, DS18x20_PIN );
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0xCC );  //Skip ROM
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0x4E );  //Write Scratchpad
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0 );  //Th
 Ow_Write( DS18x20_PORT, DS18x20_PIN, 0 );  //Tl
 Ow_Write( DS18x20_PORT, DS18x20_PIN, (0x1F | (res << 5)) );  //Config
 Ow_Reset( DS18x20_PORT, DS18x20_PIN );
}

DS18B20_getTemp( char *DS18x20_PORT, char DS18x20_PIN, char *outTemp )
DS18S20_getTemp( char *DS18x20_PORT, char DS18x20_PIN, char *outTemp )

*DS18x20_PORT - Porta onde está conectado o sensor.

DS18x20_PIN - Pino onde está conectado o sensor.

*outTemp - String onde será salvo o valor da temperatura.

DS18B20_Set_Resolution( char *DS18x20_PORT, char DS18x20_PIN, char res )

res - Resolução:

RES9 - 9 Bits de resolução

RES10 - 10 Bits Bits de resolução

RES11 - 11 Bits Bits de resolução

RES12 - 12 Bits Bits de resolução

EXEMPLO:

MikroC PRO PIC

sbit LCD_RS at RB0_bit;
sbit LCD_EN at RB1_bit;
sbit LCD_D4 at RB2_bit;
sbit LCD_D5 at RB3_bit;
sbit LCD_D6 at RB4_bit;
sbit LCD_D7 at RB5_bit;

sbit LCD_RS_Direction at TRISB0_bit;
sbit LCD_EN_Direction at TRISB1_bit;
sbit LCD_D4_Direction at TRISB2_bit;
sbit LCD_D5_Direction at TRISB3_bit;
sbit LCD_D6_Direction at TRISB4_bit;
sbit LCD_D7_Direction at TRISB5_bit;

//COPIE E COLE O CÓDIGO ACIMA AQUI!!!

char Temperatura[12];

void main()
{
   CMCON = 0x07;
   Lcd_Init();
   Lcd_Cmd( _LCD_CURSOR_OFF );
   
   while(1)
   {
      //Faz a leitura do sensor DS18B20 conectado no pino RA0
      Ds18B20_getTemp( &PORTA, 0, Temperatura );
      
      Lcd_Out( 1, 1, Temperatura );
      
      //Faz a leitura do sensor DS18S20 conectado no pino RA1
      Ds18S20_getTemp( &PORTA, 1, Temperatura );
      
      Lcd_Out( 2, 1, Temperatura );
   }
}