TemperatureReaderOneWire.cpp

#include "TemperatureReaderOneWire.h"

int read_temperature(float& temperature, OneWire& ds) {
  char cel[8];
  byte i;
  byte present = 0;
  byte type_s;
  byte data[12];
  byte addr[8];
  float celsius;
 
  if ( !ds.search(addr)) {
    ds.reset_search();
    delay(5000);
    ds.reset();
    ds.skip();
    ds.write(0x44);
    delay(1000);
    return -1;
  }
 
//  Serial.print("ROM =");
//  for( i = 0; i < 8; i++) {
//    Serial.write(' ');
//    Serial.print(addr[i], HEX);
//  }
 
  if (OneWire::crc8(addr, 7) != addr[7]) {
      return -2;
  }

  // the first ROM byte indicates which chip
  switch (addr[0]) {
    case 0x10:
      //Serial.println("  Chip = DS18S20");  // or old DS1820
      type_s = 1;
      break;
    case 0x28:
      //Serial.println("  Chip = DS18B20");
      type_s = 0;
      break;
    case 0x22:
      //Serial.println("  Chip = DS1822");
      type_s = 0;
      break;
    default:
      return -3;
  }
 
         // start conversion, with parasite power on at the end
 
 
  present = ds.reset();
  ds.select(addr);    
  ds.write(0xBE);         // Read Scratchpad
 
//  Serial.print("  Data = ");
//  Serial.print(present, HEX);
//  Serial.print(" ");
  for ( i = 0; i < 9; i++) {           // we need 9 bytes
    data[i] = ds.read();
//    Serial.print(data[i], HEX);
//    Serial.print(" ");
  }
//  Serial.print(" CRC=");
//  Serial.print(OneWire::crc8(data, 8), HEX);
//  Serial.println();
 
  // Convert the data to actual temperature
  // because the result is a 16 bit signed integer, it should
  // be stored to an "int16_t" type, which is always 16 bits
  // even when compiled on a 32 bit processor.
  int16_t raw = (data[1] << 8) | data[0];
  if (type_s) {
    raw = raw << 3; // 9 bit resolution default
    if (data[7] == 0x10) {
      // "count remain" gives full 12 bit resolution
      raw = (raw & 0xFFF0) + 12 - data[6];
    }
  } else {
    byte cfg = (data[4] & 0x60);
    // at lower res, the low bits are undefined, so let's zero them
    if (cfg == 0x00) raw = raw & ~7;  // 9 bit resolution, 93.75 ms
    else if (cfg == 0x20) raw = raw & ~3; // 10 bit res, 187.5 ms
    else if (cfg == 0x40) raw = raw & ~1; // 11 bit res, 375 ms
    //// default is 12 bit resolution, 750 ms conversion time
  }
  celsius = (float)raw / 16.0;
  temperature = celsius;
  //sprintf(cel,"%f",celsius);
  //fahrenheit = celsius * 1.8 + 32.0;
  //Serial.print("  Temperature = ");
  //Serial.print(celsius);
  //Serial.print(" Celsius, ");
  //Serial.print(fahrenheit);
  //Serial.println(" Fahrenheit");
 
  return 0;
}