Fragen zu deinem Sketch

[Gisbert1]

Hallo Jürgen,

ich habe diesen Sketch für meine Zwecke benutzt. Du benutzt sowohl in Zeile 255 OneWire ds(DALLAS_SENSOR_PIN); als auch in Zeile 269 OneWire dallas(DALLAS_SENSOR_PIN); Ich vermute, dass letzteres überflüssig ist. Kannst du dazu etwas sagen?

Ich nehme an, dass dieser Code zwingend notwendig ist. Ist das richtig, und warum?

float ReadSingleOneWireSensor(OneWire ds)
{
  //--- 18B20 stuff
  byte i;
  byte type_s;
  byte data[12];
  byte addr[8];
  float celsius = 12.3;

  if (!ds.search(addr))
  {
    ds.reset_search();
    delay(250);
    return celsius;
  }

  if (OneWire::crc8(addr, 7) != addr[7])
  {
    return celsius;
  }

  //--- 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:
    // Serial.println("Device is not a DS18x20 family device.");
    return celsius;
  }

  ds.reset();
  ds.select(addr);
  ds.write(0x44,1 );  //--- start conversion, use alternatively ds.write(0x44,1) with parasite power on at the end

  delay(1000);        //--- maybe 750ms is enough, maybe not
                      //--- we might do a ds.depower() here, but the reset will take care of it.

  ds.reset();         //--- DS18B20 responds with presence pulse
                      //--- match ROM 0x55, sensor sends ROM-code command ommitted here.
  ds.select(addr);
  ds.write(0xBE);     //--- read scratchpad
  for (i = 0; i < 9; i++)
  {
    //--- we need 9 bytes, 9th byte is CRC, first 8 are data
    data[i] = ds.read();
  }

  //--- 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
    // default is 12 bit resolution, 750 ms conversion time
    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
  };

  celsius = (float)raw / 16.0;    //fahrenheit = celsius * 1.8 + 32.0;

  //---- Check if any reads failed and exit early (to try again).  
  if (isnan(celsius))
  {
    //--- signalize error condition 
    celsius = -99.9;
  };
  return celsius;
}

Viele Grüße Gisbert

[juergs]

_OneWire ds(DALLAS_SENSORPIN); seems to be a relict of previous tests and could be removed from the source. If not referenced by any instantiation object, might be removed by the optimization of the Arduino C++ compiler. So it might cause no harm to code space, eventually needs some additional heap memory.

Code zwingend notwendig ist. Ist das richtig, und warum? I used by: //--- [2] read Dallas-Sensor float theta = ReadSingleOneWireSensor(dallas);

The dallas instance could be changed to ds. But both objects are pointer to the same piece of code. Unless there is no code space problem on the ATtiny, it is harmless but indeed redundant. The sketch worked for me in this configuration, so i didn't notice my fault and moved on to the next project.

Thank you for testing and using this code and sorry for that "inconvenience".

Jürgen