Arduino example: Multiple DS18B20 in a task.

[Cellie]

Simple example for Arduino IDE to poll multiple DS18B20 sensors in a separate task.

Code available on https://github.com/CelliesProjects/esp3 ... 18B20-task
EDIT: Fixed off-by-one error.

Code: Select all

/*************************************************************************************************
 * 
 *     Read multiple DS18B20 Dallas sensors in a task.
 *     
 *     For ESP32 by CelliesProjects 2017.
 *     
 *     Code adapted from https://www.pjrc.com/teensy/td_libs_OneWire.html
 * 
 ************************************************************************************************/
//#define SHOW_DALLAS_ERROR        // uncomment to show Dallas ( CRC ) errors on Serial.
#define ONEWIRE_PIN           5    // OneWire Dallas sensors are connected to this pin
#define MAX_NUMBER_OF_SENSORS 3    // maximum number of Dallas sensors

#include "OneWire.h"               //https://github.com/CelliesProjects/OneWire

OneWire  ds( ONEWIRE_PIN );        // (a 4.7K pull-up resistor is necessary)

struct sensorStruct
{
  byte addr[8];
  float temp;
  String name;
} sensor[MAX_NUMBER_OF_SENSORS];

byte numberOfFoundSensors;

void setup()
{
  
  Serial.begin( 115200 );
  Serial.println( "\n\nMultiple DS18B20 sensors as task ESP32 example." );

  numberOfFoundSensors = searchDallasSensors();

  if ( numberOfFoundSensors )
  {
    xTaskCreatePinnedToCore(
      tempTask,                       /* Function to implement the task */
      "tempTask ",                    /* Name of the task */
      4000,                           /* Stack size in words */
      NULL,                           /* Task input parameter */
      5,                              /* Priority of the task */
      NULL,                           /* Task handle. */
      1);                             /* Core where the task should run */
  }
}


void loop()
{
  if ( numberOfFoundSensors )
  {
    Serial.println( String( millis() / 1000.0 ) + " sec" );
    for ( byte thisSensor = 0; thisSensor < numberOfFoundSensors; thisSensor++ )
    {
      Serial.println( sensor[thisSensor].name + ": " + String( sensor[thisSensor].temp / 16.0 ) + "°C" );
    }
  }
  else
  {
    Serial.println( "No Dallas sensors found." );
  }
  vTaskDelay( 500 / portTICK_PERIOD_MS );
}

static void tempTask( void * pvParameters )
{
  while (1)
  {
    for ( byte thisSensor = 0; thisSensor < numberOfFoundSensors; thisSensor++)
    {
      ds.reset();
      ds.select( sensor[thisSensor].addr );
      ds.write( 0x44, 0);        // start conversion, with parasite power off at the end
    }

    vTaskDelay( 750 / portTICK_PERIOD_MS); //wait for conversion ready

    for ( byte thisSensor = 0; thisSensor < numberOfFoundSensors; thisSensor++)
    {
      byte data[12];
      ds.reset();
      ds.select( sensor[thisSensor].addr );
      ds.write( 0xBE );         // Read Scratchpad

      //Serial.print( "Sensor " );Serial.print( thisSensor ); Serial.print("  Data = ");
      //Serial.println( present, HEX );
      //Serial.print(" ");
      for ( byte i = 0; i < 9; i++)
      { // we need 9 bytes
        data[i] = ds.read(  );
        //Serial.print(data[i], HEX);
        //Serial.print(" ");
      }
      //Serial.println();

      byte type_s;
      // the first ROM byte indicates which chip
      switch ( sensor[thisSensor].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:
#ifdef SHOW_DALLAS_ERROR
          Serial.println("Device is not a DS18x20 family device.");
#endif
          return;
      }

      int16_t raw;
      if ( OneWire::crc8(data, 8) != data[8])
      {
#ifdef SHOW_DALLAS_ERROR
        // CRC of temperature reading indicates an error, so we print a error message and discard this reading
        Serial.print( millis() / 1000.0 ); Serial.print( " - CRC error from device " ); Serial.println( thisSensor );
#endif
      }
      else
      {
        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
        }
        sensor[thisSensor].temp = raw;
      }
    }
  }
}

byte searchDallasSensors()
{
  Serial.println("Searching Dallas temperature sensors...");
  byte counter = 0;
  byte currentAddr[8];
  while ( ds.search( currentAddr ) && counter < MAX_NUMBER_OF_SENSORS )
  {
    //counter++;
    Serial.write( "Sensor "); Serial.print( counter ); Serial.print( ":" );
    for ( byte i = 0; i < 8; i++) {
      //Serial.write(' ');
      //Serial.print( currentAddr[i], HEX );
      sensor[counter].addr[i] = currentAddr[i];
      sensor[counter].name = "Sensor" + String( counter );
    }
    counter++;
  }
  Serial.print( counter ); Serial.println( " sensors found." );
  return counter;
}