Kai Riedel / DS18B20

Library for Programmable Resolution 1-Wire Digital ThermometerDS18B20

Dependents:   DS18B20_HGC

DS18S20.cpp@0:21c0c97a5d7c, 2011-02-03 (annotated)

Committer:
kriedel
Date:
Thu Feb 03 12:10:20 2011 +0000
Revision:
0:21c0c97a5d7c

        

        
Who changed what in which revision?

        

            
                
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/*





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* DS18S20. Maxim DS18S20 One-Wire Thermometer. 





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* Uses the OneWireCRC library.





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*





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* Copyright (C) <2010> Petras Saduikis <petras@petras.co.uk>





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*





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* This file is part of OneWireThermometer.





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*





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* OneWireThermometer is free software: you can redistribute it and/or modify





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* it under the terms of the GNU General Public License as published by





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* the Free Software Foundation, either version 3 of the License, or





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* (at your option) any later version.





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* 





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* OneWireThermometer is distributed in the hope that it will be useful,





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* but WITHOUT ANY WARRANTY; without even the implied warranty of





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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the





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* GNU General Public License for more details.





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*





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* You should have received a copy of the GNU General Public License





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* along with OneWireThermometer.  If not, see <http://www.gnu.org/licenses/>.





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*/





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#include "DS18S20.h"





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#include "DebugTrace.h"





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DebugTrace pc_ds18S20(ON, TO_SERIAL);





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DS18S20::DS18S20(bool crcOn, bool useAddr, bool parasitic, PinName pin) : 





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    OneWireThermometer(crcOn, useAddr, parasitic, pin, DS18S20_ID)





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{





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}





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float DS18S20::calculateTemperature(BYTE* data)





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{    





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    // DS18S20 basic resolution is always 9 bits, which can be enhanced as follows





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    bool signBit = false;





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    if (data[TEMPERATURE_MSB] & 0x80) signBit = true;





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    int read_temp = (data[TEMPERATURE_MSB] << 8) + data[TEMPERATURE_LSB];





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    if (signBit)





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    {





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        read_temp = (read_temp ^ 0xFFFF) + 1;    // two's complement





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        read_temp *= -1;





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    }





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    float readTemp = (float)read_temp/2 ;            // divide by 2





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    pc_ds18S20.traceOut("TEMP_READ: %f \r\n", readTemp);     // 9 bit resolution value





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    // convert to real temperature





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    float tempCount = float(data[COUNT_PER_DEG_BYTE] - data[COUNT_REMAIN_BYTE])/(float)data[COUNT_PER_DEG_BYTE];        





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    float realTemp = (readTemp - 0.25) + tempCount;        





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    pc_ds18S20.traceOut("Temperature: %f \r\n", realTemp);   // enhanced resolution value





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    return realTemp;





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}