Petras Saduikis / Mbed 2 deprecated OneWireCRC

Now supports DS18B20 and DS18S20 Maxim/Dallas one-wire thermometer devices. Also supports DS18S20 in 9, 10, 11, and 12 bit resolution modes. 'Use Address' mode now checks if the correct device type is present, and informs the user which device to use. Correct temperature conversion times now used in non-parasitic mode. The device should be placed at least 6 inches (15 cm) from the mbed board in order to accurately read ambient temperature.

Dependencies:   mbed

DS18S20.cpp

Committer:
snatch59
Date:
2010-01-03
Revision:
0:01a6a40578c9

File content as of revision 0:01a6a40578c9:

/*
* DS18S20. Maxim DS18S20 One-Wire Thermometer. 
* Uses the OneWireCRC library.
*
* Copyright (C) <2010> Petras Saduikis <petras@petras.co.uk>
*
* This file is part of OneWireThermometer.
*
* OneWireThermometer is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* 
* OneWireThermometer is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with OneWireThermometer.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "DS18S20.h"
#include "DebugTrace.h"

DebugTrace pc_ds18S20(ON, TO_SERIAL);

DS18S20::DS18S20(bool crcOn, bool useAddr, bool parasitic, PinName pin) : 
    OneWireThermometer(crcOn, useAddr, parasitic, pin, DS18S20_ID)
{
}

float DS18S20::calculateTemperature(BYTE* data)
{    
    // DS18S20 basic resolution is always 9 bits, which can be enhanced as follows
    bool signBit = false;
    if (data[TEMPERATURE_MSB] & 0x80) signBit = true;
        
    int read_temp = (data[TEMPERATURE_MSB] << 8) + data[TEMPERATURE_LSB];
    if (signBit)
    {
        read_temp = (read_temp ^ 0xFFFF) + 1;    // two's complement
        read_temp *= -1;
    }
                 
    float readTemp = (float)read_temp/2 ;            // divide by 2
    pc_ds18S20.traceOut("TEMP_READ: %f \r\n", readTemp);     // 9 bit resolution value
               
    // convert to real temperature
    float tempCount = float(data[COUNT_PER_DEG_BYTE] - data[COUNT_REMAIN_BYTE])/(float)data[COUNT_PER_DEG_BYTE];        
    float realTemp = (readTemp - 0.25) + tempCount;        
    pc_ds18S20.traceOut("Temperature: %f \r\n", realTemp);   // enhanced resolution value
    
    return realTemp;
}