Tony Mudd / Mbed 2 deprecated MultipleDS18B20

Program to read the temperature from multiple DS18B20 sensors on the same pin. The original library/code came from Petras Saduikis (see http://mbed.org/users/snatch59/programs/OneWireCRC/gpdz56), but I've modified it to remember the address of multiple sensors all connected to the same data pin. My sample program displays the temperature of each device in turn. If you want to see more of what's going on behind the scenes turn on the debug by setting DebugTrace pc(OFF, TO_SERIAL); to ON (instead of OFF) in the couple of places it's used - it will log the device addresses as they are found etc. The addresses are set in the devices at the factory - I don't think they can be changed, the search always seems to find them in the same order, but this won't be anything to do with the way you've plugged them in. I've had a play with up to 7 sensors (the code has a limit of 10 hardwired in it, but this would be easy to change)

Dependencies:   mbed

DS18B20.cpp

Committer:
tonymudd
Date:
2011-07-17
Revision:
0:fb8b6da96a8b

File content as of revision 0:fb8b6da96a8b:

/*
* DS18B20. Maxim DS18B20 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 "DS18B20.h"
#include "DebugTrace.h"

DebugTrace pc_ds18B20(OFF, TO_SERIAL);

DS18B20::DS18B20( PinName pin) : 
    OneWireThermometer(pin, DS18B20_ID)
{
}

void DS18B20::setResolution(eResolution resln)
{
    // as the write to the configuration register involves a write to the
    // high and low alarm bytes, need to read these registers first
    // and copy them back on the write
    
    BYTE read_data[THERMOM_SCRATCHPAD_SIZE];
    BYTE write_data[ALARM_CONFIG_SIZE];
    
    if (readAndValidateData(read_data))
    {
        // copy alarm and config data to write data
        for (int k = 2; k < 5; k++)
        {
            write_data[k - 2] = read_data[k];
        }
        int config = write_data[2];
        config &= 0x9F;
        config ^= (resln << 5);
        write_data[2] = config;
        
        resetAndAddress();
        oneWire.writeByte(WRITESCRATCH);
        for (int k = 0; k < 3; k++)
        {
            oneWire.writeByte(write_data[k]);
        }
        
        // remember it so we can use the correct delay in reading the temperature
        // for parasitic power
        resolution = resln; 
    }
}

float DS18B20::calculateTemperature(BYTE* data)
{
    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;
    }
    
    int resolution = (data[CONFIG_REG_BYTE] & 0x60) >> 5; // mask off bits 6,5 and move to 1,0
    switch (resolution)
    {
        case nineBit:    // 0.5 deg C increments
            read_temp &= 0xFFF8;                // bits 2,1,0 are undefined
            //pc_ds18B20.traceOut("9 bit resolution ...\r\n");
            break;
        case tenBit:     // 0.25 deg C increments
            read_temp &= 0xFFFC;                // bits 1,0 are undefined
            //pc_ds18B20.traceOut("10 bit resolution ...\r\n");
            break;
        case elevenBit:  // 0.125 deg C increments
            read_temp &= 0xFFFE;                // bit 0 is undefined
            //pc_ds18B20.traceOut("11 bit resolution ...\r\n");
            break;
        case twelveBit:  // 0.0625 deg C increments
            //pc_ds18B20.traceOut("12 bit resolution ...\r\n");
            break;
    }
    float realTemp = (float)read_temp/16 ;
                 
    pc_ds18B20.traceOut("TEMP_READ/REAL TEMP: %f \r\n", realTemp); 
               
    return realTemp;
}