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/*
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* DS18B20. Maxim DS18B20 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 "DS18B20.h"
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#include "DebugTrace.h"
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DebugTrace pc_ds18B20(ON, TO_SERIAL);
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DS18B20::DS18B20(bool crcOn, bool useAddr, bool parasitic, PinName pin) :
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OneWireThermometer(crcOn, useAddr, parasitic, pin, DS18B20_ID)
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{
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}
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void DS18B20::setResolution(eResolution resln)
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{
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// as the write to the configuration register involves a write to the
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// high and low alarm bytes, need to read these registers first
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// and copy them back on the write
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BYTE read_data[THERMOM_SCRATCHPAD_SIZE];
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BYTE write_data[ALARM_CONFIG_SIZE];
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if (readAndValidateData(read_data))
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{
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// copy alarm and config data to write data
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for (int k = 2; k < 5; k++)
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{
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write_data[k - 2] = read_data[k];
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}
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int config = write_data[2];
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config &= 0x9F;
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config ^= (resln << 5);
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write_data[2] = config;
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resetAndAddress();
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oneWire.writeByte(WRITESCRATCH);
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for (int k = 0; k < 3; k++)
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{
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oneWire.writeByte(write_data[k]);
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}
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// remember it so we can use the correct delay in reading the temperature
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// for parasitic power
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resolution = resln;
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}
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}
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float DS18B20::calculateTemperature(BYTE* data)
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{
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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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int resolution = (data[CONFIG_REG_BYTE] & 0x60) >> 5; // mask off bits 6,5 and move to 1,0
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switch (resolution)
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{
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case nineBit: // 0.5 deg C increments
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read_temp &= 0xFFF8; // bits 2,1,0 are undefined
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pc_ds18B20.traceOut("9 bit resolution ...\r\n");
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break;
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case tenBit: // 0.25 deg C increments
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read_temp &= 0xFFFC; // bits 1,0 are undefined
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pc_ds18B20.traceOut("10 bit resolution ...\r\n");
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break;
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case elevenBit: // 0.125 deg C increments
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read_temp &= 0xFFFE; // bit 0 is undefined
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pc_ds18B20.traceOut("11 bit resolution ...\r\n");
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break;
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case twelveBit: // 0.0625 deg C increments
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pc_ds18B20.traceOut("12 bit resolution ...\r\n");
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break;
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}
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float realTemp = (float)read_temp/16 ;
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pc_ds18B20.traceOut("TEMP_READ/REAL TEMP: %f \r\n", realTemp);
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return realTemp;
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} |
gavin beardall