Felícito Manzano
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OneWireCRC
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DS18S20.cpp
00001 /* 00002 * DS18S20. Maxim DS18S20 One-Wire Thermometer. 00003 * Uses the OneWireCRC library. 00004 * 00005 * Copyright (C) <2010> Petras Saduikis <petras@petras.co.uk> 00006 * 00007 * This file is part of OneWireThermometer. 00008 * 00009 * OneWireThermometer is free software: you can redistribute it and/or modify 00010 * it under the terms of the GNU General Public License as published by 00011 * the Free Software Foundation, either version 3 of the License, or 00012 * (at your option) any later version. 00013 * 00014 * OneWireThermometer is distributed in the hope that it will be useful, 00015 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00016 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00017 * GNU General Public License for more details. 00018 * 00019 * You should have received a copy of the GNU General Public License 00020 * along with OneWireThermometer. If not, see <http://www.gnu.org/licenses/>. 00021 */ 00022 00023 #include "DS18S20.h" 00024 #include "DebugTrace.h" 00025 00026 DebugTrace pc_ds18S20(ON, TO_SERIAL); 00027 00028 DS18S20::DS18S20(bool crcOn, bool useAddr, bool parasitic, PinName pin) : 00029 OneWireThermometer(crcOn, useAddr, parasitic, pin, DS18S20_ID) 00030 { 00031 } 00032 00033 float DS18S20::calculateTemperature(BYTE* data) 00034 { 00035 // DS18S20 basic resolution is always 9 bits, which can be enhanced as follows 00036 bool signBit = false; 00037 if (data[TEMPERATURE_MSB] & 0x80) signBit = true; 00038 00039 int read_temp = (data[TEMPERATURE_MSB] << 8) + data[TEMPERATURE_LSB]; 00040 if (signBit) 00041 { 00042 read_temp = (read_temp ^ 0xFFFF) + 1; // two's complement 00043 read_temp *= -1; 00044 } 00045 00046 float readTemp = (float)read_temp/2 ; // divide by 2 00047 pc_ds18S20.traceOut("TEMP_READ: %f \r\n", readTemp); // 9 bit resolution value 00048 00049 // convert to real temperature 00050 float tempCount = float(data[COUNT_PER_DEG_BYTE] - data[COUNT_REMAIN_BYTE])/(float)data[COUNT_PER_DEG_BYTE]; 00051 float realTemp = (readTemp - 0.25) + tempCount; 00052 pc_ds18S20.traceOut("Temperature: %f \r\n", realTemp); // enhanced resolution value 00053 00054 return realTemp; 00055 }
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