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.
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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