jack zen / DS18S20

DS18B20

Dependents:   DS1820_HelloWorld

DS18S20.cpp@0:d7eea3b21e1d, 2017-09-06 (annotated)

Committer:
jack__zen
Date:
Wed Sep 06 05:35:00 2017 +0000
Revision:
0:d7eea3b21e1d
ds18s20

Who changed what in which revision?

UserRevisionLine numberNew contents of line
jack__zen 0:d7eea3b21e1d 1 /*
jack__zen 0:d7eea3b21e1d 2 * DS18S20. Maxim DS18S20 One-Wire Thermometer.
jack__zen 0:d7eea3b21e1d 3 * Uses the OneWireCRC library.
jack__zen 0:d7eea3b21e1d 4 *
jack__zen 0:d7eea3b21e1d 5 * Copyright (C) <2010> Petras Saduikis <petras@petras.co.uk>
jack__zen 0:d7eea3b21e1d 6 *
jack__zen 0:d7eea3b21e1d 7 * This file is part of OneWireThermometer.
jack__zen 0:d7eea3b21e1d 8 *
jack__zen 0:d7eea3b21e1d 9 * OneWireThermometer is free software: you can redistribute it and/or modify
jack__zen 0:d7eea3b21e1d 10 * it under the terms of the GNU General Public License as published by
jack__zen 0:d7eea3b21e1d 11 * the Free Software Foundation, either version 3 of the License, or
jack__zen 0:d7eea3b21e1d 12 * (at your option) any later version.
jack__zen 0:d7eea3b21e1d 13 *
jack__zen 0:d7eea3b21e1d 14 * OneWireThermometer is distributed in the hope that it will be useful,
jack__zen 0:d7eea3b21e1d 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
jack__zen 0:d7eea3b21e1d 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
jack__zen 0:d7eea3b21e1d 17 * GNU General Public License for more details.
jack__zen 0:d7eea3b21e1d 18 *
jack__zen 0:d7eea3b21e1d 19 * You should have received a copy of the GNU General Public License
jack__zen 0:d7eea3b21e1d 20 * along with OneWireThermometer. If not, see <http://www.gnu.org/licenses/>.
jack__zen 0:d7eea3b21e1d 21 */
jack__zen 0:d7eea3b21e1d 22
jack__zen 0:d7eea3b21e1d 23 #include "DS18S20.h"
jack__zen 0:d7eea3b21e1d 24 #include "DebugTrace.h"
jack__zen 0:d7eea3b21e1d 25
jack__zen 0:d7eea3b21e1d 26 DebugTrace pc_ds18S20(ON, TO_SERIAL);
jack__zen 0:d7eea3b21e1d 27
jack__zen 0:d7eea3b21e1d 28 DS18S20::DS18S20(bool crcOn, bool useAddr, bool parasitic, PinName pin) :
jack__zen 0:d7eea3b21e1d 29 OneWireThermometer(crcOn, useAddr, parasitic, pin, DS18S20_ID)
jack__zen 0:d7eea3b21e1d 30 {
jack__zen 0:d7eea3b21e1d 31 }
jack__zen 0:d7eea3b21e1d 32
jack__zen 0:d7eea3b21e1d 33 float DS18S20::calculateTemperature(BYTE* data)
jack__zen 0:d7eea3b21e1d 34 {
jack__zen 0:d7eea3b21e1d 35 // DS18S20 basic resolution is always 9 bits, which can be enhanced as follows
jack__zen 0:d7eea3b21e1d 36 bool signBit = false;
jack__zen 0:d7eea3b21e1d 37 if (data[TEMPERATURE_MSB] & 0x80) signBit = true;
jack__zen 0:d7eea3b21e1d 38
jack__zen 0:d7eea3b21e1d 39 int read_temp = (data[TEMPERATURE_MSB] << 8) + data[TEMPERATURE_LSB];
jack__zen 0:d7eea3b21e1d 40 if (signBit)
jack__zen 0:d7eea3b21e1d 41 {
jack__zen 0:d7eea3b21e1d 42 read_temp = (read_temp ^ 0xFFFF) + 1; // two's complement
jack__zen 0:d7eea3b21e1d 43 read_temp *= -1;
jack__zen 0:d7eea3b21e1d 44 }
jack__zen 0:d7eea3b21e1d 45
jack__zen 0:d7eea3b21e1d 46 float readTemp = (float)read_temp/2 ; // divide by 2
jack__zen 0:d7eea3b21e1d 47 pc_ds18S20.traceOut("TEMP_READ: %f \r\n", readTemp); // 9 bit resolution value
jack__zen 0:d7eea3b21e1d 48
jack__zen 0:d7eea3b21e1d 49 // convert to real temperature
jack__zen 0:d7eea3b21e1d 50 float tempCount = float(data[COUNT_PER_DEG_BYTE] - data[COUNT_REMAIN_BYTE])/(float)data[COUNT_PER_DEG_BYTE];
jack__zen 0:d7eea3b21e1d 51 float realTemp = (readTemp - 0.25) + tempCount;
jack__zen 0:d7eea3b21e1d 52 pc_ds18S20.traceOut("Temperature: %f \r\n", realTemp); // enhanced resolution value
jack__zen 0:d7eea3b21e1d 53
jack__zen 0:d7eea3b21e1d 54 return realTemp;
jack__zen 0:d7eea3b21e1d 55 }