Dependencies:   mbed

Committer:
gbeardall
Date:
Mon Oct 17 10:42:00 2011 +0000
Revision:
0:2f78e3dca55d

        

Who changed what in which revision?

UserRevisionLine numberNew contents of line
gbeardall 0:2f78e3dca55d 1 /*
gbeardall 0:2f78e3dca55d 2 * DS18S20. Maxim DS18S20 One-Wire Thermometer.
gbeardall 0:2f78e3dca55d 3 * Uses the OneWireCRC library.
gbeardall 0:2f78e3dca55d 4 *
gbeardall 0:2f78e3dca55d 5 * Copyright (C) <2010> Petras Saduikis <petras@petras.co.uk>
gbeardall 0:2f78e3dca55d 6 *
gbeardall 0:2f78e3dca55d 7 * This file is part of OneWireThermometer.
gbeardall 0:2f78e3dca55d 8 *
gbeardall 0:2f78e3dca55d 9 * OneWireThermometer is free software: you can redistribute it and/or modify
gbeardall 0:2f78e3dca55d 10 * it under the terms of the GNU General Public License as published by
gbeardall 0:2f78e3dca55d 11 * the Free Software Foundation, either version 3 of the License, or
gbeardall 0:2f78e3dca55d 12 * (at your option) any later version.
gbeardall 0:2f78e3dca55d 13 *
gbeardall 0:2f78e3dca55d 14 * OneWireThermometer is distributed in the hope that it will be useful,
gbeardall 0:2f78e3dca55d 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
gbeardall 0:2f78e3dca55d 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
gbeardall 0:2f78e3dca55d 17 * GNU General Public License for more details.
gbeardall 0:2f78e3dca55d 18 *
gbeardall 0:2f78e3dca55d 19 * You should have received a copy of the GNU General Public License
gbeardall 0:2f78e3dca55d 20 * along with OneWireThermometer. If not, see <http://www.gnu.org/licenses/>.
gbeardall 0:2f78e3dca55d 21 */
gbeardall 0:2f78e3dca55d 22
gbeardall 0:2f78e3dca55d 23 #include "DS18S20.h"
gbeardall 0:2f78e3dca55d 24 #include "DebugTrace.h"
gbeardall 0:2f78e3dca55d 25
gbeardall 0:2f78e3dca55d 26 DebugTrace pc_ds18S20(ON, TO_SERIAL);
gbeardall 0:2f78e3dca55d 27
gbeardall 0:2f78e3dca55d 28 DS18S20::DS18S20(bool crcOn, bool useAddr, bool parasitic, PinName pin) :
gbeardall 0:2f78e3dca55d 29 OneWireThermometer(crcOn, useAddr, parasitic, pin, DS18S20_ID)
gbeardall 0:2f78e3dca55d 30 {
gbeardall 0:2f78e3dca55d 31 }
gbeardall 0:2f78e3dca55d 32
gbeardall 0:2f78e3dca55d 33 float DS18S20::calculateTemperature(BYTE* data)
gbeardall 0:2f78e3dca55d 34 {
gbeardall 0:2f78e3dca55d 35 // DS18S20 basic resolution is always 9 bits, which can be enhanced as follows
gbeardall 0:2f78e3dca55d 36 bool signBit = false;
gbeardall 0:2f78e3dca55d 37 if (data[TEMPERATURE_MSB] & 0x80) signBit = true;
gbeardall 0:2f78e3dca55d 38
gbeardall 0:2f78e3dca55d 39 int read_temp = (data[TEMPERATURE_MSB] << 8) + data[TEMPERATURE_LSB];
gbeardall 0:2f78e3dca55d 40 if (signBit)
gbeardall 0:2f78e3dca55d 41 {
gbeardall 0:2f78e3dca55d 42 read_temp = (read_temp ^ 0xFFFF) + 1; // two's complement
gbeardall 0:2f78e3dca55d 43 read_temp *= -1;
gbeardall 0:2f78e3dca55d 44 }
gbeardall 0:2f78e3dca55d 45
gbeardall 0:2f78e3dca55d 46 float readTemp = (float)read_temp/2 ; // divide by 2
gbeardall 0:2f78e3dca55d 47 pc_ds18S20.traceOut("TEMP_READ: %f \r\n", readTemp); // 9 bit resolution value
gbeardall 0:2f78e3dca55d 48
gbeardall 0:2f78e3dca55d 49 // convert to real temperature
gbeardall 0:2f78e3dca55d 50 float tempCount = float(data[COUNT_PER_DEG_BYTE] - data[COUNT_REMAIN_BYTE])/(float)data[COUNT_PER_DEG_BYTE];
gbeardall 0:2f78e3dca55d 51 float realTemp = (readTemp - 0.25) + tempCount;
gbeardall 0:2f78e3dca55d 52 pc_ds18S20.traceOut("Temperature: %f \r\n", realTemp); // enhanced resolution value
gbeardall 0:2f78e3dca55d 53
gbeardall 0:2f78e3dca55d 54 return realTemp;
gbeardall 0:2f78e3dca55d 55 }