Wim De Roeve / DS18B20

OneWire Temperature library for interfacing DS18B20

Dependents:   DallasTemperature project1

DS18B20.cpp@0:ad90c2e86a63, 2011-04-17 (annotated)

Committer:
Wimpie
Date:
Sun Apr 17 17:27:20 2011 +0000
Revision:
0:ad90c2e86a63
improved 1W search function

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Wimpie 0:ad90c2e86a63 1 /*
Wimpie 0:ad90c2e86a63 2 * DS18B20. Maxim DS18B20 One-Wire Thermometer.
Wimpie 0:ad90c2e86a63 3 * Uses the OneWireCRC library.
Wimpie 0:ad90c2e86a63 4 *
Wimpie 0:ad90c2e86a63 5 * Copyright (C) <2010> Petras Saduikis <petras@petras.co.uk>
Wimpie 0:ad90c2e86a63 6 *
Wimpie 0:ad90c2e86a63 7 * This file is part of OneWireThermometer.
Wimpie 0:ad90c2e86a63 8 *
Wimpie 0:ad90c2e86a63 9 * OneWireThermometer is free software: you can redistribute it and/or modify
Wimpie 0:ad90c2e86a63 10 * it under the terms of the GNU General Public License as published by
Wimpie 0:ad90c2e86a63 11 * the Free Software Foundation, either version 3 of the License, or
Wimpie 0:ad90c2e86a63 12 * (at your option) any later version.
Wimpie 0:ad90c2e86a63 13 *
Wimpie 0:ad90c2e86a63 14 * OneWireThermometer is distributed in the hope that it will be useful,
Wimpie 0:ad90c2e86a63 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
Wimpie 0:ad90c2e86a63 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
Wimpie 0:ad90c2e86a63 17 * GNU General Public License for more details.
Wimpie 0:ad90c2e86a63 18 *
Wimpie 0:ad90c2e86a63 19 * You should have received a copy of the GNU General Public License
Wimpie 0:ad90c2e86a63 20 * along with OneWireThermometer. If not, see <http://www.gnu.org/licenses/>.
Wimpie 0:ad90c2e86a63 21 */
Wimpie 0:ad90c2e86a63 22
Wimpie 0:ad90c2e86a63 23 #include "DS18B20.h"
Wimpie 0:ad90c2e86a63 24 #include "DebugTrace.h"
Wimpie 0:ad90c2e86a63 25
Wimpie 0:ad90c2e86a63 26 DebugTrace pc_ds18B20(OFF, TO_SERIAL);
Wimpie 0:ad90c2e86a63 27
Wimpie 0:ad90c2e86a63 28 DS18B20::DS18B20(PinName pin,bool crcOn, bool useAddr, bool parasitic, unsigned char *Address) :
Wimpie 0:ad90c2e86a63 29 OneWireThermometer(pin, crcOn, useAddr, parasitic, DS18B20_ID, Address) {
Wimpie 0:ad90c2e86a63 30 }
Wimpie 0:ad90c2e86a63 31
Wimpie 0:ad90c2e86a63 32 void DS18B20::setResolution(eResolution resln) {
Wimpie 0:ad90c2e86a63 33 // as the write to the configuration register involves a write to the
Wimpie 0:ad90c2e86a63 34 // high and low alarm bytes, need to read these registers first
Wimpie 0:ad90c2e86a63 35 // and copy them back on the write
Wimpie 0:ad90c2e86a63 36
Wimpie 0:ad90c2e86a63 37 BYTE read_data[THERMOM_SCRATCHPAD_SIZE];
Wimpie 0:ad90c2e86a63 38 BYTE write_data[ALARM_CONFIG_SIZE];
Wimpie 0:ad90c2e86a63 39
Wimpie 0:ad90c2e86a63 40 if (readAndValidateData(read_data)) {
Wimpie 0:ad90c2e86a63 41 // copy alarm and config data to write data
Wimpie 0:ad90c2e86a63 42 for (int k = 2; k < 5; k++) {
Wimpie 0:ad90c2e86a63 43 write_data[k - 2] = read_data[k];
Wimpie 0:ad90c2e86a63 44 }
Wimpie 0:ad90c2e86a63 45 int config = write_data[2];
Wimpie 0:ad90c2e86a63 46 config &= 0x9F;
Wimpie 0:ad90c2e86a63 47 config ^= (resln << 5);
Wimpie 0:ad90c2e86a63 48 write_data[2] = config;
Wimpie 0:ad90c2e86a63 49
Wimpie 0:ad90c2e86a63 50 resetAndAddress();
Wimpie 0:ad90c2e86a63 51 oneWire.writeByte(DS18X20_WRITESCRATCH);
Wimpie 0:ad90c2e86a63 52 for (int k = 0; k < 3; k++) {
Wimpie 0:ad90c2e86a63 53 oneWire.writeByte(write_data[k]);
Wimpie 0:ad90c2e86a63 54 }
Wimpie 0:ad90c2e86a63 55
Wimpie 0:ad90c2e86a63 56 // remember it so we can use the correct delay in reading the temperature
Wimpie 0:ad90c2e86a63 57 // for parasitic power
Wimpie 0:ad90c2e86a63 58 _resolution = resln;
Wimpie 0:ad90c2e86a63 59 }
Wimpie 0:ad90c2e86a63 60 }
Wimpie 0:ad90c2e86a63 61
Wimpie 0:ad90c2e86a63 62 float DS18B20::calculateTemperature(BYTE* data) {
Wimpie 0:ad90c2e86a63 63 bool signBit = false;
Wimpie 0:ad90c2e86a63 64 if (data[TEMPERATURE_MSB] & 0x80) signBit = true;
Wimpie 0:ad90c2e86a63 65
Wimpie 0:ad90c2e86a63 66 int read_temp = (data[TEMPERATURE_MSB] << 8) + data[TEMPERATURE_LSB];
Wimpie 0:ad90c2e86a63 67 if (signBit) {
Wimpie 0:ad90c2e86a63 68 read_temp = (read_temp ^ 0xFFFF) + 1; // two's complement
Wimpie 0:ad90c2e86a63 69 read_temp *= -1;
Wimpie 0:ad90c2e86a63 70 }
Wimpie 0:ad90c2e86a63 71
Wimpie 0:ad90c2e86a63 72 int resolution = (data[CONFIG_REG_BYTE] & 0x60) >> 5; // mask off bits 6,5 and move to 1,0
Wimpie 0:ad90c2e86a63 73 switch (resolution) {
Wimpie 0:ad90c2e86a63 74 case nineBit: // 0.5 deg C increments
Wimpie 0:ad90c2e86a63 75 read_temp &= 0xFFF8; // bits 2,1,0 are undefined
Wimpie 0:ad90c2e86a63 76 pc_ds18B20.traceOut("9 bit resolution ...\r\n");
Wimpie 0:ad90c2e86a63 77 break;
Wimpie 0:ad90c2e86a63 78 case tenBit: // 0.25 deg C increments
Wimpie 0:ad90c2e86a63 79 read_temp &= 0xFFFC; // bits 1,0 are undefined
Wimpie 0:ad90c2e86a63 80 pc_ds18B20.traceOut("10 bit resolution ...\r\n");
Wimpie 0:ad90c2e86a63 81 break;
Wimpie 0:ad90c2e86a63 82 case elevenBit: // 0.125 deg C increments
Wimpie 0:ad90c2e86a63 83 read_temp &= 0xFFFE; // bit 0 is undefined
Wimpie 0:ad90c2e86a63 84 pc_ds18B20.traceOut("11 bit resolution ...\r\n");
Wimpie 0:ad90c2e86a63 85 break;
Wimpie 0:ad90c2e86a63 86 case twelveBit: // 0.0625 deg C increments
Wimpie 0:ad90c2e86a63 87 pc_ds18B20.traceOut("12 bit resolution ...\r\n");
Wimpie 0:ad90c2e86a63 88 break;
Wimpie 0:ad90c2e86a63 89 }
Wimpie 0:ad90c2e86a63 90 float realTemp = (float)read_temp/16 ;
Wimpie 0:ad90c2e86a63 91
Wimpie 0:ad90c2e86a63 92 pc_ds18B20.traceOut("TEMP_READ/REAL TEMP: %f \r\n", realTemp);
Wimpie 0:ad90c2e86a63 93
Wimpie 0:ad90c2e86a63 94 return realTemp;
Wimpie 0:ad90c2e86a63 95 }