jack zen / DS18B20

DS18B20

Dependents:   DS1820_HelloWorld

DS18B20.cpp@0:cf42e1112753, 2017-09-06 (annotated)

Committer:
jack__zen
Date:
Wed Sep 06 05:34:51 2017 +0000
Revision:
0:cf42e1112753
ds18b20

Who changed what in which revision?

UserRevisionLine numberNew contents of line
jack__zen 0:cf42e1112753 1 /*
jack__zen 0:cf42e1112753 2 * DS18B20. Maxim DS18B20 One-Wire Thermometer.
jack__zen 0:cf42e1112753 3 * Uses the OneWireCRC library.
jack__zen 0:cf42e1112753 4 *
jack__zen 0:cf42e1112753 5 * Copyright (C) <2010> Petras Saduikis <petras@petras.co.uk>
jack__zen 0:cf42e1112753 6 *
jack__zen 0:cf42e1112753 7 * This file is part of OneWireThermometer.
jack__zen 0:cf42e1112753 8 *
jack__zen 0:cf42e1112753 9 * OneWireThermometer is free software: you can redistribute it and/or modify
jack__zen 0:cf42e1112753 10 * it under the terms of the GNU General Public License as published by
jack__zen 0:cf42e1112753 11 * the Free Software Foundation, either version 3 of the License, or
jack__zen 0:cf42e1112753 12 * (at your option) any later version.
jack__zen 0:cf42e1112753 13 *
jack__zen 0:cf42e1112753 14 * OneWireThermometer is distributed in the hope that it will be useful,
jack__zen 0:cf42e1112753 15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
jack__zen 0:cf42e1112753 16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
jack__zen 0:cf42e1112753 17 * GNU General Public License for more details.
jack__zen 0:cf42e1112753 18 *
jack__zen 0:cf42e1112753 19 * You should have received a copy of the GNU General Public License
jack__zen 0:cf42e1112753 20 * along with OneWireThermometer. If not, see <http://www.gnu.org/licenses/>.
jack__zen 0:cf42e1112753 21 */
jack__zen 0:cf42e1112753 22
jack__zen 0:cf42e1112753 23 #include "DS18B20.h"
jack__zen 0:cf42e1112753 24 #include "DebugTrace.h"
jack__zen 0:cf42e1112753 25
jack__zen 0:cf42e1112753 26 DebugTrace pc_ds18B20(ON, TO_SERIAL);
jack__zen 0:cf42e1112753 27
jack__zen 0:cf42e1112753 28 DS18B20::DS18B20(bool crcOn, bool useAddr, bool parasitic, PinName pin) :
jack__zen 0:cf42e1112753 29 OneWireThermometer(crcOn, useAddr, parasitic, pin, DS18B20_ID)
jack__zen 0:cf42e1112753 30 {
jack__zen 0:cf42e1112753 31 }
jack__zen 0:cf42e1112753 32
jack__zen 0:cf42e1112753 33 void DS18B20::setResolution(eResolution resln)
jack__zen 0:cf42e1112753 34 {
jack__zen 0:cf42e1112753 35 // as the write to the configuration register involves a write to the
jack__zen 0:cf42e1112753 36 // high and low alarm bytes, need to read these registers first
jack__zen 0:cf42e1112753 37 // and copy them back on the write
jack__zen 0:cf42e1112753 38
jack__zen 0:cf42e1112753 39 BYTE read_data[THERMOM_SCRATCHPAD_SIZE];
jack__zen 0:cf42e1112753 40 BYTE write_data[ALARM_CONFIG_SIZE];
jack__zen 0:cf42e1112753 41
jack__zen 0:cf42e1112753 42 if (readAndValidateData(read_data))
jack__zen 0:cf42e1112753 43 {
jack__zen 0:cf42e1112753 44 // copy alarm and config data to write data
jack__zen 0:cf42e1112753 45 for (int k = 2; k < 5; k++)
jack__zen 0:cf42e1112753 46 {
jack__zen 0:cf42e1112753 47 write_data[k - 2] = read_data[k];
jack__zen 0:cf42e1112753 48 }
jack__zen 0:cf42e1112753 49 int config = write_data[2];
jack__zen 0:cf42e1112753 50 config &= 0x9F;
jack__zen 0:cf42e1112753 51 config ^= (resln << 5);
jack__zen 0:cf42e1112753 52 write_data[2] = config;
jack__zen 0:cf42e1112753 53
jack__zen 0:cf42e1112753 54 resetAndAddress();
jack__zen 0:cf42e1112753 55 oneWire.writeByte(WRITESCRATCH);
jack__zen 0:cf42e1112753 56 for (int k = 0; k < 3; k++)
jack__zen 0:cf42e1112753 57 {
jack__zen 0:cf42e1112753 58 oneWire.writeByte(write_data[k]);
jack__zen 0:cf42e1112753 59 }
jack__zen 0:cf42e1112753 60
jack__zen 0:cf42e1112753 61 // remember it so we can use the correct delay in reading the temperature
jack__zen 0:cf42e1112753 62 // for parasitic power
jack__zen 0:cf42e1112753 63 resolution = resln;
jack__zen 0:cf42e1112753 64 }
jack__zen 0:cf42e1112753 65 }
jack__zen 0:cf42e1112753 66
jack__zen 0:cf42e1112753 67 float DS18B20::calculateTemperature(BYTE* data)
jack__zen 0:cf42e1112753 68 {
jack__zen 0:cf42e1112753 69 bool signBit = false;
jack__zen 0:cf42e1112753 70 if (data[TEMPERATURE_MSB] & 0x80) signBit = true;
jack__zen 0:cf42e1112753 71
jack__zen 0:cf42e1112753 72 int read_temp = (data[TEMPERATURE_MSB] << 8) + data[TEMPERATURE_LSB];
jack__zen 0:cf42e1112753 73 if (signBit)
jack__zen 0:cf42e1112753 74 {
jack__zen 0:cf42e1112753 75 read_temp = (read_temp ^ 0xFFFF) + 1; // two's complement
jack__zen 0:cf42e1112753 76 read_temp *= -1;
jack__zen 0:cf42e1112753 77 }
jack__zen 0:cf42e1112753 78
jack__zen 0:cf42e1112753 79 int resolution = (data[CONFIG_REG_BYTE] & 0x60) >> 5; // mask off bits 6,5 and move to 1,0
jack__zen 0:cf42e1112753 80 switch (resolution)
jack__zen 0:cf42e1112753 81 {
jack__zen 0:cf42e1112753 82 case nineBit: // 0.5 deg C increments
jack__zen 0:cf42e1112753 83 read_temp &= 0xFFF8; // bits 2,1,0 are undefined
jack__zen 0:cf42e1112753 84 pc_ds18B20.traceOut("9 bit resolution ...\r\n");
jack__zen 0:cf42e1112753 85 break;
jack__zen 0:cf42e1112753 86 case tenBit: // 0.25 deg C increments
jack__zen 0:cf42e1112753 87 read_temp &= 0xFFFC; // bits 1,0 are undefined
jack__zen 0:cf42e1112753 88 pc_ds18B20.traceOut("10 bit resolution ...\r\n");
jack__zen 0:cf42e1112753 89 break;
jack__zen 0:cf42e1112753 90 case elevenBit: // 0.125 deg C increments
jack__zen 0:cf42e1112753 91 read_temp &= 0xFFFE; // bit 0 is undefined
jack__zen 0:cf42e1112753 92 pc_ds18B20.traceOut("11 bit resolution ...\r\n");
jack__zen 0:cf42e1112753 93 break;
jack__zen 0:cf42e1112753 94 case twelveBit: // 0.0625 deg C increments
jack__zen 0:cf42e1112753 95 pc_ds18B20.traceOut("12 bit resolution ...\r\n");
jack__zen 0:cf42e1112753 96 break;
jack__zen 0:cf42e1112753 97 }
jack__zen 0:cf42e1112753 98 float realTemp = (float)read_temp/16 ;
jack__zen 0:cf42e1112753 99
jack__zen 0:cf42e1112753 100 pc_ds18B20.traceOut("TEMP_READ/REAL TEMP: %f \r\n", realTemp);
jack__zen 0:cf42e1112753 101
jack__zen 0:cf42e1112753 102 return realTemp;
jack__zen 0:cf42e1112753 103 }