ajeet prajapati / DHT

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Dependents:   DHT11-HelloWorld1 DHT11-HelloWorld1 STMNucleoF401RE_ExampleCode_08_DHT11

Fork of DHT by Components

DHT.cpp@1:25c96950b6ed, 2013-07-24 (annotated)

Committer:
yihui
Date:
Wed Jul 24 06:59:28 2013 +0000
Revision:
1:25c96950b6ed
Parent:
0:9b5b3200688f
Child:
2:df22ddf10d75
Seeeduino Arch + Grove - OLED 128x64 + Grove - Temperature & Humidity Sensor Pro to sense the environment

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Wimpie 0:9b5b3200688f 1 /*
Wimpie 0:9b5b3200688f 2 * DHT Library for Digital-output Humidity and Temperature sensors
Wimpie 0:9b5b3200688f 3 *
Wimpie 0:9b5b3200688f 4 * Works with DHT11, DHT22
Wimpie 0:9b5b3200688f 5 * SEN11301P, Grove - Temperature&Humidity Sensor (Seeed Studio)
Wimpie 0:9b5b3200688f 6 * SEN51035P, Grove - Temperature&Humidity Sensor Pro (Seeed Studio)
Wimpie 0:9b5b3200688f 7 * AM2302 , temperature-humidity sensor
Wimpie 0:9b5b3200688f 8 * HM2303 , Digital-output humidity and temperature sensor
Wimpie 0:9b5b3200688f 9 *
Wimpie 0:9b5b3200688f 10 * Copyright (C) Wim De Roeve
Wimpie 0:9b5b3200688f 11 * based on DHT22 sensor library by HO WING KIT
Wimpie 0:9b5b3200688f 12 * Arduino DHT11 library
Wimpie 0:9b5b3200688f 13 *
Wimpie 0:9b5b3200688f 14 * Permission is hereby granted, free of charge, to any person obtaining a copy
Wimpie 0:9b5b3200688f 15 * of this software and associated documnetation files (the "Software"), to deal
Wimpie 0:9b5b3200688f 16 * in the Software without restriction, including without limitation the rights
Wimpie 0:9b5b3200688f 17 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
Wimpie 0:9b5b3200688f 18 * copies of the Software, and to permit persons to whom the Software is
Wimpie 0:9b5b3200688f 19 * furished to do so, subject to the following conditions:
Wimpie 0:9b5b3200688f 20 *
Wimpie 0:9b5b3200688f 21 * The above copyright notice and this permission notice shall be included in
Wimpie 0:9b5b3200688f 22 * all copies or substantial portions of the Software.
Wimpie 0:9b5b3200688f 23 *
Wimpie 0:9b5b3200688f 24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
Wimpie 0:9b5b3200688f 25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
Wimpie 0:9b5b3200688f 26 * FITNESS OR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
Wimpie 0:9b5b3200688f 27 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
Wimpie 0:9b5b3200688f 28 * LIABILITY WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
Wimpie 0:9b5b3200688f 29 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
Wimpie 0:9b5b3200688f 30 * THE SOFTWARE.
Wimpie 0:9b5b3200688f 31 */
Wimpie 0:9b5b3200688f 32
Wimpie 0:9b5b3200688f 33 #include "DHT.h"
Wimpie 0:9b5b3200688f 34
Wimpie 0:9b5b3200688f 35 #define DHT_DATA_BIT_COUNT 41
Wimpie 0:9b5b3200688f 36
Wimpie 0:9b5b3200688f 37 DHT::DHT(PinName pin,int DHTtype) {
Wimpie 0:9b5b3200688f 38 _pin = pin;
Wimpie 0:9b5b3200688f 39 _DHTtype = DHTtype;
Wimpie 0:9b5b3200688f 40 _firsttime=true;
Wimpie 0:9b5b3200688f 41 }
Wimpie 0:9b5b3200688f 42
Wimpie 0:9b5b3200688f 43 DHT::~DHT() {
Wimpie 0:9b5b3200688f 44 }
Wimpie 0:9b5b3200688f 45
Wimpie 0:9b5b3200688f 46 int DHT::readData() {
Wimpie 0:9b5b3200688f 47 int i, j, retryCount,b;
Wimpie 0:9b5b3200688f 48 unsigned int bitTimes[DHT_DATA_BIT_COUNT];
Wimpie 0:9b5b3200688f 49
Wimpie 0:9b5b3200688f 50 eError err = ERROR_NONE;
Wimpie 0:9b5b3200688f 51 time_t currentTime = time(NULL);
Wimpie 0:9b5b3200688f 52
Wimpie 0:9b5b3200688f 53 DigitalInOut DHT_io(_pin);
Wimpie 0:9b5b3200688f 54
Wimpie 0:9b5b3200688f 55 for (i = 0; i < DHT_DATA_BIT_COUNT; i++) {
Wimpie 0:9b5b3200688f 56 bitTimes[i] = 0;
Wimpie 0:9b5b3200688f 57 }
yihui 1:25c96950b6ed 58 #if 0
Wimpie 0:9b5b3200688f 59 if (!_firsttime) {
Wimpie 0:9b5b3200688f 60 if (int(currentTime - _lastReadTime) < 2) {
Wimpie 0:9b5b3200688f 61 err = ERROR_NO_PATIENCE;
Wimpie 0:9b5b3200688f 62 return err;
Wimpie 0:9b5b3200688f 63 }
Wimpie 0:9b5b3200688f 64 } else {
Wimpie 0:9b5b3200688f 65 _firsttime=false;
Wimpie 0:9b5b3200688f 66 _lastReadTime=currentTime;
Wimpie 0:9b5b3200688f 67 }
yihui 1:25c96950b6ed 68 #endif
Wimpie 0:9b5b3200688f 69 retryCount = 0;
Wimpie 0:9b5b3200688f 70
Wimpie 0:9b5b3200688f 71 do {
Wimpie 0:9b5b3200688f 72 if (retryCount > 125) {
Wimpie 0:9b5b3200688f 73 err = BUS_BUSY;
Wimpie 0:9b5b3200688f 74 return err;
Wimpie 0:9b5b3200688f 75 }
Wimpie 0:9b5b3200688f 76 retryCount ++;
Wimpie 0:9b5b3200688f 77 wait_us(2);
Wimpie 0:9b5b3200688f 78 } while ((DHT_io==0));
Wimpie 0:9b5b3200688f 79
Wimpie 0:9b5b3200688f 80
Wimpie 0:9b5b3200688f 81 DHT_io.output();
Wimpie 0:9b5b3200688f 82 DHT_io = 0;
Wimpie 0:9b5b3200688f 83 wait_ms(18);
Wimpie 0:9b5b3200688f 84 DHT_io = 1;
Wimpie 0:9b5b3200688f 85 wait_us(40);
Wimpie 0:9b5b3200688f 86 DHT_io.input();
Wimpie 0:9b5b3200688f 87
Wimpie 0:9b5b3200688f 88 retryCount = 0;
Wimpie 0:9b5b3200688f 89 do {
Wimpie 0:9b5b3200688f 90 if (retryCount > 40) {
Wimpie 0:9b5b3200688f 91 err = ERROR_NOT_PRESENT;
Wimpie 0:9b5b3200688f 92 return err;
Wimpie 0:9b5b3200688f 93 }
Wimpie 0:9b5b3200688f 94 retryCount++;
Wimpie 0:9b5b3200688f 95 wait_us(1);
Wimpie 0:9b5b3200688f 96 } while ((DHT_io==1));
Wimpie 0:9b5b3200688f 97
Wimpie 0:9b5b3200688f 98 if (err != ERROR_NONE) {
Wimpie 0:9b5b3200688f 99 return err;
Wimpie 0:9b5b3200688f 100 }
Wimpie 0:9b5b3200688f 101
Wimpie 0:9b5b3200688f 102 wait_us(80);
Wimpie 0:9b5b3200688f 103
Wimpie 0:9b5b3200688f 104 for (i = 0; i < 5; i++) {
Wimpie 0:9b5b3200688f 105 for (j = 0; j < 8; j++) {
Wimpie 0:9b5b3200688f 106
Wimpie 0:9b5b3200688f 107 retryCount = 0;
Wimpie 0:9b5b3200688f 108 do {
Wimpie 0:9b5b3200688f 109 if (retryCount > 75) {
Wimpie 0:9b5b3200688f 110 err = ERROR_DATA_TIMEOUT;
Wimpie 0:9b5b3200688f 111 return err;
Wimpie 0:9b5b3200688f 112 }
Wimpie 0:9b5b3200688f 113 retryCount++;
Wimpie 0:9b5b3200688f 114 wait_us(1);
Wimpie 0:9b5b3200688f 115 } while (DHT_io == 0);
Wimpie 0:9b5b3200688f 116 wait_us(40);
Wimpie 0:9b5b3200688f 117 bitTimes[i*8+j]=DHT_io;
Wimpie 0:9b5b3200688f 118
Wimpie 0:9b5b3200688f 119 int count = 0;
Wimpie 0:9b5b3200688f 120 while (DHT_io == 1 && count < 100) {
Wimpie 0:9b5b3200688f 121 wait_us(1);
Wimpie 0:9b5b3200688f 122 count++;
Wimpie 0:9b5b3200688f 123 }
Wimpie 0:9b5b3200688f 124 }
Wimpie 0:9b5b3200688f 125 }
Wimpie 0:9b5b3200688f 126 DHT_io.output();
Wimpie 0:9b5b3200688f 127 DHT_io = 1;
Wimpie 0:9b5b3200688f 128 for (i = 0; i < 5; i++) {
Wimpie 0:9b5b3200688f 129 b=0;
Wimpie 0:9b5b3200688f 130 for (j=0; j<8; j++) {
Wimpie 0:9b5b3200688f 131 if (bitTimes[i*8+j+1] > 0) {
Wimpie 0:9b5b3200688f 132 b |= ( 1 << (7-j));
Wimpie 0:9b5b3200688f 133 }
Wimpie 0:9b5b3200688f 134 }
Wimpie 0:9b5b3200688f 135 DHT_data[i]=b;
Wimpie 0:9b5b3200688f 136 }
Wimpie 0:9b5b3200688f 137
Wimpie 0:9b5b3200688f 138 if (DHT_data[4] == ((DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]) & 0xFF)) {
Wimpie 0:9b5b3200688f 139 _lastReadTime = currentTime;
Wimpie 0:9b5b3200688f 140 _lastTemperature=CalcTemperature();
Wimpie 0:9b5b3200688f 141 _lastHumidity=CalcHumidity();
Wimpie 0:9b5b3200688f 142
Wimpie 0:9b5b3200688f 143 } else {
Wimpie 0:9b5b3200688f 144 err = ERROR_CHECKSUM;
Wimpie 0:9b5b3200688f 145 }
Wimpie 0:9b5b3200688f 146
Wimpie 0:9b5b3200688f 147 return err;
Wimpie 0:9b5b3200688f 148
Wimpie 0:9b5b3200688f 149 }
Wimpie 0:9b5b3200688f 150
Wimpie 0:9b5b3200688f 151 float DHT::CalcTemperature() {
Wimpie 0:9b5b3200688f 152 int v;
Wimpie 0:9b5b3200688f 153
Wimpie 0:9b5b3200688f 154 switch (_DHTtype) {
Wimpie 0:9b5b3200688f 155 case DHT11:
Wimpie 0:9b5b3200688f 156 v = DHT_data[2];
Wimpie 0:9b5b3200688f 157 return float(v);
Wimpie 0:9b5b3200688f 158 case DHT22:
Wimpie 0:9b5b3200688f 159 v = DHT_data[2] & 0x7F;
Wimpie 0:9b5b3200688f 160 v *= 256;
Wimpie 0:9b5b3200688f 161 v += DHT_data[3];
Wimpie 0:9b5b3200688f 162 v /= 10;
Wimpie 0:9b5b3200688f 163 if (DHT_data[2] & 0x80)
Wimpie 0:9b5b3200688f 164 v *= -1;
Wimpie 0:9b5b3200688f 165 return float(v);
Wimpie 0:9b5b3200688f 166 }
Wimpie 0:9b5b3200688f 167 return 0;
Wimpie 0:9b5b3200688f 168 }
Wimpie 0:9b5b3200688f 169
Wimpie 0:9b5b3200688f 170 float DHT::ReadHumidity() {
Wimpie 0:9b5b3200688f 171 return _lastHumidity;
Wimpie 0:9b5b3200688f 172 }
Wimpie 0:9b5b3200688f 173
Wimpie 0:9b5b3200688f 174 float DHT::ConvertCelciustoFarenheit(float celsius) {
Wimpie 0:9b5b3200688f 175 return celsius * 9 / 5 + 32;
Wimpie 0:9b5b3200688f 176 }
Wimpie 0:9b5b3200688f 177
Wimpie 0:9b5b3200688f 178 float DHT::ConvertCelciustoKelvin(float celsius) {
Wimpie 0:9b5b3200688f 179 return celsius + 273.15;
Wimpie 0:9b5b3200688f 180 }
Wimpie 0:9b5b3200688f 181
Wimpie 0:9b5b3200688f 182 // dewPoint function NOAA
Wimpie 0:9b5b3200688f 183 // reference: http://wahiduddin.net/calc/density_algorithms.htm
Wimpie 0:9b5b3200688f 184 float DHT::CalcdewPoint(float celsius, float humidity) {
Wimpie 0:9b5b3200688f 185 float A0= 373.15/(273.15 + celsius);
Wimpie 0:9b5b3200688f 186 float SUM = -7.90298 * (A0-1);
Wimpie 0:9b5b3200688f 187 SUM += 5.02808 * log10(A0);
Wimpie 0:9b5b3200688f 188 SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
Wimpie 0:9b5b3200688f 189 SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
Wimpie 0:9b5b3200688f 190 SUM += log10(1013.246);
Wimpie 0:9b5b3200688f 191 float VP = pow(10, SUM-3) * humidity;
Wimpie 0:9b5b3200688f 192 float T = log(VP/0.61078); // temp var
Wimpie 0:9b5b3200688f 193 return (241.88 * T) / (17.558-T);
Wimpie 0:9b5b3200688f 194 }
Wimpie 0:9b5b3200688f 195
Wimpie 0:9b5b3200688f 196 // delta max = 0.6544 wrt dewPoint()
Wimpie 0:9b5b3200688f 197 // 5x faster than dewPoint()
Wimpie 0:9b5b3200688f 198 // reference: http://en.wikipedia.org/wiki/Dew_point
Wimpie 0:9b5b3200688f 199 float DHT::CalcdewPointFast(float celsius, float humidity)
Wimpie 0:9b5b3200688f 200 {
Wimpie 0:9b5b3200688f 201 float a = 17.271;
Wimpie 0:9b5b3200688f 202 float b = 237.7;
Wimpie 0:9b5b3200688f 203 float temp = (a * celsius) / (b + celsius) + log(humidity/100);
Wimpie 0:9b5b3200688f 204 float Td = (b * temp) / (a - temp);
Wimpie 0:9b5b3200688f 205 return Td;
Wimpie 0:9b5b3200688f 206 }
Wimpie 0:9b5b3200688f 207
Wimpie 0:9b5b3200688f 208 float DHT::ReadTemperature(eScale Scale) {
Wimpie 0:9b5b3200688f 209 if (Scale == FARENHEIT)
Wimpie 0:9b5b3200688f 210 return ConvertCelciustoFarenheit(_lastTemperature);
Wimpie 0:9b5b3200688f 211 else if (Scale == KELVIN)
Wimpie 0:9b5b3200688f 212 return ConvertCelciustoKelvin(_lastTemperature);
Wimpie 0:9b5b3200688f 213 else
Wimpie 0:9b5b3200688f 214 return _lastTemperature;
Wimpie 0:9b5b3200688f 215 }
Wimpie 0:9b5b3200688f 216
Wimpie 0:9b5b3200688f 217 float DHT::CalcHumidity() {
Wimpie 0:9b5b3200688f 218 int v;
Wimpie 0:9b5b3200688f 219
Wimpie 0:9b5b3200688f 220 switch (_DHTtype) {
Wimpie 0:9b5b3200688f 221 case DHT11:
Wimpie 0:9b5b3200688f 222 v = DHT_data[0];
Wimpie 0:9b5b3200688f 223 return float(v);
Wimpie 0:9b5b3200688f 224 case DHT22:
Wimpie 0:9b5b3200688f 225 v = DHT_data[0];
Wimpie 0:9b5b3200688f 226 v *= 256;
Wimpie 0:9b5b3200688f 227 v += DHT_data[1];
Wimpie 0:9b5b3200688f 228 v /= 10;
Wimpie 0:9b5b3200688f 229 return float(v);
Wimpie 0:9b5b3200688f 230 }
Wimpie 0:9b5b3200688f 231 return 0;
Wimpie 0:9b5b3200688f 232 }
Wimpie 0:9b5b3200688f 233
Wimpie 0:9b5b3200688f 234