Thing Innovations / DHT

DHT library

Fork of DHT by Wim De Roeve

DHT.cpp@1:6d97d5338f91, 2016-08-21 (annotated)

Committer:
SomeRandomBloke
Date:
Sun Aug 21 17:48:16 2016 +0000
Revision:
1:6d97d5338f91
Parent:
0:9b5b3200688f 
First

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
SomeRandomBloke 1:6d97d5338f91 35 //extern Serial pc;
SomeRandomBloke 1:6d97d5338f91 36 // was 41
SomeRandomBloke 1:6d97d5338f91 37 #define DHT_DATA_BIT_COUNT 40
Wimpie 0:9b5b3200688f 38
Wimpie 0:9b5b3200688f 39 DHT::DHT(PinName pin,int DHTtype) {
Wimpie 0:9b5b3200688f 40 _pin = pin;
Wimpie 0:9b5b3200688f 41 _DHTtype = DHTtype;
Wimpie 0:9b5b3200688f 42 _firsttime=true;
Wimpie 0:9b5b3200688f 43 }
Wimpie 0:9b5b3200688f 44
Wimpie 0:9b5b3200688f 45 DHT::~DHT() {
Wimpie 0:9b5b3200688f 46 }
Wimpie 0:9b5b3200688f 47
Wimpie 0:9b5b3200688f 48 int DHT::readData() {
Wimpie 0:9b5b3200688f 49 int i, j, retryCount,b;
Wimpie 0:9b5b3200688f 50 unsigned int bitTimes[DHT_DATA_BIT_COUNT];
Wimpie 0:9b5b3200688f 51
Wimpie 0:9b5b3200688f 52 eError err = ERROR_NONE;
Wimpie 0:9b5b3200688f 53 time_t currentTime = time(NULL);
Wimpie 0:9b5b3200688f 54
Wimpie 0:9b5b3200688f 55 DigitalInOut DHT_io(_pin);
Wimpie 0:9b5b3200688f 56
Wimpie 0:9b5b3200688f 57 for (i = 0; i < DHT_DATA_BIT_COUNT; i++) {
Wimpie 0:9b5b3200688f 58 bitTimes[i] = 0;
Wimpie 0:9b5b3200688f 59 }
Wimpie 0:9b5b3200688f 60
Wimpie 0:9b5b3200688f 61 if (!_firsttime) {
Wimpie 0:9b5b3200688f 62 if (int(currentTime - _lastReadTime) < 2) {
Wimpie 0:9b5b3200688f 63 err = ERROR_NO_PATIENCE;
Wimpie 0:9b5b3200688f 64 return err;
Wimpie 0:9b5b3200688f 65 }
Wimpie 0:9b5b3200688f 66 } else {
Wimpie 0:9b5b3200688f 67 _firsttime=false;
Wimpie 0:9b5b3200688f 68 _lastReadTime=currentTime;
Wimpie 0:9b5b3200688f 69 }
Wimpie 0:9b5b3200688f 70 retryCount = 0;
Wimpie 0:9b5b3200688f 71
Wimpie 0:9b5b3200688f 72 do {
Wimpie 0:9b5b3200688f 73 if (retryCount > 125) {
Wimpie 0:9b5b3200688f 74 err = BUS_BUSY;
Wimpie 0:9b5b3200688f 75 return err;
Wimpie 0:9b5b3200688f 76 }
Wimpie 0:9b5b3200688f 77 retryCount ++;
Wimpie 0:9b5b3200688f 78 wait_us(2);
Wimpie 0:9b5b3200688f 79 } while ((DHT_io==0));
Wimpie 0:9b5b3200688f 80
Wimpie 0:9b5b3200688f 81
Wimpie 0:9b5b3200688f 82 DHT_io.output();
Wimpie 0:9b5b3200688f 83 DHT_io = 0;
Wimpie 0:9b5b3200688f 84 wait_ms(18);
Wimpie 0:9b5b3200688f 85 DHT_io = 1;
Wimpie 0:9b5b3200688f 86 wait_us(40);
Wimpie 0:9b5b3200688f 87 DHT_io.input();
Wimpie 0:9b5b3200688f 88
Wimpie 0:9b5b3200688f 89 retryCount = 0;
Wimpie 0:9b5b3200688f 90 do {
Wimpie 0:9b5b3200688f 91 if (retryCount > 40) {
Wimpie 0:9b5b3200688f 92 err = ERROR_NOT_PRESENT;
Wimpie 0:9b5b3200688f 93 return err;
Wimpie 0:9b5b3200688f 94 }
Wimpie 0:9b5b3200688f 95 retryCount++;
Wimpie 0:9b5b3200688f 96 wait_us(1);
Wimpie 0:9b5b3200688f 97 } while ((DHT_io==1));
Wimpie 0:9b5b3200688f 98
Wimpie 0:9b5b3200688f 99 if (err != ERROR_NONE) {
Wimpie 0:9b5b3200688f 100 return err;
Wimpie 0:9b5b3200688f 101 }
Wimpie 0:9b5b3200688f 102
Wimpie 0:9b5b3200688f 103 wait_us(80);
Wimpie 0:9b5b3200688f 104
Wimpie 0:9b5b3200688f 105 for (i = 0; i < 5; i++) {
Wimpie 0:9b5b3200688f 106 for (j = 0; j < 8; j++) {
Wimpie 0:9b5b3200688f 107
Wimpie 0:9b5b3200688f 108 retryCount = 0;
Wimpie 0:9b5b3200688f 109 do {
Wimpie 0:9b5b3200688f 110 if (retryCount > 75) {
Wimpie 0:9b5b3200688f 111 err = ERROR_DATA_TIMEOUT;
Wimpie 0:9b5b3200688f 112 return err;
Wimpie 0:9b5b3200688f 113 }
Wimpie 0:9b5b3200688f 114 retryCount++;
Wimpie 0:9b5b3200688f 115 wait_us(1);
Wimpie 0:9b5b3200688f 116 } while (DHT_io == 0);
Wimpie 0:9b5b3200688f 117 wait_us(40);
Wimpie 0:9b5b3200688f 118 bitTimes[i*8+j]=DHT_io;
Wimpie 0:9b5b3200688f 119
Wimpie 0:9b5b3200688f 120 int count = 0;
Wimpie 0:9b5b3200688f 121 while (DHT_io == 1 && count < 100) {
Wimpie 0:9b5b3200688f 122 wait_us(1);
Wimpie 0:9b5b3200688f 123 count++;
Wimpie 0:9b5b3200688f 124 }
Wimpie 0:9b5b3200688f 125 }
Wimpie 0:9b5b3200688f 126 }
Wimpie 0:9b5b3200688f 127 DHT_io.output();
Wimpie 0:9b5b3200688f 128 DHT_io = 1;
Wimpie 0:9b5b3200688f 129 for (i = 0; i < 5; i++) {
Wimpie 0:9b5b3200688f 130 b=0;
Wimpie 0:9b5b3200688f 131 for (j=0; j<8; j++) {
Wimpie 0:9b5b3200688f 132 if (bitTimes[i*8+j+1] > 0) {
Wimpie 0:9b5b3200688f 133 b |= ( 1 << (7-j));
Wimpie 0:9b5b3200688f 134 }
Wimpie 0:9b5b3200688f 135 }
Wimpie 0:9b5b3200688f 136 DHT_data[i]=b;
Wimpie 0:9b5b3200688f 137 }
Wimpie 0:9b5b3200688f 138
SomeRandomBloke 1:6d97d5338f91 139 if (DHT_data[4] == ((DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]) & 0xFF) ||
SomeRandomBloke 1:6d97d5338f91 140 DHT_data[4] == ((DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]-1) & 0xFF)) {
Wimpie 0:9b5b3200688f 141 _lastReadTime = currentTime;
Wimpie 0:9b5b3200688f 142 _lastTemperature=CalcTemperature();
Wimpie 0:9b5b3200688f 143 _lastHumidity=CalcHumidity();
Wimpie 0:9b5b3200688f 144
Wimpie 0:9b5b3200688f 145 } else {
SomeRandomBloke 1:6d97d5338f91 146 /*for( int i=0; i < 5; i++ ) {
SomeRandomBloke 1:6d97d5338f91 147 pc.printf("%02X ",DHT_data[i]);
SomeRandomBloke 1:6d97d5338f91 148 }
SomeRandomBloke 1:6d97d5338f91 149 pc.printf("\n");
SomeRandomBloke 1:6d97d5338f91 150 pc.printf("%04X\n",(DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]));
SomeRandomBloke 1:6d97d5338f91 151 */
Wimpie 0:9b5b3200688f 152 err = ERROR_CHECKSUM;
Wimpie 0:9b5b3200688f 153 }
Wimpie 0:9b5b3200688f 154
Wimpie 0:9b5b3200688f 155 return err;
Wimpie 0:9b5b3200688f 156
Wimpie 0:9b5b3200688f 157 }
Wimpie 0:9b5b3200688f 158
Wimpie 0:9b5b3200688f 159 float DHT::CalcTemperature() {
SomeRandomBloke 1:6d97d5338f91 160 float v;
Wimpie 0:9b5b3200688f 161
Wimpie 0:9b5b3200688f 162 switch (_DHTtype) {
Wimpie 0:9b5b3200688f 163 case DHT11:
Wimpie 0:9b5b3200688f 164 v = DHT_data[2];
SomeRandomBloke 1:6d97d5338f91 165 return v;
Wimpie 0:9b5b3200688f 166 case DHT22:
Wimpie 0:9b5b3200688f 167 v = DHT_data[2] & 0x7F;
Wimpie 0:9b5b3200688f 168 v *= 256;
Wimpie 0:9b5b3200688f 169 v += DHT_data[3];
Wimpie 0:9b5b3200688f 170 v /= 10;
Wimpie 0:9b5b3200688f 171 if (DHT_data[2] & 0x80)
Wimpie 0:9b5b3200688f 172 v *= -1;
SomeRandomBloke 1:6d97d5338f91 173 return v;
Wimpie 0:9b5b3200688f 174 }
Wimpie 0:9b5b3200688f 175 return 0;
Wimpie 0:9b5b3200688f 176 }
Wimpie 0:9b5b3200688f 177
Wimpie 0:9b5b3200688f 178 float DHT::ReadHumidity() {
Wimpie 0:9b5b3200688f 179 return _lastHumidity;
Wimpie 0:9b5b3200688f 180 }
Wimpie 0:9b5b3200688f 181
Wimpie 0:9b5b3200688f 182 float DHT::ConvertCelciustoFarenheit(float celsius) {
SomeRandomBloke 1:6d97d5338f91 183 return celsius * 9 / 5 + 32.0f;
Wimpie 0:9b5b3200688f 184 }
Wimpie 0:9b5b3200688f 185
Wimpie 0:9b5b3200688f 186 float DHT::ConvertCelciustoKelvin(float celsius) {
SomeRandomBloke 1:6d97d5338f91 187 return celsius + 273.15f;
Wimpie 0:9b5b3200688f 188 }
Wimpie 0:9b5b3200688f 189
Wimpie 0:9b5b3200688f 190 // dewPoint function NOAA
Wimpie 0:9b5b3200688f 191 // reference: http://wahiduddin.net/calc/density_algorithms.htm
Wimpie 0:9b5b3200688f 192 float DHT::CalcdewPoint(float celsius, float humidity) {
SomeRandomBloke 1:6d97d5338f91 193 float A0= 373.15f/(273.15f + celsius);
SomeRandomBloke 1:6d97d5338f91 194 float SUM = -7.90298f * (A0-1);
SomeRandomBloke 1:6d97d5338f91 195 SUM += 5.02808f * log10(A0);
SomeRandomBloke 1:6d97d5338f91 196 SUM += -1.3816e-7 * (pow(10, (11.344f*(1-1/A0)))-1) ;
SomeRandomBloke 1:6d97d5338f91 197 SUM += 8.1328e-3f * (pow(10,(-3.49149f*(A0-1.0f)))-1) ;
Wimpie 0:9b5b3200688f 198 SUM += log10(1013.246);
Wimpie 0:9b5b3200688f 199 float VP = pow(10, SUM-3) * humidity;
SomeRandomBloke 1:6d97d5338f91 200 float T = log(VP/0.61078f); // temp var
SomeRandomBloke 1:6d97d5338f91 201 return (241.88f * T) / (17.558f-T);
Wimpie 0:9b5b3200688f 202 }
Wimpie 0:9b5b3200688f 203
Wimpie 0:9b5b3200688f 204 // delta max = 0.6544 wrt dewPoint()
Wimpie 0:9b5b3200688f 205 // 5x faster than dewPoint()
Wimpie 0:9b5b3200688f 206 // reference: http://en.wikipedia.org/wiki/Dew_point
Wimpie 0:9b5b3200688f 207 float DHT::CalcdewPointFast(float celsius, float humidity)
Wimpie 0:9b5b3200688f 208 {
Wimpie 0:9b5b3200688f 209 float a = 17.271;
Wimpie 0:9b5b3200688f 210 float b = 237.7;
Wimpie 0:9b5b3200688f 211 float temp = (a * celsius) / (b + celsius) + log(humidity/100);
Wimpie 0:9b5b3200688f 212 float Td = (b * temp) / (a - temp);
Wimpie 0:9b5b3200688f 213 return Td;
Wimpie 0:9b5b3200688f 214 }
Wimpie 0:9b5b3200688f 215
Wimpie 0:9b5b3200688f 216 float DHT::ReadTemperature(eScale Scale) {
Wimpie 0:9b5b3200688f 217 if (Scale == FARENHEIT)
Wimpie 0:9b5b3200688f 218 return ConvertCelciustoFarenheit(_lastTemperature);
Wimpie 0:9b5b3200688f 219 else if (Scale == KELVIN)
Wimpie 0:9b5b3200688f 220 return ConvertCelciustoKelvin(_lastTemperature);
Wimpie 0:9b5b3200688f 221 else
Wimpie 0:9b5b3200688f 222 return _lastTemperature;
Wimpie 0:9b5b3200688f 223 }
Wimpie 0:9b5b3200688f 224
Wimpie 0:9b5b3200688f 225 float DHT::CalcHumidity() {
SomeRandomBloke 1:6d97d5338f91 226 float v;
Wimpie 0:9b5b3200688f 227
Wimpie 0:9b5b3200688f 228 switch (_DHTtype) {
Wimpie 0:9b5b3200688f 229 case DHT11:
Wimpie 0:9b5b3200688f 230 v = DHT_data[0];
SomeRandomBloke 1:6d97d5338f91 231 return v;
Wimpie 0:9b5b3200688f 232 case DHT22:
Wimpie 0:9b5b3200688f 233 v = DHT_data[0];
Wimpie 0:9b5b3200688f 234 v *= 256;
Wimpie 0:9b5b3200688f 235 v += DHT_data[1];
Wimpie 0:9b5b3200688f 236 v /= 10;
SomeRandomBloke 1:6d97d5338f91 237 return v;
Wimpie 0:9b5b3200688f 238 }
Wimpie 0:9b5b3200688f 239 return 0;
Wimpie 0:9b5b3200688f 240 }
Wimpie 0:9b5b3200688f 241
Wimpie 0:9b5b3200688f 242