Micah B / DHT

DHT

Fork of DHT by Wim De Roeve

DHT.cpp@1:42593954052a, 2015-02-25 (annotated)

Committer:
mbotkinl
Date:
Wed Feb 25 20:23:00 2015 +0000
Revision:
1:42593954052a
Parent:
0:9b5b3200688f 
Commented out some errors in DHT library

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"
mbotkinl 1:42593954052a 34 #define DHT_DATA_BIT_COUNT 41
mbotkinl 1:42593954052a 35 DigitalOut myled1(LED2);
Wimpie 0:9b5b3200688f 36
Wimpie 0:9b5b3200688f 37
Wimpie 0:9b5b3200688f 38 DHT::DHT(PinName pin,int DHTtype) {
Wimpie 0:9b5b3200688f 39 _pin = pin;
Wimpie 0:9b5b3200688f 40 _DHTtype = DHTtype;
Wimpie 0:9b5b3200688f 41 _firsttime=true;
Wimpie 0:9b5b3200688f 42 }
Wimpie 0:9b5b3200688f 43
Wimpie 0:9b5b3200688f 44 DHT::~DHT() {
Wimpie 0:9b5b3200688f 45 }
Wimpie 0:9b5b3200688f 46
Wimpie 0:9b5b3200688f 47 int DHT::readData() {
Wimpie 0:9b5b3200688f 48 int i, j, retryCount,b;
Wimpie 0:9b5b3200688f 49 unsigned int bitTimes[DHT_DATA_BIT_COUNT];
Wimpie 0:9b5b3200688f 50
mbotkinl 1:42593954052a 51
mbotkinl 1:42593954052a 52 //myled1=0;
Wimpie 0:9b5b3200688f 53 eError err = ERROR_NONE;
Wimpie 0:9b5b3200688f 54 time_t currentTime = time(NULL);
Wimpie 0:9b5b3200688f 55
Wimpie 0:9b5b3200688f 56 DigitalInOut DHT_io(_pin);
Wimpie 0:9b5b3200688f 57
Wimpie 0:9b5b3200688f 58 for (i = 0; i < DHT_DATA_BIT_COUNT; i++) {
Wimpie 0:9b5b3200688f 59 bitTimes[i] = 0;
Wimpie 0:9b5b3200688f 60 }
Wimpie 0:9b5b3200688f 61
mbotkinl 1:42593954052a 62 // if (!_firsttime) {
mbotkinl 1:42593954052a 63 // if (int(currentTime - _lastReadTime) < 2) {
mbotkinl 1:42593954052a 64 // err = ERROR_NO_PATIENCE;
mbotkinl 1:42593954052a 65 // return err;
mbotkinl 1:42593954052a 66 // }
mbotkinl 1:42593954052a 67 // } else {
mbotkinl 1:42593954052a 68 // _firsttime=false;
mbotkinl 1:42593954052a 69 // _lastReadTime=currentTime;
mbotkinl 1:42593954052a 70 // }
Wimpie 0:9b5b3200688f 71 retryCount = 0;
Wimpie 0:9b5b3200688f 72
Wimpie 0:9b5b3200688f 73 do {
Wimpie 0:9b5b3200688f 74 if (retryCount > 125) {
Wimpie 0:9b5b3200688f 75 err = BUS_BUSY;
Wimpie 0:9b5b3200688f 76 return err;
Wimpie 0:9b5b3200688f 77 }
Wimpie 0:9b5b3200688f 78 retryCount ++;
Wimpie 0:9b5b3200688f 79 wait_us(2);
Wimpie 0:9b5b3200688f 80 } while ((DHT_io==0));
Wimpie 0:9b5b3200688f 81
Wimpie 0:9b5b3200688f 82
Wimpie 0:9b5b3200688f 83 DHT_io.output();
Wimpie 0:9b5b3200688f 84 DHT_io = 0;
mbotkinl 1:42593954052a 85
mbotkinl 1:42593954052a 86
mbotkinl 1:42593954052a 87
mbotkinl 1:42593954052a 88 // wait(.1);
mbotkinl 1:42593954052a 89 // DHT_io=1;
mbotkinl 1:42593954052a 90 // wait(.1);
mbotkinl 1:42593954052a 91 // DHT_io=0;
mbotkinl 1:42593954052a 92 // return 0;
mbotkinl 1:42593954052a 93
mbotkinl 1:42593954052a 94
mbotkinl 1:42593954052a 95
mbotkinl 1:42593954052a 96
mbotkinl 1:42593954052a 97
mbotkinl 1:42593954052a 98
mbotkinl 1:42593954052a 99
Wimpie 0:9b5b3200688f 100 wait_ms(18);
Wimpie 0:9b5b3200688f 101 DHT_io = 1;
Wimpie 0:9b5b3200688f 102 wait_us(40);
Wimpie 0:9b5b3200688f 103 DHT_io.input();
Wimpie 0:9b5b3200688f 104
Wimpie 0:9b5b3200688f 105 retryCount = 0;
Wimpie 0:9b5b3200688f 106 do {
Wimpie 0:9b5b3200688f 107 if (retryCount > 40) {
Wimpie 0:9b5b3200688f 108 err = ERROR_NOT_PRESENT;
Wimpie 0:9b5b3200688f 109 return err;
Wimpie 0:9b5b3200688f 110 }
Wimpie 0:9b5b3200688f 111 retryCount++;
Wimpie 0:9b5b3200688f 112 wait_us(1);
Wimpie 0:9b5b3200688f 113 } while ((DHT_io==1));
Wimpie 0:9b5b3200688f 114
Wimpie 0:9b5b3200688f 115 if (err != ERROR_NONE) {
Wimpie 0:9b5b3200688f 116 return err;
Wimpie 0:9b5b3200688f 117 }
Wimpie 0:9b5b3200688f 118
Wimpie 0:9b5b3200688f 119 wait_us(80);
Wimpie 0:9b5b3200688f 120
Wimpie 0:9b5b3200688f 121 for (i = 0; i < 5; i++) {
Wimpie 0:9b5b3200688f 122 for (j = 0; j < 8; j++) {
Wimpie 0:9b5b3200688f 123
Wimpie 0:9b5b3200688f 124 retryCount = 0;
Wimpie 0:9b5b3200688f 125 do {
Wimpie 0:9b5b3200688f 126 if (retryCount > 75) {
Wimpie 0:9b5b3200688f 127 err = ERROR_DATA_TIMEOUT;
Wimpie 0:9b5b3200688f 128 return err;
Wimpie 0:9b5b3200688f 129 }
Wimpie 0:9b5b3200688f 130 retryCount++;
Wimpie 0:9b5b3200688f 131 wait_us(1);
Wimpie 0:9b5b3200688f 132 } while (DHT_io == 0);
Wimpie 0:9b5b3200688f 133 wait_us(40);
Wimpie 0:9b5b3200688f 134 bitTimes[i*8+j]=DHT_io;
Wimpie 0:9b5b3200688f 135
Wimpie 0:9b5b3200688f 136 int count = 0;
Wimpie 0:9b5b3200688f 137 while (DHT_io == 1 && count < 100) {
Wimpie 0:9b5b3200688f 138 wait_us(1);
Wimpie 0:9b5b3200688f 139 count++;
Wimpie 0:9b5b3200688f 140 }
Wimpie 0:9b5b3200688f 141 }
Wimpie 0:9b5b3200688f 142 }
Wimpie 0:9b5b3200688f 143 DHT_io.output();
Wimpie 0:9b5b3200688f 144 DHT_io = 1;
Wimpie 0:9b5b3200688f 145 for (i = 0; i < 5; i++) {
Wimpie 0:9b5b3200688f 146 b=0;
Wimpie 0:9b5b3200688f 147 for (j=0; j<8; j++) {
Wimpie 0:9b5b3200688f 148 if (bitTimes[i*8+j+1] > 0) {
Wimpie 0:9b5b3200688f 149 b |= ( 1 << (7-j));
Wimpie 0:9b5b3200688f 150 }
Wimpie 0:9b5b3200688f 151 }
Wimpie 0:9b5b3200688f 152 DHT_data[i]=b;
Wimpie 0:9b5b3200688f 153 }
Wimpie 0:9b5b3200688f 154
mbotkinl 1:42593954052a 155 if (DHT_data[4] == ((DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]) & 0xFF)) {
Wimpie 0:9b5b3200688f 156 _lastReadTime = currentTime;
Wimpie 0:9b5b3200688f 157 _lastTemperature=CalcTemperature();
Wimpie 0:9b5b3200688f 158 _lastHumidity=CalcHumidity();
Wimpie 0:9b5b3200688f 159
Wimpie 0:9b5b3200688f 160 } else {
Wimpie 0:9b5b3200688f 161 err = ERROR_CHECKSUM;
mbotkinl 1:42593954052a 162 }
Wimpie 0:9b5b3200688f 163
Wimpie 0:9b5b3200688f 164 return err;
Wimpie 0:9b5b3200688f 165
Wimpie 0:9b5b3200688f 166 }
Wimpie 0:9b5b3200688f 167
Wimpie 0:9b5b3200688f 168 float DHT::CalcTemperature() {
Wimpie 0:9b5b3200688f 169 int v;
Wimpie 0:9b5b3200688f 170
Wimpie 0:9b5b3200688f 171 switch (_DHTtype) {
Wimpie 0:9b5b3200688f 172 case DHT11:
Wimpie 0:9b5b3200688f 173 v = DHT_data[2];
Wimpie 0:9b5b3200688f 174 return float(v);
Wimpie 0:9b5b3200688f 175 case DHT22:
Wimpie 0:9b5b3200688f 176 v = DHT_data[2] & 0x7F;
Wimpie 0:9b5b3200688f 177 v *= 256;
Wimpie 0:9b5b3200688f 178 v += DHT_data[3];
Wimpie 0:9b5b3200688f 179 v /= 10;
Wimpie 0:9b5b3200688f 180 if (DHT_data[2] & 0x80)
Wimpie 0:9b5b3200688f 181 v *= -1;
Wimpie 0:9b5b3200688f 182 return float(v);
Wimpie 0:9b5b3200688f 183 }
Wimpie 0:9b5b3200688f 184 return 0;
Wimpie 0:9b5b3200688f 185 }
Wimpie 0:9b5b3200688f 186
Wimpie 0:9b5b3200688f 187 float DHT::ReadHumidity() {
Wimpie 0:9b5b3200688f 188 return _lastHumidity;
Wimpie 0:9b5b3200688f 189 }
Wimpie 0:9b5b3200688f 190
Wimpie 0:9b5b3200688f 191 float DHT::ConvertCelciustoFarenheit(float celsius) {
Wimpie 0:9b5b3200688f 192 return celsius * 9 / 5 + 32;
Wimpie 0:9b5b3200688f 193 }
Wimpie 0:9b5b3200688f 194
Wimpie 0:9b5b3200688f 195 float DHT::ConvertCelciustoKelvin(float celsius) {
Wimpie 0:9b5b3200688f 196 return celsius + 273.15;
Wimpie 0:9b5b3200688f 197 }
Wimpie 0:9b5b3200688f 198
Wimpie 0:9b5b3200688f 199 // dewPoint function NOAA
Wimpie 0:9b5b3200688f 200 // reference: http://wahiduddin.net/calc/density_algorithms.htm
Wimpie 0:9b5b3200688f 201 float DHT::CalcdewPoint(float celsius, float humidity) {
Wimpie 0:9b5b3200688f 202 float A0= 373.15/(273.15 + celsius);
Wimpie 0:9b5b3200688f 203 float SUM = -7.90298 * (A0-1);
Wimpie 0:9b5b3200688f 204 SUM += 5.02808 * log10(A0);
Wimpie 0:9b5b3200688f 205 SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
Wimpie 0:9b5b3200688f 206 SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
Wimpie 0:9b5b3200688f 207 SUM += log10(1013.246);
Wimpie 0:9b5b3200688f 208 float VP = pow(10, SUM-3) * humidity;
Wimpie 0:9b5b3200688f 209 float T = log(VP/0.61078); // temp var
Wimpie 0:9b5b3200688f 210 return (241.88 * T) / (17.558-T);
Wimpie 0:9b5b3200688f 211 }
Wimpie 0:9b5b3200688f 212
Wimpie 0:9b5b3200688f 213 // delta max = 0.6544 wrt dewPoint()
Wimpie 0:9b5b3200688f 214 // 5x faster than dewPoint()
Wimpie 0:9b5b3200688f 215 // reference: http://en.wikipedia.org/wiki/Dew_point
Wimpie 0:9b5b3200688f 216 float DHT::CalcdewPointFast(float celsius, float humidity)
Wimpie 0:9b5b3200688f 217 {
Wimpie 0:9b5b3200688f 218 float a = 17.271;
Wimpie 0:9b5b3200688f 219 float b = 237.7;
Wimpie 0:9b5b3200688f 220 float temp = (a * celsius) / (b + celsius) + log(humidity/100);
Wimpie 0:9b5b3200688f 221 float Td = (b * temp) / (a - temp);
Wimpie 0:9b5b3200688f 222 return Td;
Wimpie 0:9b5b3200688f 223 }
Wimpie 0:9b5b3200688f 224
Wimpie 0:9b5b3200688f 225 float DHT::ReadTemperature(eScale Scale) {
Wimpie 0:9b5b3200688f 226 if (Scale == FARENHEIT)
Wimpie 0:9b5b3200688f 227 return ConvertCelciustoFarenheit(_lastTemperature);
Wimpie 0:9b5b3200688f 228 else if (Scale == KELVIN)
Wimpie 0:9b5b3200688f 229 return ConvertCelciustoKelvin(_lastTemperature);
Wimpie 0:9b5b3200688f 230 else
Wimpie 0:9b5b3200688f 231 return _lastTemperature;
Wimpie 0:9b5b3200688f 232 }
Wimpie 0:9b5b3200688f 233
Wimpie 0:9b5b3200688f 234 float DHT::CalcHumidity() {
Wimpie 0:9b5b3200688f 235 int v;
Wimpie 0:9b5b3200688f 236
Wimpie 0:9b5b3200688f 237 switch (_DHTtype) {
Wimpie 0:9b5b3200688f 238 case DHT11:
Wimpie 0:9b5b3200688f 239 v = DHT_data[0];
Wimpie 0:9b5b3200688f 240 return float(v);
Wimpie 0:9b5b3200688f 241 case DHT22:
Wimpie 0:9b5b3200688f 242 v = DHT_data[0];
Wimpie 0:9b5b3200688f 243 v *= 256;
Wimpie 0:9b5b3200688f 244 v += DHT_data[1];
Wimpie 0:9b5b3200688f 245 v /= 10;
Wimpie 0:9b5b3200688f 246 return float(v);
Wimpie 0:9b5b3200688f 247 }
Wimpie 0:9b5b3200688f 248 return 0;
Wimpie 0:9b5b3200688f 249 }
Wimpie 0:9b5b3200688f 250
Wimpie 0:9b5b3200688f 251