Giorgos Tsapparellas / DHT11

DHT11 used for Temperature & Humidity sensor.

Dependents:   LoRaWAN_mbed_lmic_agriculture_app

Fork of DHT by Components

DHT.cpp@4:0c34c98a87ec, 2018-04-02 (annotated)

Committer:
GTsapparellas
Date:
Mon Apr 02 12:06:29 2018 +0000
Revision:
4:0c34c98a87ec
Parent:
3:6937e130feca
Child:
5:e7e3db429c9e
DHT11 library employed for temperature & humidity sensor.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
GTsapparellas 4:0c34c98a87ec 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
sam_grove 2:df22ddf10d75 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.
GTsapparellas 4:0c34c98a87ec 31 *
GTsapparellas 4:0c34c98a87ec 32 * /////////////////////////////////////////////////////////////////////////////
GTsapparellas 4:0c34c98a87ec 33 *
GTsapparellas 4:0c34c98a87ec 34 * Used by Giorgos Tsapparellas for Internet of Things (IoT) smart monitoring
GTsapparellas 4:0c34c98a87ec 35 * device for agriculture using LoRaWAN technology.
GTsapparellas 4:0c34c98a87ec 36 *
GTsapparellas 4:0c34c98a87ec 37 * Sensor Used: DHT11 - Digital-output Humidity and Temperature sensor.
GTsapparellas 4:0c34c98a87ec 38 *
GTsapparellas 4:0c34c98a87ec 39 * Date of issued copy: 10 January 2018
GTsapparellas 4:0c34c98a87ec 40 *
GTsapparellas 4:0c34c98a87ec 41 * Modifications:
GTsapparellas 4:0c34c98a87ec 42 * - No external modifications of the existing "AS IT IS" software.
GTsapparellas 4:0c34c98a87ec 43 * - Added some external comments for meeting good principles of
GTsapparellas 4:0c34c98a87ec 44 * source code re-usability.
GTsapparellas 4:0c34c98a87ec 45 ******************************************************************************/
Wimpie 0:9b5b3200688f 46
Wimpie 0:9b5b3200688f 47 #include "DHT.h"
Wimpie 0:9b5b3200688f 48
GTsapparellas 4:0c34c98a87ec 49 #define DHT_DATA_BIT_COUNT 40 // Data bit count set to 40
GTsapparellas 4:0c34c98a87ec 50
GTsapparellas 4:0c34c98a87ec 51 /* Uncomment this line for configuring pc variable for UART usage. */
GTsapparellas 4:0c34c98a87ec 52 //Serial pc(USBTX, USBRX); // UART tranmitter(tx) and receiver(rx).
Wimpie 0:9b5b3200688f 53
GTsapparellas 4:0c34c98a87ec 54 /*
GTsapparellas 4:0c34c98a87ec 55 * DHT constructor.
GTsapparellas 4:0c34c98a87ec 56 * Input parameters: PinName pin
GTsapparellas 4:0c34c98a87ec 57 * eType DHTtype
GTsapparellas 4:0c34c98a87ec 58 *
GTsapparellas 4:0c34c98a87ec 59 */
sam_grove 2:df22ddf10d75 60 DHT::DHT(PinName pin, eType DHTtype)
sam_grove 2:df22ddf10d75 61 {
GTsapparellas 4:0c34c98a87ec 62
Wimpie 0:9b5b3200688f 63 _pin = pin;
Wimpie 0:9b5b3200688f 64 _DHTtype = DHTtype;
sam_grove 2:df22ddf10d75 65 _firsttime = true;
GTsapparellas 4:0c34c98a87ec 66
GTsapparellas 4:0c34c98a87ec 67 } // end of DHT constructor.
sam_grove 2:df22ddf10d75 68
GTsapparellas 4:0c34c98a87ec 69 /*
GTsapparellas 4:0c34c98a87ec 70 * Null DHT destructor.
GTsapparellas 4:0c34c98a87ec 71 *
GTsapparellas 4:0c34c98a87ec 72 */
sam_grove 2:df22ddf10d75 73 DHT::~DHT()
sam_grove 2:df22ddf10d75 74 {
sam_grove 2:df22ddf10d75 75
GTsapparellas 4:0c34c98a87ec 76 } // end of DHT destructor.
Wimpie 0:9b5b3200688f 77
GTsapparellas 4:0c34c98a87ec 78 /*
GTsapparellas 4:0c34c98a87ec 79 * stall DHT function of type eError.
GTsapparellas 4:0c34c98a87ec 80 *
GTsapparellas 4:0c34c98a87ec 81 * Input parameters: DigitalInOut io
GTsapparellas 4:0c34c98a87ec 82 * int const level
GTsapparellas 4:0c34c98a87ec 83 * int const max_time
GTsapparellas 4:0c34c98a87ec 84 *
GTsapparellas 4:0c34c98a87ec 85 * Return: ERROR_NO_PATIENCE or ERROR_NONE
GTsapparellas 4:0c34c98a87ec 86 */
sam_grove 2:df22ddf10d75 87 eError DHT::stall(DigitalInOut &io, int const level, int const max_time)
sam_grove 2:df22ddf10d75 88 {
GTsapparellas 4:0c34c98a87ec 89
sam_grove 2:df22ddf10d75 90 int cnt = 0;
sam_grove 2:df22ddf10d75 91 while (level == io) {
sam_grove 2:df22ddf10d75 92 if (cnt > max_time) {
sam_grove 2:df22ddf10d75 93 return ERROR_NO_PATIENCE;
sam_grove 2:df22ddf10d75 94 }
sam_grove 2:df22ddf10d75 95 cnt++;
sam_grove 2:df22ddf10d75 96 wait_us(1);
sam_grove 2:df22ddf10d75 97 }
sam_grove 2:df22ddf10d75 98 return ERROR_NONE;
GTsapparellas 4:0c34c98a87ec 99
GTsapparellas 4:0c34c98a87ec 100 } // end of stall function.
Wimpie 0:9b5b3200688f 101
GTsapparellas 4:0c34c98a87ec 102 /*
GTsapparellas 4:0c34c98a87ec 103 * readData DHT function of type eError.
GTsapparellas 4:0c34c98a87ec 104 *
GTsapparellas 4:0c34c98a87ec 105 * Input parameters: None
GTsapparellas 4:0c34c98a87ec 106 *
GTsapparellas 4:0c34c98a87ec 107 * Return: Either BUS_BUSY, ERROR_NOT_PRESENT, ERROR_SYNC_TIMEOUT,
GTsapparellas 4:0c34c98a87ec 108 * ERROR_NO_PATIENCE, ERROR_DATA_TIMEOUT or ERROR_CHECKSUM.
GTsapparellas 4:0c34c98a87ec 109 */
sam_grove 2:df22ddf10d75 110 eError DHT::readData()
sam_grove 2:df22ddf10d75 111 {
sam_grove 2:df22ddf10d75 112 uint8_t i = 0, j = 0, b = 0, data_valid = 0;
sam_grove 2:df22ddf10d75 113 uint32_t bit_value[DHT_DATA_BIT_COUNT] = {0};
Wimpie 0:9b5b3200688f 114
Wimpie 0:9b5b3200688f 115 eError err = ERROR_NONE;
Wimpie 0:9b5b3200688f 116 time_t currentTime = time(NULL);
Wimpie 0:9b5b3200688f 117
Wimpie 0:9b5b3200688f 118 DigitalInOut DHT_io(_pin);
Wimpie 0:9b5b3200688f 119
GTsapparellas 4:0c34c98a87ec 120 // I/O must be in high state to start
sam_grove 2:df22ddf10d75 121 if (ERROR_NONE != stall(DHT_io, 0, 250)) {
sam_grove 2:df22ddf10d75 122 return BUS_BUSY;
Wimpie 0:9b5b3200688f 123 }
Wimpie 0:9b5b3200688f 124
GTsapparellas 4:0c34c98a87ec 125 // Start the transfer
Wimpie 0:9b5b3200688f 126 DHT_io.output();
Wimpie 0:9b5b3200688f 127 DHT_io = 0;
sam_grove 3:6937e130feca 128 wait_ms(18);
Wimpie 0:9b5b3200688f 129 DHT_io = 1;
sam_grove 2:df22ddf10d75 130 wait_us(30);
Wimpie 0:9b5b3200688f 131 DHT_io.input();
GTsapparellas 4:0c34c98a87ec 132
GTsapparellas 4:0c34c98a87ec 133 // Wait until the sensor grabs the bus
sam_grove 3:6937e130feca 134 if (ERROR_NONE != stall(DHT_io, 1, 100)) {
sam_grove 2:df22ddf10d75 135 return ERROR_NOT_PRESENT;
Wimpie 0:9b5b3200688f 136 }
GTsapparellas 4:0c34c98a87ec 137 // Sensor should signal low 80us and then high 80us
sam_grove 2:df22ddf10d75 138 if (ERROR_NONE != stall(DHT_io, 0, 100)) {
sam_grove 2:df22ddf10d75 139 return ERROR_SYNC_TIMEOUT;
sam_grove 2:df22ddf10d75 140 }
sam_grove 2:df22ddf10d75 141 if (ERROR_NONE != stall(DHT_io, 1, 100)) {
sam_grove 2:df22ddf10d75 142 return ERROR_NO_PATIENCE;
sam_grove 2:df22ddf10d75 143 }
GTsapparellas 4:0c34c98a87ec 144 // Capture the data
Wimpie 0:9b5b3200688f 145 for (i = 0; i < 5; i++) {
Wimpie 0:9b5b3200688f 146 for (j = 0; j < 8; j++) {
sam_grove 2:df22ddf10d75 147 if (ERROR_NONE != stall(DHT_io, 0, 75)) {
sam_grove 2:df22ddf10d75 148 return ERROR_DATA_TIMEOUT;
sam_grove 2:df22ddf10d75 149 }
GTsapparellas 4:0c34c98a87ec 150 // Logic 0 is 28us max, 1 is 70us
Wimpie 0:9b5b3200688f 151 wait_us(40);
sam_grove 2:df22ddf10d75 152 bit_value[i*8+j] = DHT_io;
sam_grove 2:df22ddf10d75 153 if (ERROR_NONE != stall(DHT_io, 1, 50)) {
sam_grove 2:df22ddf10d75 154 return ERROR_DATA_TIMEOUT;
Wimpie 0:9b5b3200688f 155 }
Wimpie 0:9b5b3200688f 156 }
Wimpie 0:9b5b3200688f 157 }
GTsapparellas 4:0c34c98a87ec 158 // Store the data
Wimpie 0:9b5b3200688f 159 for (i = 0; i < 5; i++) {
Wimpie 0:9b5b3200688f 160 b=0;
Wimpie 0:9b5b3200688f 161 for (j=0; j<8; j++) {
sam_grove 2:df22ddf10d75 162 if (bit_value[i*8+j] == 1) {
sam_grove 2:df22ddf10d75 163 b |= (1 << (7-j));
Wimpie 0:9b5b3200688f 164 }
Wimpie 0:9b5b3200688f 165 }
Wimpie 0:9b5b3200688f 166 DHT_data[i]=b;
Wimpie 0:9b5b3200688f 167 }
Wimpie 0:9b5b3200688f 168
GTsapparellas 4:0c34c98a87ec 169 // Uncomment to see the checksum error if it exists
GTsapparellas 4:0c34c98a87ec 170 //pc.printf(" 0x%02x + 0x%02x + 0x%02x + 0x%02x = 0x%02x \n", DHT_data[0], DHT_data[1], DHT_data[2], DHT_data[3], DHT_data[4]);
sam_grove 2:df22ddf10d75 171 data_valid = DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3];
sam_grove 2:df22ddf10d75 172 if (DHT_data[4] == data_valid) {
Wimpie 0:9b5b3200688f 173 _lastReadTime = currentTime;
sam_grove 2:df22ddf10d75 174 _lastTemperature = CalcTemperature();
sam_grove 2:df22ddf10d75 175 _lastHumidity = CalcHumidity();
Wimpie 0:9b5b3200688f 176
Wimpie 0:9b5b3200688f 177 } else {
Wimpie 0:9b5b3200688f 178 err = ERROR_CHECKSUM;
Wimpie 0:9b5b3200688f 179 }
Wimpie 0:9b5b3200688f 180
Wimpie 0:9b5b3200688f 181 return err;
GTsapparellas 4:0c34c98a87ec 182
GTsapparellas 4:0c34c98a87ec 183 } // end of readData function.
Wimpie 0:9b5b3200688f 184
GTsapparellas 4:0c34c98a87ec 185 /*
GTsapparellas 4:0c34c98a87ec 186 * CalcTemperature DHT function of type float.
GTsapparellas 4:0c34c98a87ec 187 *
GTsapparellas 4:0c34c98a87ec 188 * Input parameters: None
GTsapparellas 4:0c34c98a87ec 189 *
GTsapparellas 4:0c34c98a87ec 190 * Return: float temperature value.
GTsapparellas 4:0c34c98a87ec 191 */
sam_grove 2:df22ddf10d75 192 float DHT::CalcTemperature()
sam_grove 2:df22ddf10d75 193 {
GTsapparellas 4:0c34c98a87ec 194
Wimpie 0:9b5b3200688f 195 int v;
Wimpie 0:9b5b3200688f 196
Wimpie 0:9b5b3200688f 197 switch (_DHTtype) {
Wimpie 0:9b5b3200688f 198 case DHT11:
Wimpie 0:9b5b3200688f 199 v = DHT_data[2];
Wimpie 0:9b5b3200688f 200 return float(v);
Wimpie 0:9b5b3200688f 201 case DHT22:
Wimpie 0:9b5b3200688f 202 v = DHT_data[2] & 0x7F;
Wimpie 0:9b5b3200688f 203 v *= 256;
Wimpie 0:9b5b3200688f 204 v += DHT_data[3];
Wimpie 0:9b5b3200688f 205 v /= 10;
Wimpie 0:9b5b3200688f 206 if (DHT_data[2] & 0x80)
Wimpie 0:9b5b3200688f 207 v *= -1;
Wimpie 0:9b5b3200688f 208 return float(v);
Wimpie 0:9b5b3200688f 209 }
Wimpie 0:9b5b3200688f 210 return 0;
GTsapparellas 4:0c34c98a87ec 211
GTsapparellas 4:0c34c98a87ec 212 } // end of CalcTemperature function.
Wimpie 0:9b5b3200688f 213
GTsapparellas 4:0c34c98a87ec 214 /*
GTsapparellas 4:0c34c98a87ec 215 * ReadHumidity DHT function of type float.
GTsapparellas 4:0c34c98a87ec 216 *
GTsapparellas 4:0c34c98a87ec 217 * Input parameters: None
GTsapparellas 4:0c34c98a87ec 218 *
GTsapparellas 4:0c34c98a87ec 219 * Return: float last humidity value.
GTsapparellas 4:0c34c98a87ec 220 */
sam_grove 2:df22ddf10d75 221 float DHT::ReadHumidity()
sam_grove 2:df22ddf10d75 222 {
Wimpie 0:9b5b3200688f 223 return _lastHumidity;
GTsapparellas 4:0c34c98a87ec 224 } // end of ReadHumidity function.
Wimpie 0:9b5b3200688f 225
GTsapparellas 4:0c34c98a87ec 226 /*
GTsapparellas 4:0c34c98a87ec 227 * ConvertCelsiustoFarenheit DHT function of type float.
GTsapparellas 4:0c34c98a87ec 228 *
GTsapparellas 4:0c34c98a87ec 229 * Input parameters: float const celsius
GTsapparellas 4:0c34c98a87ec 230 *
GTsapparellas 4:0c34c98a87ec 231 * Return: float farenheit temperature value.
GTsapparellas 4:0c34c98a87ec 232 */
sam_grove 2:df22ddf10d75 233 float DHT::ConvertCelciustoFarenheit(float const celsius)
sam_grove 2:df22ddf10d75 234 {
Wimpie 0:9b5b3200688f 235 return celsius * 9 / 5 + 32;
GTsapparellas 4:0c34c98a87ec 236 } // end of ConvertCelciustoFarenheit function.
Wimpie 0:9b5b3200688f 237
GTsapparellas 4:0c34c98a87ec 238 /*
GTsapparellas 4:0c34c98a87ec 239 * ConvertCelsiustoKelvin DHT function of type float.
GTsapparellas 4:0c34c98a87ec 240 *
GTsapparellas 4:0c34c98a87ec 241 * Input parameters: float const celsius
GTsapparellas 4:0c34c98a87ec 242 *
GTsapparellas 4:0c34c98a87ec 243 * Return: float kelvin temperature value.
GTsapparellas 4:0c34c98a87ec 244 */
sam_grove 2:df22ddf10d75 245 float DHT::ConvertCelciustoKelvin(float const celsius)
sam_grove 2:df22ddf10d75 246 {
sam_grove 3:6937e130feca 247 return celsius + 273.15f;
GTsapparellas 4:0c34c98a87ec 248 } // end of ConvertCelciusKelvin function.
Wimpie 0:9b5b3200688f 249
GTsapparellas 4:0c34c98a87ec 250 /*
GTsapparellas 4:0c34c98a87ec 251 * CalcdewPoint DHT function of type float.
GTsapparellas 4:0c34c98a87ec 252 *
GTsapparellas 4:0c34c98a87ec 253 * Input parameters: float const celsius
GTsapparellas 4:0c34c98a87ec 254 * float const humidity
GTsapparellas 4:0c34c98a87ec 255 *
GTsapparellas 4:0c34c98a87ec 256 * Return: dewPoint.
GTsapparellas 4:0c34c98a87ec 257 * Reference: http://wahiduddin.net/calc/density_algorithms.htm
GTsapparellas 4:0c34c98a87ec 258 */
sam_grove 2:df22ddf10d75 259 float DHT::CalcdewPoint(float const celsius, float const humidity)
sam_grove 2:df22ddf10d75 260 {
sam_grove 3:6937e130feca 261 float A0= 373.15f/(273.15f + celsius);
Wimpie 0:9b5b3200688f 262 float SUM = -7.90298 * (A0-1);
sam_grove 3:6937e130feca 263 SUM += 5.02808f * log10(A0);
sam_grove 3:6937e130feca 264 SUM += -1.3816e-7 * (pow(10, (11.344f*(1-1/A0)))-1) ;
Wimpie 0:9b5b3200688f 265 SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
Wimpie 0:9b5b3200688f 266 SUM += log10(1013.246);
Wimpie 0:9b5b3200688f 267 float VP = pow(10, SUM-3) * humidity;
sam_grove 3:6937e130feca 268 float T = log(VP/0.61078f); // temp var
sam_grove 3:6937e130feca 269 return (241.88f * T) / (17.558f-T);
GTsapparellas 4:0c34c98a87ec 270
GTsapparellas 4:0c34c98a87ec 271 } // end of CalcdewPoint function.
Wimpie 0:9b5b3200688f 272
GTsapparellas 4:0c34c98a87ec 273 /*
GTsapparellas 4:0c34c98a87ec 274 * CalcdewPointFast DHT function of type float.
GTsapparellas 4:0c34c98a87ec 275 *
GTsapparellas 4:0c34c98a87ec 276 * Input parameters: float const celsius
GTsapparellas 4:0c34c98a87ec 277 * float const humidity
GTsapparellas 4:0c34c98a87ec 278 *
GTsapparellas 4:0c34c98a87ec 279 * Return: 5x faster dewPoint.
GTsapparellas 4:0c34c98a87ec 280 * Reference: http://en.wikipedia.org/wiki/Dew_point
GTsapparellas 4:0c34c98a87ec 281 */
sam_grove 2:df22ddf10d75 282 float DHT::CalcdewPointFast(float const celsius, float const humidity)
Wimpie 0:9b5b3200688f 283 {
sam_grove 2:df22ddf10d75 284 float a = 17.271;
sam_grove 2:df22ddf10d75 285 float b = 237.7;
sam_grove 2:df22ddf10d75 286 float temp = (a * celsius) / (b + celsius) + log(humidity/100);
sam_grove 2:df22ddf10d75 287 float Td = (b * temp) / (a - temp);
sam_grove 2:df22ddf10d75 288 return Td;
GTsapparellas 4:0c34c98a87ec 289
GTsapparellas 4:0c34c98a87ec 290 } // end of CalcdewPointFast function
Wimpie 0:9b5b3200688f 291
GTsapparellas 4:0c34c98a87ec 292 /*
GTsapparellas 4:0c34c98a87ec 293 * ReadTemperature DHT function of type float.
GTsapparellas 4:0c34c98a87ec 294 *
GTsapparellas 4:0c34c98a87ec 295 * Input parameters: eScale Scale
GTsapparellas 4:0c34c98a87ec 296 *
GTsapparellas 4:0c34c98a87ec 297 * Return: float scaled temperature value.
GTsapparellas 4:0c34c98a87ec 298 * Reference: http://en.wikipedia.org/wiki/Dew_point
GTsapparellas 4:0c34c98a87ec 299 */
sam_grove 2:df22ddf10d75 300 float DHT::ReadTemperature(eScale Scale)
sam_grove 2:df22ddf10d75 301 {
Wimpie 0:9b5b3200688f 302 if (Scale == FARENHEIT)
Wimpie 0:9b5b3200688f 303 return ConvertCelciustoFarenheit(_lastTemperature);
Wimpie 0:9b5b3200688f 304 else if (Scale == KELVIN)
Wimpie 0:9b5b3200688f 305 return ConvertCelciustoKelvin(_lastTemperature);
Wimpie 0:9b5b3200688f 306 else
Wimpie 0:9b5b3200688f 307 return _lastTemperature;
GTsapparellas 4:0c34c98a87ec 308 } // end of ReadTemperature function.
Wimpie 0:9b5b3200688f 309
GTsapparellas 4:0c34c98a87ec 310 /*
GTsapparellas 4:0c34c98a87ec 311 * Calc DHT function of type float.
GTsapparellas 4:0c34c98a87ec 312 *
GTsapparellas 4:0c34c98a87ec 313 * Input parameters: None
GTsapparellas 4:0c34c98a87ec 314 *
GTsapparellas 4:0c34c98a87ec 315 * Return: float humidity value.
GTsapparellas 4:0c34c98a87ec 316 */
sam_grove 2:df22ddf10d75 317 float DHT::CalcHumidity()
sam_grove 2:df22ddf10d75 318 {
Wimpie 0:9b5b3200688f 319 int v;
Wimpie 0:9b5b3200688f 320
Wimpie 0:9b5b3200688f 321 switch (_DHTtype) {
Wimpie 0:9b5b3200688f 322 case DHT11:
Wimpie 0:9b5b3200688f 323 v = DHT_data[0];
Wimpie 0:9b5b3200688f 324 return float(v);
Wimpie 0:9b5b3200688f 325 case DHT22:
Wimpie 0:9b5b3200688f 326 v = DHT_data[0];
Wimpie 0:9b5b3200688f 327 v *= 256;
Wimpie 0:9b5b3200688f 328 v += DHT_data[1];
Wimpie 0:9b5b3200688f 329 v /= 10;
Wimpie 0:9b5b3200688f 330 return float(v);
Wimpie 0:9b5b3200688f 331 }
Wimpie 0:9b5b3200688f 332 return 0;
GTsapparellas 4:0c34c98a87ec 333 } // end of CalcHumidity function.