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source/DHT.cpp@1:72dca6351fc1, 2018-01-02 (annotated)

Committer:
trnoo
Date:
Tue Jan 02 14:27:09 2018 +0000
Revision:
1:72dca6351fc1
21300206 KimChoongMan

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trnoo 1:72dca6351fc1 1 /*
trnoo 1:72dca6351fc1 2 * DHT Library for Digital-output Humidity and Temperature sensors
trnoo 1:72dca6351fc1 3 *
trnoo 1:72dca6351fc1 4 * Works with DHT11, DHT22
trnoo 1:72dca6351fc1 5 * SEN11301P, Grove - Temperature&Humidity Sensor (Seeed Studio)
trnoo 1:72dca6351fc1 6 * SEN51035P, Grove - Temperature&Humidity Sensor Pro (Seeed Studio)
trnoo 1:72dca6351fc1 7 * AM2302 , temperature-humidity sensor
trnoo 1:72dca6351fc1 8 * HM2303 , Digital-output humidity and temperature sensor
trnoo 1:72dca6351fc1 9 *
trnoo 1:72dca6351fc1 10 * Copyright (C) Wim De Roeve
trnoo 1:72dca6351fc1 11 * based on DHT22 sensor library by HO WING KIT
trnoo 1:72dca6351fc1 12 * Arduino DHT11 library
trnoo 1:72dca6351fc1 13 *
trnoo 1:72dca6351fc1 14 * Permission is hereby granted, free of charge, to any person obtaining a copy
trnoo 1:72dca6351fc1 15 * of this software and associated documnetation files (the "Software"), to deal
trnoo 1:72dca6351fc1 16 * in the Software without restriction, including without limitation the rights
trnoo 1:72dca6351fc1 17 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
trnoo 1:72dca6351fc1 18 * copies of the Software, and to permit persons to whom the Software is
trnoo 1:72dca6351fc1 19 * furished to do so, subject to the following conditions:
trnoo 1:72dca6351fc1 20 *
trnoo 1:72dca6351fc1 21 * The above copyright notice and this permission notice shall be included in
trnoo 1:72dca6351fc1 22 * all copies or substantial portions of the Software.
trnoo 1:72dca6351fc1 23 *
trnoo 1:72dca6351fc1 24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
trnoo 1:72dca6351fc1 25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
trnoo 1:72dca6351fc1 26 * FITNESS OR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
trnoo 1:72dca6351fc1 27 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
trnoo 1:72dca6351fc1 28 * LIABILITY WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
trnoo 1:72dca6351fc1 29 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
trnoo 1:72dca6351fc1 30 * THE SOFTWARE.
trnoo 1:72dca6351fc1 31 */
trnoo 1:72dca6351fc1 32
trnoo 1:72dca6351fc1 33 #include "DHT.h"
trnoo 1:72dca6351fc1 34
trnoo 1:72dca6351fc1 35 #define DHT_DATA_BIT_COUNT 40
trnoo 1:72dca6351fc1 36
trnoo 1:72dca6351fc1 37 DHT::DHT(PinName pin, eType DHTtype)
trnoo 1:72dca6351fc1 38 {
trnoo 1:72dca6351fc1 39 _pin = pin;
trnoo 1:72dca6351fc1 40 _DHTtype = DHTtype;
trnoo 1:72dca6351fc1 41 _firsttime = true;
trnoo 1:72dca6351fc1 42 }
trnoo 1:72dca6351fc1 43
trnoo 1:72dca6351fc1 44 DHT::~DHT()
trnoo 1:72dca6351fc1 45 {
trnoo 1:72dca6351fc1 46
trnoo 1:72dca6351fc1 47 }
trnoo 1:72dca6351fc1 48
trnoo 1:72dca6351fc1 49 eError DHT::stall(DigitalInOut &io, int const level, int const max_time)
trnoo 1:72dca6351fc1 50 {
trnoo 1:72dca6351fc1 51 int cnt = 0;
trnoo 1:72dca6351fc1 52 while (level == io) {
trnoo 1:72dca6351fc1 53 if (cnt > max_time) {
trnoo 1:72dca6351fc1 54 return ERROR_NO_PATIENCE;
trnoo 1:72dca6351fc1 55 }
trnoo 1:72dca6351fc1 56 cnt++;
trnoo 1:72dca6351fc1 57 wait_us(1);
trnoo 1:72dca6351fc1 58 }
trnoo 1:72dca6351fc1 59 return ERROR_NONE;
trnoo 1:72dca6351fc1 60 }
trnoo 1:72dca6351fc1 61
trnoo 1:72dca6351fc1 62 eError DHT::readData()
trnoo 1:72dca6351fc1 63 {
trnoo 1:72dca6351fc1 64 uint8_t i = 0, j = 0, b = 0, data_valid = 0;
trnoo 1:72dca6351fc1 65 uint32_t bit_value[DHT_DATA_BIT_COUNT] = {0};
trnoo 1:72dca6351fc1 66
trnoo 1:72dca6351fc1 67 eError err = ERROR_NONE;
trnoo 1:72dca6351fc1 68 time_t currentTime = time(NULL);
trnoo 1:72dca6351fc1 69
trnoo 1:72dca6351fc1 70 DigitalInOut DHT_io(_pin);
trnoo 1:72dca6351fc1 71
trnoo 1:72dca6351fc1 72 // IO must be in hi state to start
trnoo 1:72dca6351fc1 73 if (ERROR_NONE != stall(DHT_io, 0, 250)) {
trnoo 1:72dca6351fc1 74 return BUS_BUSY;
trnoo 1:72dca6351fc1 75 }
trnoo 1:72dca6351fc1 76
trnoo 1:72dca6351fc1 77 // start the transfer
trnoo 1:72dca6351fc1 78 DHT_io.output();
trnoo 1:72dca6351fc1 79 DHT_io = 0;
trnoo 1:72dca6351fc1 80 // only 500uS for DHT22 but 18ms for DHT11
trnoo 1:72dca6351fc1 81 (_DHTtype == 11) ? wait_ms(18) : wait(0.0005);
trnoo 1:72dca6351fc1 82 DHT_io = 1;
trnoo 1:72dca6351fc1 83 wait_us(30);
trnoo 1:72dca6351fc1 84 DHT_io.input();
trnoo 1:72dca6351fc1 85 // wait till the sensor grabs the bus
trnoo 1:72dca6351fc1 86 if (ERROR_NONE != stall(DHT_io, 1, 40)) {
trnoo 1:72dca6351fc1 87 return ERROR_NOT_PRESENT;
trnoo 1:72dca6351fc1 88 }
trnoo 1:72dca6351fc1 89 // sensor should signal low 80us and then hi 80us
trnoo 1:72dca6351fc1 90 if (ERROR_NONE != stall(DHT_io, 0, 100)) {
trnoo 1:72dca6351fc1 91 return ERROR_SYNC_TIMEOUT;
trnoo 1:72dca6351fc1 92 }
trnoo 1:72dca6351fc1 93 if (ERROR_NONE != stall(DHT_io, 1, 100)) {
trnoo 1:72dca6351fc1 94 return ERROR_NO_PATIENCE;
trnoo 1:72dca6351fc1 95 }
trnoo 1:72dca6351fc1 96 // capture the data
trnoo 1:72dca6351fc1 97 for (i = 0; i < 5; i++) {
trnoo 1:72dca6351fc1 98 for (j = 0; j < 8; j++) {
trnoo 1:72dca6351fc1 99 if (ERROR_NONE != stall(DHT_io, 0, 75)) {
trnoo 1:72dca6351fc1 100 return ERROR_DATA_TIMEOUT;
trnoo 1:72dca6351fc1 101 }
trnoo 1:72dca6351fc1 102 // logic 0 is 28us max, 1 is 70us
trnoo 1:72dca6351fc1 103 wait_us(40);
trnoo 1:72dca6351fc1 104 bit_value[i*8+j] = DHT_io;
trnoo 1:72dca6351fc1 105 if (ERROR_NONE != stall(DHT_io, 1, 50)) {
trnoo 1:72dca6351fc1 106 return ERROR_DATA_TIMEOUT;
trnoo 1:72dca6351fc1 107 }
trnoo 1:72dca6351fc1 108 }
trnoo 1:72dca6351fc1 109 }
trnoo 1:72dca6351fc1 110 // store the data
trnoo 1:72dca6351fc1 111 for (i = 0; i < 5; i++) {
trnoo 1:72dca6351fc1 112 b=0;
trnoo 1:72dca6351fc1 113 for (j=0; j<8; j++) {
trnoo 1:72dca6351fc1 114 if (bit_value[i*8+j] == 1) {
trnoo 1:72dca6351fc1 115 b |= (1 << (7-j));
trnoo 1:72dca6351fc1 116 }
trnoo 1:72dca6351fc1 117 }
trnoo 1:72dca6351fc1 118 DHT_data[i]=b;
trnoo 1:72dca6351fc1 119 }
trnoo 1:72dca6351fc1 120
trnoo 1:72dca6351fc1 121 // uncomment to see the checksum error if it exists
trnoo 1:72dca6351fc1 122 //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]);
trnoo 1:72dca6351fc1 123 data_valid = DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3];
trnoo 1:72dca6351fc1 124 if (DHT_data[4] == data_valid) {
trnoo 1:72dca6351fc1 125 _lastReadTime = currentTime;
trnoo 1:72dca6351fc1 126 _lastTemperature = CalcTemperature();
trnoo 1:72dca6351fc1 127 _lastHumidity = CalcHumidity();
trnoo 1:72dca6351fc1 128
trnoo 1:72dca6351fc1 129 } else {
trnoo 1:72dca6351fc1 130 err = ERROR_CHECKSUM;
trnoo 1:72dca6351fc1 131 }
trnoo 1:72dca6351fc1 132
trnoo 1:72dca6351fc1 133 return err;
trnoo 1:72dca6351fc1 134
trnoo 1:72dca6351fc1 135 }
trnoo 1:72dca6351fc1 136
trnoo 1:72dca6351fc1 137 float DHT::CalcTemperature()
trnoo 1:72dca6351fc1 138 {
trnoo 1:72dca6351fc1 139 float v;
trnoo 1:72dca6351fc1 140
trnoo 1:72dca6351fc1 141 switch (_DHTtype) {
trnoo 1:72dca6351fc1 142 case DHT11:
trnoo 1:72dca6351fc1 143 v = DHT_data[2];
trnoo 1:72dca6351fc1 144 return float(v);
trnoo 1:72dca6351fc1 145 case DHT22:
trnoo 1:72dca6351fc1 146 v = DHT_data[2] & 0x7F;
trnoo 1:72dca6351fc1 147 v *= 256;
trnoo 1:72dca6351fc1 148 v += DHT_data[3];
trnoo 1:72dca6351fc1 149 v /= 10;
trnoo 1:72dca6351fc1 150 if (DHT_data[2] & 0x80)
trnoo 1:72dca6351fc1 151 v *= -1;
trnoo 1:72dca6351fc1 152 return float(v);
trnoo 1:72dca6351fc1 153 }
trnoo 1:72dca6351fc1 154 return 0;
trnoo 1:72dca6351fc1 155 }
trnoo 1:72dca6351fc1 156
trnoo 1:72dca6351fc1 157 float DHT::ReadHumidity()
trnoo 1:72dca6351fc1 158 {
trnoo 1:72dca6351fc1 159 return _lastHumidity+30;
trnoo 1:72dca6351fc1 160 }
trnoo 1:72dca6351fc1 161
trnoo 1:72dca6351fc1 162 float DHT::ConvertCelciustoFarenheit(float const celsius)
trnoo 1:72dca6351fc1 163 {
trnoo 1:72dca6351fc1 164 return celsius * 9 / 5 + 32;
trnoo 1:72dca6351fc1 165 }
trnoo 1:72dca6351fc1 166
trnoo 1:72dca6351fc1 167 float DHT::ConvertCelciustoKelvin(float const celsius)
trnoo 1:72dca6351fc1 168 {
trnoo 1:72dca6351fc1 169 return celsius + 273.15;
trnoo 1:72dca6351fc1 170 }
trnoo 1:72dca6351fc1 171
trnoo 1:72dca6351fc1 172 // dewPoint function NOAA
trnoo 1:72dca6351fc1 173 // reference: http://wahiduddin.net/calc/density_algorithms.htm
trnoo 1:72dca6351fc1 174 float DHT::CalcdewPoint(float const celsius, float const humidity)
trnoo 1:72dca6351fc1 175 {
trnoo 1:72dca6351fc1 176 float A0= 373.15/(273.15 + celsius);
trnoo 1:72dca6351fc1 177 float SUM = -7.90298 * (A0-1);
trnoo 1:72dca6351fc1 178 SUM += 5.02808 * log10(A0);
trnoo 1:72dca6351fc1 179 SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
trnoo 1:72dca6351fc1 180 SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
trnoo 1:72dca6351fc1 181 SUM += log10(1013.246);
trnoo 1:72dca6351fc1 182 float VP = pow(10, SUM-3) * (humidity);
trnoo 1:72dca6351fc1 183 float T = log(VP/0.61078); // temp var
trnoo 1:72dca6351fc1 184 return (241.88 * T) / (17.558-T);
trnoo 1:72dca6351fc1 185 }
trnoo 1:72dca6351fc1 186
trnoo 1:72dca6351fc1 187 // delta max = 0.6544 wrt dewPoint()
trnoo 1:72dca6351fc1 188 // 5x faster than dewPoint()
trnoo 1:72dca6351fc1 189 // reference: http://en.wikipedia.org/wiki/Dew_point
trnoo 1:72dca6351fc1 190 /*float DHT::CalcdewPointFast(float const celsius, float const humidity)
trnoo 1:72dca6351fc1 191 {
trnoo 1:72dca6351fc1 192 float a = 17.271;
trnoo 1:72dca6351fc1 193 float b = 237.7;
trnoo 1:72dca6351fc1 194 float temp = (a * celsius) / (b + celsius) + log(humidity/100);
trnoo 1:72dca6351fc1 195 float Td = (b * temp) / (a - temp);
trnoo 1:72dca6351fc1 196 return Td;
trnoo 1:72dca6351fc1 197 }*/
trnoo 1:72dca6351fc1 198
trnoo 1:72dca6351fc1 199 float DHT::ReadTemperature(eScale Scale)
trnoo 1:72dca6351fc1 200 {
trnoo 1:72dca6351fc1 201 if (Scale == FARENHEIT)
trnoo 1:72dca6351fc1 202 return ConvertCelciustoFarenheit(_lastTemperature);
trnoo 1:72dca6351fc1 203 else if (Scale == KELVIN)
trnoo 1:72dca6351fc1 204 return ConvertCelciustoKelvin(_lastTemperature);
trnoo 1:72dca6351fc1 205 else
trnoo 1:72dca6351fc1 206 return _lastTemperature;
trnoo 1:72dca6351fc1 207 }
trnoo 1:72dca6351fc1 208
trnoo 1:72dca6351fc1 209 float DHT::CalcHumidity()
trnoo 1:72dca6351fc1 210 {
trnoo 1:72dca6351fc1 211 float v;
trnoo 1:72dca6351fc1 212
trnoo 1:72dca6351fc1 213 switch (_DHTtype) {
trnoo 1:72dca6351fc1 214 case DHT11:
trnoo 1:72dca6351fc1 215 v = DHT_data[0];
trnoo 1:72dca6351fc1 216 return float(v);
trnoo 1:72dca6351fc1 217 case DHT22:
trnoo 1:72dca6351fc1 218 v = DHT_data[0];
trnoo 1:72dca6351fc1 219 v *= 256;
trnoo 1:72dca6351fc1 220 v += DHT_data[1];
trnoo 1:72dca6351fc1 221 v /= 10;
trnoo 1:72dca6351fc1 222 return float(v);
trnoo 1:72dca6351fc1 223 }
trnoo 1:72dca6351fc1 224 return 0;
trnoo 1:72dca6351fc1 225 }
trnoo 1:72dca6351fc1 226