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DHT/DHT.cpp@0:1501dea8d383, 2015-10-05 (annotated)

Committer:
schenk
Date:
Mon Oct 05 06:42:59 2015 +0000
Revision:
0:1501dea8d383
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schenk 0:1501dea8d383 1 /*
schenk 0:1501dea8d383 2 * DHT Library for Digital-output Humidity and Temperature sensors
schenk 0:1501dea8d383 3 *
schenk 0:1501dea8d383 4 * Works with DHT11, DHT22
schenk 0:1501dea8d383 5 * SEN11301P, Grove - Temperature&Humidity Sensor (Seeed Studio)
schenk 0:1501dea8d383 6 * SEN51035P, Grove - Temperature&Humidity Sensor Pro (Seeed Studio)
schenk 0:1501dea8d383 7 * AM2302 , temperature-humidity sensor
schenk 0:1501dea8d383 8 * HM2303 , Digital-output humidity and temperature sensor
schenk 0:1501dea8d383 9 *
schenk 0:1501dea8d383 10 * Copyright (C) Wim De Roeve
schenk 0:1501dea8d383 11 * based on DHT22 sensor library by HO WING KIT
schenk 0:1501dea8d383 12 * Arduino DHT11 library
schenk 0:1501dea8d383 13 *
schenk 0:1501dea8d383 14 * Permission is hereby granted, free of charge, to any person obtaining a copy
schenk 0:1501dea8d383 15 * of this software and associated documnetation files (the "Software"), to deal
schenk 0:1501dea8d383 16 * in the Software without restriction, including without limitation the rights
schenk 0:1501dea8d383 17 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
schenk 0:1501dea8d383 18 * copies of the Software, and to permit persons to whom the Software is
schenk 0:1501dea8d383 19 * furished to do so, subject to the following conditions:
schenk 0:1501dea8d383 20 *
schenk 0:1501dea8d383 21 * The above copyright notice and this permission notice shall be included in
schenk 0:1501dea8d383 22 * all copies or substantial portions of the Software.
schenk 0:1501dea8d383 23 *
schenk 0:1501dea8d383 24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
schenk 0:1501dea8d383 25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
schenk 0:1501dea8d383 26 * FITNESS OR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
schenk 0:1501dea8d383 27 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
schenk 0:1501dea8d383 28 * LIABILITY WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
schenk 0:1501dea8d383 29 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
schenk 0:1501dea8d383 30 * THE SOFTWARE.
schenk 0:1501dea8d383 31 */
schenk 0:1501dea8d383 32
schenk 0:1501dea8d383 33 #include "DHT.h"
schenk 0:1501dea8d383 34
schenk 0:1501dea8d383 35 #define DHT_DATA_BIT_COUNT 40
schenk 0:1501dea8d383 36
schenk 0:1501dea8d383 37 DHT::DHT(PinName pin, eType DHTtype)
schenk 0:1501dea8d383 38 {
schenk 0:1501dea8d383 39 _pin = pin;
schenk 0:1501dea8d383 40 _DHTtype = DHTtype;
schenk 0:1501dea8d383 41 _firsttime = true;
schenk 0:1501dea8d383 42 }
schenk 0:1501dea8d383 43
schenk 0:1501dea8d383 44 DHT::~DHT()
schenk 0:1501dea8d383 45 {
schenk 0:1501dea8d383 46
schenk 0:1501dea8d383 47 }
schenk 0:1501dea8d383 48
schenk 0:1501dea8d383 49 eError DHT::stall(DigitalInOut &io, int const level, int const max_time)
schenk 0:1501dea8d383 50 {
schenk 0:1501dea8d383 51 int cnt = 0;
schenk 0:1501dea8d383 52 while (level == io) {
schenk 0:1501dea8d383 53 if (cnt > max_time) {
schenk 0:1501dea8d383 54 return ERROR_NO_PATIENCE;
schenk 0:1501dea8d383 55 }
schenk 0:1501dea8d383 56 cnt++;
schenk 0:1501dea8d383 57 wait_us(1);
schenk 0:1501dea8d383 58 }
schenk 0:1501dea8d383 59 return ERROR_NONE;
schenk 0:1501dea8d383 60 }
schenk 0:1501dea8d383 61
schenk 0:1501dea8d383 62 eError DHT::readData()
schenk 0:1501dea8d383 63 {
schenk 0:1501dea8d383 64 uint8_t i = 0, j = 0, b = 0, data_valid = 0;
schenk 0:1501dea8d383 65 uint32_t bit_value[DHT_DATA_BIT_COUNT] = {0};
schenk 0:1501dea8d383 66
schenk 0:1501dea8d383 67 eError err = ERROR_NONE;
schenk 0:1501dea8d383 68 time_t currentTime = time(NULL);
schenk 0:1501dea8d383 69
schenk 0:1501dea8d383 70 DigitalInOut DHT_io(_pin);
schenk 0:1501dea8d383 71
schenk 0:1501dea8d383 72 // IO must be in hi state to start
schenk 0:1501dea8d383 73 if (ERROR_NONE != stall(DHT_io, 0, 250)) {
schenk 0:1501dea8d383 74 return BUS_BUSY;
schenk 0:1501dea8d383 75 }
schenk 0:1501dea8d383 76
schenk 0:1501dea8d383 77 // start the transfer
schenk 0:1501dea8d383 78 DHT_io.output();
schenk 0:1501dea8d383 79 DHT_io = 0;
schenk 0:1501dea8d383 80 // only 500uS for DHT22 but 18ms for DHT11
schenk 0:1501dea8d383 81 (_DHTtype == 11) ? wait_ms(18) : wait(1);
schenk 0:1501dea8d383 82 DHT_io = 1;
schenk 0:1501dea8d383 83 wait_us(30);
schenk 0:1501dea8d383 84 DHT_io.input();
schenk 0:1501dea8d383 85 // wait till the sensor grabs the bus
schenk 0:1501dea8d383 86 if (ERROR_NONE != stall(DHT_io, 1, 40)) {
schenk 0:1501dea8d383 87 return ERROR_NOT_PRESENT;
schenk 0:1501dea8d383 88 }
schenk 0:1501dea8d383 89 // sensor should signal low 80us and then hi 80us
schenk 0:1501dea8d383 90 if (ERROR_NONE != stall(DHT_io, 0, 100)) {
schenk 0:1501dea8d383 91 return ERROR_SYNC_TIMEOUT;
schenk 0:1501dea8d383 92 }
schenk 0:1501dea8d383 93 if (ERROR_NONE != stall(DHT_io, 1, 100)) {
schenk 0:1501dea8d383 94 return ERROR_NO_PATIENCE;
schenk 0:1501dea8d383 95 }
schenk 0:1501dea8d383 96 // capture the data
schenk 0:1501dea8d383 97 for (i = 0; i < 5; i++) {
schenk 0:1501dea8d383 98 for (j = 0; j < 8; j++) {
schenk 0:1501dea8d383 99 if (ERROR_NONE != stall(DHT_io, 0, 75)) {
schenk 0:1501dea8d383 100 return ERROR_DATA_TIMEOUT;
schenk 0:1501dea8d383 101 }
schenk 0:1501dea8d383 102 // logic 0 is 28us max, 1 is 70us
schenk 0:1501dea8d383 103 wait_us(40);
schenk 0:1501dea8d383 104 bit_value[i*8+j] = DHT_io;
schenk 0:1501dea8d383 105 if (ERROR_NONE != stall(DHT_io, 1, 50)) {
schenk 0:1501dea8d383 106 return ERROR_DATA_TIMEOUT;
schenk 0:1501dea8d383 107 }
schenk 0:1501dea8d383 108 }
schenk 0:1501dea8d383 109 }
schenk 0:1501dea8d383 110 // store the data
schenk 0:1501dea8d383 111 for (i = 0; i < 5; i++) {
schenk 0:1501dea8d383 112 b=0;
schenk 0:1501dea8d383 113 for (j=0; j<8; j++) {
schenk 0:1501dea8d383 114 if (bit_value[i*8+j] == 1) {
schenk 0:1501dea8d383 115 b |= (1 << (7-j));
schenk 0:1501dea8d383 116 }
schenk 0:1501dea8d383 117 }
schenk 0:1501dea8d383 118 DHT_data[i]=b;
schenk 0:1501dea8d383 119 }
schenk 0:1501dea8d383 120
schenk 0:1501dea8d383 121 // uncomment to see the checksum error if it exists
schenk 0:1501dea8d383 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]);
schenk 0:1501dea8d383 123 data_valid = DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3];
schenk 0:1501dea8d383 124 if (DHT_data[4] == data_valid) {
schenk 0:1501dea8d383 125 _lastReadTime = currentTime;
schenk 0:1501dea8d383 126 _lastTemperature = CalcTemperature();
schenk 0:1501dea8d383 127 _lastHumidity = CalcHumidity();
schenk 0:1501dea8d383 128
schenk 0:1501dea8d383 129 } else {
schenk 0:1501dea8d383 130 err = ERROR_CHECKSUM;
schenk 0:1501dea8d383 131 }
schenk 0:1501dea8d383 132
schenk 0:1501dea8d383 133 return err;
schenk 0:1501dea8d383 134
schenk 0:1501dea8d383 135 }
schenk 0:1501dea8d383 136
schenk 0:1501dea8d383 137 float DHT::CalcTemperature()
schenk 0:1501dea8d383 138 {
schenk 0:1501dea8d383 139 int v;
schenk 0:1501dea8d383 140
schenk 0:1501dea8d383 141 switch (_DHTtype) {
schenk 0:1501dea8d383 142 case DHT11:
schenk 0:1501dea8d383 143 v = DHT_data[2];
schenk 0:1501dea8d383 144 return float(v);
schenk 0:1501dea8d383 145 case DHT22:
schenk 0:1501dea8d383 146 v = DHT_data[2] & 0x7F;
schenk 0:1501dea8d383 147 v *= 256;
schenk 0:1501dea8d383 148 v += DHT_data[3];
schenk 0:1501dea8d383 149 v /= 10;
schenk 0:1501dea8d383 150 if (DHT_data[2] & 0x80)
schenk 0:1501dea8d383 151 v *= -1;
schenk 0:1501dea8d383 152 return float(v);
schenk 0:1501dea8d383 153 }
schenk 0:1501dea8d383 154 return 0;
schenk 0:1501dea8d383 155 }
schenk 0:1501dea8d383 156
schenk 0:1501dea8d383 157 float DHT::ReadHumidity()
schenk 0:1501dea8d383 158 {
schenk 0:1501dea8d383 159 return _lastHumidity;
schenk 0:1501dea8d383 160 }
schenk 0:1501dea8d383 161
schenk 0:1501dea8d383 162 float DHT::ConvertCelciustoFarenheit(float const celsius)
schenk 0:1501dea8d383 163 {
schenk 0:1501dea8d383 164 return celsius * 9 / 5 + 32;
schenk 0:1501dea8d383 165 }
schenk 0:1501dea8d383 166
schenk 0:1501dea8d383 167 float DHT::ConvertCelciustoKelvin(float const celsius)
schenk 0:1501dea8d383 168 {
schenk 0:1501dea8d383 169 return celsius + 273.15;
schenk 0:1501dea8d383 170 }
schenk 0:1501dea8d383 171
schenk 0:1501dea8d383 172 // dewPoint function NOAA
schenk 0:1501dea8d383 173 // reference: http://wahiduddin.net/calc/density_algorithms.htm
schenk 0:1501dea8d383 174 float DHT::CalcdewPoint(float const celsius, float const humidity)
schenk 0:1501dea8d383 175 {
schenk 0:1501dea8d383 176 float A0= 373.15/(273.15 + celsius);
schenk 0:1501dea8d383 177 float SUM = -7.90298 * (A0-1);
schenk 0:1501dea8d383 178 SUM += 5.02808 * log10(A0);
schenk 0:1501dea8d383 179 SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
schenk 0:1501dea8d383 180 SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
schenk 0:1501dea8d383 181 SUM += log10(1013.246);
schenk 0:1501dea8d383 182 float VP = pow(10, SUM-3) * humidity;
schenk 0:1501dea8d383 183 float T = log(VP/0.61078); // temp var
schenk 0:1501dea8d383 184 return (241.88 * T) / (17.558-T);
schenk 0:1501dea8d383 185 }
schenk 0:1501dea8d383 186
schenk 0:1501dea8d383 187 // delta max = 0.6544 wrt dewPoint()
schenk 0:1501dea8d383 188 // 5x faster than dewPoint()
schenk 0:1501dea8d383 189 // reference: http://en.wikipedia.org/wiki/Dew_point
schenk 0:1501dea8d383 190 float DHT::CalcdewPointFast(float const celsius, float const humidity)
schenk 0:1501dea8d383 191 {
schenk 0:1501dea8d383 192 float a = 17.271;
schenk 0:1501dea8d383 193 float b = 237.7;
schenk 0:1501dea8d383 194 float temp = (a * celsius) / (b + celsius) + log(humidity/100);
schenk 0:1501dea8d383 195 float Td = (b * temp) / (a - temp);
schenk 0:1501dea8d383 196 return Td;
schenk 0:1501dea8d383 197 }
schenk 0:1501dea8d383 198
schenk 0:1501dea8d383 199 float DHT::ReadTemperature(eScale Scale)
schenk 0:1501dea8d383 200 {
schenk 0:1501dea8d383 201 if (Scale == FARENHEIT)
schenk 0:1501dea8d383 202 return ConvertCelciustoFarenheit(_lastTemperature);
schenk 0:1501dea8d383 203 else if (Scale == KELVIN)
schenk 0:1501dea8d383 204 return ConvertCelciustoKelvin(_lastTemperature);
schenk 0:1501dea8d383 205 else
schenk 0:1501dea8d383 206 return _lastTemperature;
schenk 0:1501dea8d383 207 }
schenk 0:1501dea8d383 208
schenk 0:1501dea8d383 209 float DHT::CalcHumidity()
schenk 0:1501dea8d383 210 {
schenk 0:1501dea8d383 211 int v;
schenk 0:1501dea8d383 212
schenk 0:1501dea8d383 213 switch (_DHTtype) {
schenk 0:1501dea8d383 214 case DHT11:
schenk 0:1501dea8d383 215 v = DHT_data[0];
schenk 0:1501dea8d383 216 return float(v);
schenk 0:1501dea8d383 217 case DHT22:
schenk 0:1501dea8d383 218 v = DHT_data[0];
schenk 0:1501dea8d383 219 v *= 256;
schenk 0:1501dea8d383 220 v += DHT_data[1];
schenk 0:1501dea8d383 221 v /= 10;
schenk 0:1501dea8d383 222 return float(v);
schenk 0:1501dea8d383 223 }
schenk 0:1501dea8d383 224 return 0;
schenk 0:1501dea8d383 225 }
schenk 0:1501dea8d383 226
schenk 0:1501dea8d383 227