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/*
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* DHT Library for Digital-output Humidity and Temperature sensors
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*
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* Works with DHT11, DHT22
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* SEN11301P, Grove - Temperature&Humidity Sensor (Seeed Studio)
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* SEN51035P, Grove - Temperature&Humidity Sensor Pro (Seeed Studio)
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* AM2302 , temperature-humidity sensor
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* HM2303 , Digital-output humidity and temperature sensor
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*
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* Copyright (C) Wim De Roeve
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* based on DHT22 sensor library by HO WING KIT
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* Arduino DHT11 library
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documnetation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS OR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "DHT.h"
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#define DHT_DATA_BIT_COUNT 41
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DHT::DHT(PinName pin,int DHTtype) {
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_pin = pin;
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_DHTtype = DHTtype;
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_firsttime=true;
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}
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DHT::~DHT() {
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}
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int DHT::readData() {
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int i, j, retryCount,b;
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unsigned int bitTimes[DHT_DATA_BIT_COUNT];
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eError err = ERROR_NONE;
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time_t currentTime = time(NULL);
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DigitalInOut DHT_io(_pin);
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for (i = 0; i < DHT_DATA_BIT_COUNT; i++) {
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bitTimes[i] = 0;
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}
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if (!_firsttime) {
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if (int(currentTime - _lastReadTime) < 2) {
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err = ERROR_NO_PATIENCE;
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return err;
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}
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} else {
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_firsttime=false;
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_lastReadTime=currentTime;
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}
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retryCount = 0;
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do {
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if (retryCount > 125) {
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err = BUS_BUSY;
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return err;
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}
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retryCount ++;
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wait_us(2);
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} while ((DHT_io==0));
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DHT_io.output();
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DHT_io = 0;
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wait_ms(18);
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DHT_io = 1;
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wait_us(40);
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DHT_io.input();
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retryCount = 0;
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do {
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if (retryCount > 40) {
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err = ERROR_NOT_PRESENT;
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return err;
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}
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retryCount++;
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wait_us(1);
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} while ((DHT_io==1));
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if (err != ERROR_NONE) {
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return err;
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}
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wait_us(80);
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for (i = 0; i < 5; i++) {
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for (j = 0; j < 8; j++) {
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retryCount = 0;
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do {
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if (retryCount > 75) {
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err = ERROR_DATA_TIMEOUT;
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return err;
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}
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retryCount++;
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wait_us(1);
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} while (DHT_io == 0);
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wait_us(40);
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bitTimes[i*8+j]=DHT_io;
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int count = 0;
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while (DHT_io == 1 && count < 100) {
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wait_us(1);
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count++;
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}
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}
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}
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DHT_io.output();
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DHT_io = 1;
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for (i = 0; i < 5; i++) {
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b=0;
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for (j=0; j<8; j++) {
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if (bitTimes[i*8+j+1] > 0) {
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b |= ( 1 << (7-j));
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}
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}
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DHT_data[i]=b;
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}
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if (DHT_data[4] == ((DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]) & 0xFF)) {
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_lastReadTime = currentTime;
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_lastTemperature=CalcTemperature();
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_lastHumidity=CalcHumidity();
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} else {
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err = ERROR_CHECKSUM;
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}
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return err;
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}
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float DHT::CalcTemperature() {
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int v;
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switch (_DHTtype) {
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case DHT11:
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v = DHT_data[2];
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return float(v);
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case DHT22:
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v = DHT_data[2] & 0x7F;
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v *= 256;
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v += DHT_data[3];
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v /= 10;
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if (DHT_data[2] & 0x80)
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v *= -1;
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return float(v);
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}
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return 0;
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}
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float DHT::ReadHumidity() {
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return _lastHumidity;
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}
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float DHT::ConvertCelciustoFarenheit(float celsius) {
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return celsius * 9 / 5 + 32;
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}
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float DHT::ConvertCelciustoKelvin(float celsius) {
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return celsius + 273.15;
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}
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// dewPoint function NOAA
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// reference: http://wahiduddin.net/calc/density_algorithms.htm
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float DHT::CalcdewPoint(float celsius, float humidity) {
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float A0= 373.15/(273.15 + celsius);
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float SUM = -7.90298 * (A0-1);
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SUM += 5.02808 * log10(A0);
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SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
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SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
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SUM += log10(1013.246);
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float VP = pow(10, SUM-3) * humidity;
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float T = log(VP/0.61078); // temp var
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return (241.88 * T) / (17.558-T);
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}
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// delta max = 0.6544 wrt dewPoint()
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// 5x faster than dewPoint()
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// reference: http://en.wikipedia.org/wiki/Dew_point
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float DHT::CalcdewPointFast(float celsius, float humidity)
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{
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float a = 17.271;
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float b = 237.7;
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float temp = (a * celsius) / (b + celsius) + log(humidity/100);
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float Td = (b * temp) / (a - temp);
|
| Wimpie |
0:9b5b3200688f
|
204
|
return Td;
|
| Wimpie |
0:9b5b3200688f
|
205
|
}
|
| Wimpie |
0:9b5b3200688f
|
206
|
|
| Wimpie |
0:9b5b3200688f
|
207
|
float DHT::ReadTemperature(eScale Scale) {
|
| Wimpie |
0:9b5b3200688f
|
208
|
if (Scale == FARENHEIT)
|
| Wimpie |
0:9b5b3200688f
|
209
|
return ConvertCelciustoFarenheit(_lastTemperature);
|
| Wimpie |
0:9b5b3200688f
|
210
|
else if (Scale == KELVIN)
|
| Wimpie |
0:9b5b3200688f
|
211
|
return ConvertCelciustoKelvin(_lastTemperature);
|
| Wimpie |
0:9b5b3200688f
|
212
|
else
|
| Wimpie |
0:9b5b3200688f
|
213
|
return _lastTemperature;
|
| Wimpie |
0:9b5b3200688f
|
214
|
}
|
| Wimpie |
0:9b5b3200688f
|
215
|
|
| Wimpie |
0:9b5b3200688f
|
216
|
float DHT::CalcHumidity() {
|
| Wimpie |
0:9b5b3200688f
|
217
|
int v;
|
| Wimpie |
0:9b5b3200688f
|
218
|
|
| Wimpie |
0:9b5b3200688f
|
219
|
switch (_DHTtype) {
|
| Wimpie |
0:9b5b3200688f
|
220
|
case DHT11:
|
| Wimpie |
0:9b5b3200688f
|
221
|
v = DHT_data[0];
|
| Wimpie |
0:9b5b3200688f
|
222
|
return float(v);
|
| Wimpie |
0:9b5b3200688f
|
223
|
case DHT22:
|
| Wimpie |
0:9b5b3200688f
|
224
|
v = DHT_data[0];
|
| Wimpie |
0:9b5b3200688f
|
225
|
v *= 256;
|
| Wimpie |
0:9b5b3200688f
|
226
|
v += DHT_data[1];
|
| Wimpie |
0:9b5b3200688f
|
227
|
v /= 10;
|
| Wimpie |
0:9b5b3200688f
|
228
|
return float(v);
|
| Wimpie |
0:9b5b3200688f
|
229
|
}
|
| Wimpie |
0:9b5b3200688f
|
230
|
return 0;
|
| Wimpie |
0:9b5b3200688f
|
231
|
}
|
| Wimpie |
0:9b5b3200688f
|
232
|
|
| Wimpie |
0:9b5b3200688f
|
233
|
|