Diff: DHT.cpp

Revision:

0:9b5b3200688f

Child:

1:6ddabfde1db6

diff -r 000000000000 -r 9b5b3200688f DHT.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/DHT.cpp	Mon Jul 09 19:47:43 2012 +0000
@@ -0,0 +1,233 @@
+/*
+ *  DHT Library for  Digital-output Humidity and Temperature sensors
+ *
+ *  Works with DHT11, DHT22
+ *             SEN11301P,  Grove - Temperature&Humidity Sensor     (Seeed Studio)
+ *             SEN51035P,  Grove - Temperature&Humidity Sensor Pro (Seeed Studio)
+ *             AM2302   ,  temperature-humidity sensor
+ *             HM2303   ,  Digital-output humidity and temperature sensor
+ *
+ *  Copyright (C) Wim De Roeve
+ *                based on DHT22 sensor library by HO WING KIT
+ *                Arduino DHT11 library 
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documnetation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to  whom the Software is
+ * furished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS OR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "DHT.h"
+
+#define DHT_DATA_BIT_COUNT 41
+
+DHT::DHT(PinName pin,int DHTtype) {
+    _pin = pin;
+    _DHTtype = DHTtype;
+    _firsttime=true;
+}
+
+DHT::~DHT() {
+}
+
+int DHT::readData() {
+    int i, j, retryCount,b;
+    unsigned int bitTimes[DHT_DATA_BIT_COUNT];
+
+    eError err = ERROR_NONE;
+    time_t currentTime = time(NULL);
+
+    DigitalInOut DHT_io(_pin);
+
+    for (i = 0; i < DHT_DATA_BIT_COUNT; i++) {
+        bitTimes[i] = 0;
+    }
+
+    if (!_firsttime) {
+        if (int(currentTime - _lastReadTime) < 2) {
+            err = ERROR_NO_PATIENCE;
+            return err;
+        }
+    } else {
+        _firsttime=false;
+        _lastReadTime=currentTime;
+    }
+    retryCount = 0;
+
+    do {
+        if (retryCount > 125) {
+            err = BUS_BUSY;
+            return err;
+        }
+        retryCount ++;
+        wait_us(2);
+    } while ((DHT_io==0));
+
+
+    DHT_io.output();
+    DHT_io = 0;
+    wait_ms(18);
+    DHT_io = 1;
+    wait_us(40);
+    DHT_io.input();
+
+    retryCount = 0;
+    do {
+        if (retryCount > 40)  {
+            err = ERROR_NOT_PRESENT;
+            return err;
+        }
+        retryCount++;
+        wait_us(1);
+    } while ((DHT_io==1));
+
+    if (err != ERROR_NONE) {
+        return err;
+    }
+
+    wait_us(80);
+
+    for (i = 0; i < 5; i++) {
+        for (j = 0; j < 8; j++) {
+
+            retryCount = 0;
+            do {
+                if (retryCount > 75)  {
+                    err = ERROR_DATA_TIMEOUT;
+                    return err;
+                }
+                retryCount++;
+                wait_us(1);
+            } while (DHT_io == 0);
+            wait_us(40);
+            bitTimes[i*8+j]=DHT_io;
+
+            int count = 0;
+            while (DHT_io == 1 && count < 100) {
+                wait_us(1);
+                count++;
+            }
+        }
+    }
+    DHT_io.output();
+    DHT_io = 1;
+    for (i = 0; i < 5; i++) {
+        b=0;
+        for (j=0; j<8; j++) {
+            if (bitTimes[i*8+j+1] > 0) {
+                b |= ( 1 << (7-j));
+            }
+        }
+        DHT_data[i]=b;
+    }
+
+    if (DHT_data[4] == ((DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]) & 0xFF)) {
+        _lastReadTime = currentTime;
+        _lastTemperature=CalcTemperature();
+        _lastHumidity=CalcHumidity();
+
+    } else {
+        err = ERROR_CHECKSUM;
+    }
+
+    return err;
+
+}
+
+float DHT::CalcTemperature() {
+    int v;
+
+    switch (_DHTtype) {
+        case DHT11:
+            v = DHT_data[2];
+            return float(v);
+        case DHT22:
+            v = DHT_data[2] & 0x7F;
+            v *= 256;
+            v += DHT_data[3];
+            v /= 10;
+            if (DHT_data[2] & 0x80)
+                v *= -1;
+            return float(v);
+    }
+    return 0;
+}
+
+float DHT::ReadHumidity() {
+    return _lastHumidity;
+}
+
+float DHT::ConvertCelciustoFarenheit(float celsius) {
+    return celsius * 9 / 5 + 32;
+}
+
+float DHT::ConvertCelciustoKelvin(float celsius) {
+    return celsius + 273.15;
+}
+
+// dewPoint function NOAA
+// reference: http://wahiduddin.net/calc/density_algorithms.htm
+float DHT::CalcdewPoint(float celsius, float humidity) {
+    float A0= 373.15/(273.15 + celsius);
+    float SUM = -7.90298 * (A0-1);
+    SUM += 5.02808 * log10(A0);
+    SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ;
+    SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ;
+    SUM += log10(1013.246);
+    float VP = pow(10, SUM-3) * humidity;
+    float T = log(VP/0.61078);   // temp var
+    return (241.88 * T) / (17.558-T);
+}
+
+// delta max = 0.6544 wrt dewPoint()
+// 5x faster than dewPoint()
+// reference: http://en.wikipedia.org/wiki/Dew_point
+float DHT::CalcdewPointFast(float celsius, float humidity)
+{
+        float a = 17.271;
+        float b = 237.7;
+        float temp = (a * celsius) / (b + celsius) + log(humidity/100);
+        float Td = (b * temp) / (a - temp);
+        return Td;
+}
+
+float DHT::ReadTemperature(eScale Scale) {
+    if (Scale == FARENHEIT)
+        return ConvertCelciustoFarenheit(_lastTemperature);
+    else if (Scale == KELVIN)
+        return ConvertCelciustoKelvin(_lastTemperature);
+    else
+        return _lastTemperature;
+}
+
+float DHT::CalcHumidity() {
+    int v;
+
+    switch (_DHTtype) {
+        case DHT11:
+            v = DHT_data[0];
+            return float(v);
+        case DHT22:
+            v = DHT_data[0];
+            v *= 256;
+            v += DHT_data[1];
+            v /= 10;
+            return float(v);
+    }
+    return 0;
+}
+
+