Diff: DHT.cpp

Revision:

3:fbe982025894

Parent:

2:df22ddf10d75

--- a/DHT.cpp	Fri Aug 15 20:55:43 2014 +0000
+++ b/DHT.cpp	Fri Mar 20 14:17:40 2015 +0000
@@ -9,7 +9,7 @@
  *
  *  Copyright (C) Wim De Roeve
  *                based on DHT22 sensor library by HO WING KIT
- *                Arduino DHT11 library
+ *                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
@@ -34,97 +34,110 @@
 
 #define DHT_DATA_BIT_COUNT 40
 
-DHT::DHT(PinName pin, eType DHTtype)
-{
+DHT::DHT(PinName pin,int DHTtype) {
     _pin = pin;
     _DHTtype = DHTtype;
-    _firsttime = true;
-}
-
-DHT::~DHT()
-{
-    
+    _firsttime=true;
 }
 
-eError DHT::stall(DigitalInOut &io, int const level, int const max_time)
-{
-    int cnt = 0;
-    while (level == io) {
-        if (cnt > max_time) {
-            return ERROR_NO_PATIENCE;
-        }
-        cnt++;
-        wait_us(1);
-    }
-    return ERROR_NONE;
+DHT::~DHT() {
 }
 
-eError DHT::readData()
-{
-    uint8_t i = 0, j = 0, b = 0, data_valid = 0;
-    uint32_t bit_value[DHT_DATA_BIT_COUNT] = {0};
+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);
 
-    // IO must be in hi state to start
-    if (ERROR_NONE != stall(DHT_io, 0, 250)) {
-        return BUS_BUSY;
+    for (i = 0; i < DHT_DATA_BIT_COUNT; i++) {
+        bitTimes[i] = 0;
     }
 
-    // start the transfer
+    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;
-    // only 500uS for DHT22 but 18ms for DHT11
-    (_DHTtype == 11) ? wait_ms(18) : wait(1);
+    wait_ms(18);
     DHT_io = 1;
-    wait_us(30);
+    wait_us(40);
     DHT_io.input();
-    // wait till the sensor grabs the bus
-    if (ERROR_NONE != stall(DHT_io, 1, 40)) {
-        return ERROR_NOT_PRESENT;
+
+    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;
     }
-    // sensor should signal low 80us and then hi 80us
-    if (ERROR_NONE != stall(DHT_io, 0, 100)) {
-        return ERROR_SYNC_TIMEOUT;
-    }
-    if (ERROR_NONE != stall(DHT_io, 1, 100)) {
-        return ERROR_NO_PATIENCE;
-    }
-    // capture the data
+
+    wait_us(80);
+
     for (i = 0; i < 5; i++) {
         for (j = 0; j < 8; j++) {
-            if (ERROR_NONE != stall(DHT_io, 0, 75)) {
-                return ERROR_DATA_TIMEOUT;
-            }
-            // logic 0 is 28us max, 1 is 70us
+
+            retryCount = 0;
+            do {
+                if (retryCount > 75)  {
+                    err = ERROR_DATA_TIMEOUT;
+                    return err;
+                }
+                retryCount++;
+                wait_us(1);
+            } while (DHT_io == 0);
             wait_us(40);
-            bit_value[i*8+j] = DHT_io;
-            if (ERROR_NONE != stall(DHT_io, 1, 50)) {
-                return ERROR_DATA_TIMEOUT;
+            bitTimes[i*8+j]=DHT_io;
+
+            int count = 0;
+            while (DHT_io == 1 && count < 100) {
+                wait_us(1);
+                count++;
             }
         }
     }
-    // store the data
+    DHT_io.output();
+    DHT_io = 1;
     for (i = 0; i < 5; i++) {
         b=0;
         for (j=0; j<8; j++) {
-            if (bit_value[i*8+j] == 1) {
-                b |= (1 << (7-j));
+            if (bitTimes[i*8+j+1] > 0) {
+                b |= ( 1 << (7-j));
             }
         }
         DHT_data[i]=b;
     }
 
-    // uncomment to see the checksum error if it exists
-    //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]);
-    data_valid = DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3];
-    if (DHT_data[4] == data_valid) {
+    if (DHT_data[4] == ((DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]) & 0xFF)) {
         _lastReadTime = currentTime;
-        _lastTemperature = CalcTemperature();
-        _lastHumidity = CalcHumidity();
+        _lastTemperature=CalcTemperature();
+        _lastHumidity=CalcHumidity();
 
     } else {
         err = ERROR_CHECKSUM;
@@ -134,8 +147,7 @@
 
 }
 
-float DHT::CalcTemperature()
-{
+float DHT::CalcTemperature() {
     int v;
 
     switch (_DHTtype) {
@@ -154,25 +166,21 @@
     return 0;
 }
 
-float DHT::ReadHumidity()
-{
+float DHT::ReadHumidity() {
     return _lastHumidity;
 }
 
-float DHT::ConvertCelciustoFarenheit(float const celsius)
-{
+float DHT::ConvertCelciustoFarenheit(float celsius) {
     return celsius * 9 / 5 + 32;
 }
 
-float DHT::ConvertCelciustoKelvin(float const celsius)
-{
+float DHT::ConvertCelciustoKelvin(float celsius) {
     return celsius + 273.15;
 }
 
 // dewPoint function NOAA
 // reference: http://wahiduddin.net/calc/density_algorithms.htm
-float DHT::CalcdewPoint(float const celsius, float const humidity)
-{
+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);
@@ -187,17 +195,16 @@
 // delta max = 0.6544 wrt dewPoint()
 // 5x faster than dewPoint()
 // reference: http://en.wikipedia.org/wiki/Dew_point
-float DHT::CalcdewPointFast(float const celsius, float const humidity)
+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 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)
-{
+float DHT::ReadTemperature(eScale Scale) {
     if (Scale == FARENHEIT)
         return ConvertCelciustoFarenheit(_lastTemperature);
     else if (Scale == KELVIN)
@@ -206,8 +213,7 @@
         return _lastTemperature;
 }
 
-float DHT::CalcHumidity()
-{
+float DHT::CalcHumidity() {
     int v;
 
     switch (_DHTtype) {