Update library.properties

Fix for slower boards. Use uint16_t in expectPulse loop to increase sampling rate

DHT.cpp

@@ -7,6 +7,7 @@ written by Adafruit Industries
 #include "DHT.h"
 
 #define MIN_INTERVAL 2000
+#define TIMEOUT -1
 
 DHT::DHT(uint8_t pin, uint8_t type, uint8_t count) {
   _pin = pin;
@@ -18,7 +19,7 @@ DHT::DHT(uint8_t pin, uint8_t type, uint8_t count) {
   _maxcycles = microsecondsToClockCycles(1000);  // 1 millisecond timeout for
                                                  // reading pulses from DHT sensor.
   // Note that count is now ignored as the DHT reading algorithm adjusts itself
-  // basd on the speed of the processor.
+  // based on the speed of the processor.
 }
 
 void DHT::begin(void) {
@@ -27,8 +28,8 @@ void DHT::begin(void) {
   // Using this value makes sure that millis() - lastreadtime will be
   // >= MIN_INTERVAL right away. Note that this assignment wraps around,
   // but so will the subtraction.
-  _lastreadtime = -MIN_INTERVAL;
-  DEBUG_PRINT("Max clock cycles: "); DEBUG_PRINTLN(_maxcycles, DEC);
+  _lastreadtime = millis() - MIN_INTERVAL;
+  DEBUG_PRINT("DHT max clock cycles: "); DEBUG_PRINTLN(_maxcycles, DEC);
 }
 
 //boolean S == Scale.  True == Fahrenheit; False == Celcius
@@ -38,16 +39,19 @@ float DHT::readTemperature(bool S, bool force) {
   if (read(force)) {
     switch (_type) {
     case DHT11:
+    case DHT12:
       f = data[2];
+      f += (data[3] & 0x0f) * 0.1;
+      if (data[2] & 0x80) {
+        f *= -1;
+      }
       if(S) {
         f = convertCtoF(f);
       }
       break;
     case DHT22:
     case DHT21:
-      f = data[2] & 0x7F;
-      f *= 256;
-      f += data[3];
+      f = ((word)(data[2] & 0x7F)) << 8 | data[3];
       f *= 0.1;
       if (data[2] & 0x80) {
         f *= -1;
@@ -71,16 +75,15 @@ float DHT::convertFtoC(float f) {
 
 float DHT::readHumidity(bool force) {
   float f = NAN;
-  if (read()) {
+  if (read(force)) {
     switch (_type) {
     case DHT11:
-      f = data[0];
+    case DHT12:
+      f = data[0] + data[1] * 0.1;
       break;
     case DHT22:
     case DHT21:
-      f = data[0];
-      f *= 256;
-      f += data[1];
+      f = ((word)data[0]) << 8 | data[1];
       f *= 0.1;
       break;
     }
@@ -89,7 +92,15 @@ float DHT::readHumidity(bool force) {
 }
 
 //boolean isFahrenheit: True == Fahrenheit; False == Celcius
-float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit) {
+float DHT::computeHeatIndex(bool isFahrenheit) {
+  float hi = computeHeatIndex(readTemperature(isFahrenheit), readHumidity(),
+    isFahrenheit);
+  return isFahrenheit ? hi : convertFtoC(hi);
+}
+
+//boolean isFahrenheit: True == Fahrenheit; False == Celcius
+float DHT::computeHeatIndex(float temperature, float percentHumidity,
+  bool isFahrenheit) {
   // Using both Rothfusz and Steadman's equations
   // http://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml
   float hi;
@@ -120,11 +131,11 @@ float DHT::computeHeatIndex(float temperature, float percentHumidity, bool isFah
   return isFahrenheit ? hi : convertFtoC(hi);
 }
 
-boolean DHT::read(bool force) {
+bool DHT::read(bool force) {
   // Check if sensor was read less than two seconds ago and return early
   // to use last reading.
   uint32_t currenttime = millis();
-  if (!force && ((currenttime - _lastreadtime) < 2000)) {
+  if (!force && ((currenttime - _lastreadtime) < MIN_INTERVAL)) {
     return _lastresult; // return last correct measurement
   }
   _lastreadtime = currenttime;
@@ -137,37 +148,44 @@ boolean DHT::read(bool force) {
 
   // Go into high impedence state to let pull-up raise data line level and
   // start the reading process.
-  digitalWrite(_pin, HIGH);
-  delay(250);
+  pinMode(_pin, INPUT_PULLUP);
+  delay(1);
 
-  // First set data line low for 20 milliseconds.
+  // First set data line low for a period according to sensor type
   pinMode(_pin, OUTPUT);
   digitalWrite(_pin, LOW);
-  delay(20);
+  switch(_type) {
+    case DHT22: 
+    case DHT21: 
+      delayMicroseconds(1100); // data sheet says "at least 1ms"
+      break;
+    case DHT11:		 
+    default:
+      delay(20); //data sheet says at least 18ms, 20ms just to be safe
+      break;
+  }
 
   uint32_t cycles[80];
   {
-    // Turn off interrupts temporarily because the next sections are timing critical
-    // and we don't want any interruptions.
-    InterruptLock lock;
-
     // End the start signal by setting data line high for 40 microseconds.
-    digitalWrite(_pin, HIGH);
-    delayMicroseconds(40);
+    pinMode(_pin, INPUT_PULLUP);
 
     // Now start reading the data line to get the value from the DHT sensor.
-    pinMode(_pin, INPUT_PULLUP);
-    delayMicroseconds(10);  // Delay a bit to let sensor pull data line low.
+    delayMicroseconds(60);  // Delay a bit to let sensor pull data line low.
+
+    // Turn off interrupts temporarily because the next sections
+    // are timing critical and we don't want any interruptions.
+    InterruptLock lock;
 
     // First expect a low signal for ~80 microseconds followed by a high signal
     // for ~80 microseconds again.
-    if (expectPulse(LOW) == 0) {
-      DEBUG_PRINTLN(F("Timeout waiting for start signal low pulse."));
+    if (expectPulse(LOW) == TIMEOUT) {
+      DEBUG_PRINTLN(F("DHT timeout waiting for start signal low pulse."));
       _lastresult = false;
       return _lastresult;
     }
-    if (expectPulse(HIGH) == 0) {
-      DEBUG_PRINTLN(F("Timeout waiting for start signal high pulse."));
+    if (expectPulse(HIGH) == TIMEOUT) {
+      DEBUG_PRINTLN(F("DHT timeout waiting for start signal high pulse."));
       _lastresult = false;
       return _lastresult;
     }
@@ -191,8 +209,8 @@ boolean DHT::read(bool force) {
   for (int i=0; i<40; ++i) {
     uint32_t lowCycles  = cycles[2*i];
     uint32_t highCycles = cycles[2*i+1];
-    if ((lowCycles == 0) || (highCycles == 0)) {
-      DEBUG_PRINTLN(F("Timeout waiting for pulse."));
+    if ((lowCycles == TIMEOUT) || (highCycles == TIMEOUT)) {
+      DEBUG_PRINTLN(F("DHT timeout waiting for pulse."));
       _lastresult = false;
       return _lastresult;
     }
@@ -207,7 +225,7 @@ boolean DHT::read(bool force) {
     // stored data.
   }
 
-  DEBUG_PRINTLN(F("Received:"));
+  DEBUG_PRINTLN(F("Received from DHT:"));
   DEBUG_PRINT(data[0], HEX); DEBUG_PRINT(F(", "));
   DEBUG_PRINT(data[1], HEX); DEBUG_PRINT(F(", "));
   DEBUG_PRINT(data[2], HEX); DEBUG_PRINT(F(", "));
@@ -221,7 +239,7 @@ boolean DHT::read(bool force) {
     return _lastresult;
   }
   else {
-    DEBUG_PRINTLN(F("Checksum failure!"));
+    DEBUG_PRINTLN(F("DHT checksum failure!"));
     _lastresult = false;
     return _lastresult;
   }
@@ -235,14 +253,18 @@ boolean DHT::read(bool force) {
 // in the very latest IDE versions):
 //   https://github.com/arduino/Arduino/blob/master/hardware/arduino/avr/cores/arduino/wiring_pulse.c
 uint32_t DHT::expectPulse(bool level) {
+#if (F_CPU > 16000000L)
   uint32_t count = 0;
+#else
+  uint16_t count = 0; // To work fast enough on slower AVR boards
+#endif
   // On AVR platforms use direct GPIO port access as it's much faster and better
   // for catching pulses that are 10's of microseconds in length:
   #ifdef __AVR
     uint8_t portState = level ? _bit : 0;
     while ((*portInputRegister(_port) & _bit) == portState) {
       if (count++ >= _maxcycles) {
-        return 0; // Exceeded timeout, fail.
+        return TIMEOUT; // Exceeded timeout, fail.
       }
     }
   // Otherwise fall back to using digitalRead (this seems to be necessary on ESP8266
@@ -250,7 +272,7 @@ uint32_t DHT::expectPulse(bool level) {
   #else
     while (digitalRead(_pin) == level) {
       if (count++ >= _maxcycles) {
-        return 0; // Exceeded timeout, fail.
+        return TIMEOUT; // Exceeded timeout, fail.
       }
     }
   #endif

DHT.h

@@ -30,6 +30,7 @@ written by Adafruit Industries
 
 // Define types of sensors.
 #define DHT11 11
+#define DHT12 12
 #define DHT22 22
 #define DHT21 21
 #define AM2301 21
@@ -42,9 +43,10 @@ class DHT {
    float readTemperature(bool S=false, bool force=false);
    float convertCtoF(float);
    float convertFtoC(float);
+   float computeHeatIndex(bool isFahrenheit=true);
    float computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit=true);
    float readHumidity(bool force=false);
-   boolean read(bool force=false);
+   bool read(bool force=false);
 
  private:
   uint8_t data[5];
@@ -64,10 +66,14 @@ class DHT {
 class InterruptLock {
   public:
    InterruptLock() {
+#if !defined(ARDUINO_ARCH_NRF52)  
     noInterrupts();
+#endif
    }
    ~InterruptLock() {
+#if !defined(ARDUINO_ARCH_NRF52)  
     interrupts();
+#endif
    }
 
 };

DHT_U.cpp

@@ -37,6 +37,9 @@ void DHT_Unified::setName(sensor_t* sensor) {
     case DHT11:
       strncpy(sensor->name, "DHT11", sizeof(sensor->name) - 1);
       break;
+    case DHT12:
+      strncpy(sensor->name, "DHT12", sizeof(sensor->name) - 1);
+      break;
     case DHT21:
       strncpy(sensor->name, "DHT21", sizeof(sensor->name) - 1);
       break;
@@ -57,6 +60,9 @@ void DHT_Unified::setMinDelay(sensor_t* sensor) {
     case DHT11:
       sensor->min_delay = 1000000L;  // 1 second (in microseconds)
       break;
+    case DHT12:
+      sensor->min_delay = 2000000L;  // 2 second (in microseconds)
+      break;
     case DHT21:
       sensor->min_delay = 2000000L;  // 2 seconds (in microseconds)
       break;
@@ -105,6 +111,11 @@ void DHT_Unified::Temperature::getSensor(sensor_t* sensor) {
       sensor->min_value   = 0.0F;
       sensor->resolution  = 2.0F;
       break;
+    case DHT12:
+      sensor->max_value   = 60.0F;
+      sensor->min_value   = -20.0F;
+      sensor->resolution  = 0.5F;
+      break;
     case DHT21:
       sensor->max_value   = 80.0F;
       sensor->min_value   = -40.0F;
@@ -159,6 +170,11 @@ void DHT_Unified::Humidity::getSensor(sensor_t* sensor) {
       sensor->min_value   = 20.0F;
       sensor->resolution  = 5.0F;
       break;
+    case DHT12:
+      sensor->max_value   = 95.0F;
+      sensor->min_value   = 20.0F;
+      sensor->resolution  = 5.0F;
+      break;
     case DHT21:
       sensor->max_value   = 100.0F;
       sensor->min_value   = 0.0F;

examples/DHT_Unified_Sensor/DHT_Unified_Sensor.ino

@@ -11,12 +11,12 @@
 #include <DHT.h>
 #include <DHT_U.h>
 
-#define DHTPIN            2         // Pin which is connected to the DHT sensor.
+#define DHTPIN     2         // Pin connected to the DHT sensor.
 
 // Uncomment the type of sensor in use:
-//#define DHTTYPE           DHT11     // DHT 11 
-#define DHTTYPE           DHT22     // DHT 22 (AM2302)
-//#define DHTTYPE           DHT21     // DHT 21 (AM2301)
+//#define DHTTYPE    DHT11     // DHT 11
+#define DHTTYPE    DHT22     // DHT 22 (AM2302)
+//#define DHTTYPE    DHT21     // DHT 21 (AM2301)
 
 // See guide for details on sensor wiring and usage:
 //   https://learn.adafruit.com/dht/overview
@@ -26,33 +26,32 @@ DHT_Unified dht(DHTPIN, DHTTYPE);
 uint32_t delayMS;
 
 void setup() {
-  Serial.begin(9600); 
+  Serial.begin(9600);
   // Initialize device.
   dht.begin();
-  Serial.println("DHTxx Unified Sensor Example");
+  Serial.println(F("DHTxx Unified Sensor Example"));
   // Print temperature sensor details.
   sensor_t sensor;
   dht.temperature().getSensor(&sensor);
-  Serial.println("------------------------------------");
-  Serial.println("Temperature");
-  Serial.print  ("Sensor:       "); Serial.println(sensor.name);
-  Serial.print  ("Driver Ver:   "); Serial.println(sensor.version);
-  Serial.print  ("Unique ID:    "); Serial.println(sensor.sensor_id);
-  Serial.print  ("Max Value:    "); Serial.print(sensor.max_value); Serial.println(" *C");
-  Serial.print  ("Min Value:    "); Serial.print(sensor.min_value); Serial.println(" *C");
-  Serial.print  ("Resolution:   "); Serial.print(sensor.resolution); Serial.println(" *C");  
-  Serial.println("------------------------------------");
+  Serial.println(F("------------------------------------"));
+  Serial.println(F("Temperature Sensor"));
+  Serial.print  (F("Sensor Type: ")); Serial.println(sensor.name);
+  Serial.print  (F("Driver Ver:  ")); Serial.println(sensor.version);
+  Serial.print  (F("Unique ID:   ")); Serial.println(sensor.sensor_id);
+  Serial.print  (F("Max Value:   ")); Serial.print(sensor.max_value); Serial.println(F("°C"));
+  Serial.print  (F("Min Value:   ")); Serial.print(sensor.min_value); Serial.println(F("°C"));
+  Serial.print  (F("Resolution:  ")); Serial.print(sensor.resolution); Serial.println(F("°C"));
+  Serial.println(F("------------------------------------"));
   // Print humidity sensor details.
   dht.humidity().getSensor(&sensor);
-  Serial.println("------------------------------------");
-  Serial.println("Humidity");
-  Serial.print  ("Sensor:       "); Serial.println(sensor.name);
-  Serial.print  ("Driver Ver:   "); Serial.println(sensor.version);
-  Serial.print  ("Unique ID:    "); Serial.println(sensor.sensor_id);
-  Serial.print  ("Max Value:    "); Serial.print(sensor.max_value); Serial.println("%");
-  Serial.print  ("Min Value:    "); Serial.print(sensor.min_value); Serial.println("%");
-  Serial.print  ("Resolution:   "); Serial.print(sensor.resolution); Serial.println("%");  
-  Serial.println("------------------------------------");
+  Serial.println(F("Humidity Sensor"));
+  Serial.print  (F("Sensor Type: ")); Serial.println(sensor.name);
+  Serial.print  (F("Driver Ver:  ")); Serial.println(sensor.version);
+  Serial.print  (F("Unique ID:   ")); Serial.println(sensor.sensor_id);
+  Serial.print  (F("Max Value:   ")); Serial.print(sensor.max_value); Serial.println(F("%"));
+  Serial.print  (F("Min Value:   ")); Serial.print(sensor.min_value); Serial.println(F("%"));
+  Serial.print  (F("Resolution:  ")); Serial.print(sensor.resolution); Serial.println(F("%"));
+  Serial.println(F("------------------------------------"));
   // Set delay between sensor readings based on sensor details.
   delayMS = sensor.min_delay / 1000;
 }
@@ -61,24 +60,24 @@ void loop() {
   // Delay between measurements.
   delay(delayMS);
   // Get temperature event and print its value.
-  sensors_event_t event;  
+  sensors_event_t event;
   dht.temperature().getEvent(&event);
   if (isnan(event.temperature)) {
-    Serial.println("Error reading temperature!");
+    Serial.println(F("Error reading temperature!"));
   }
   else {
-    Serial.print("Temperature: ");
+    Serial.print(F("Temperature: "));
     Serial.print(event.temperature);
-    Serial.println(" *C");
+    Serial.println(F("°C"));
   }
   // Get humidity event and print its value.
   dht.humidity().getEvent(&event);
   if (isnan(event.relative_humidity)) {
-    Serial.println("Error reading humidity!");
+    Serial.println(F("Error reading humidity!"));
   }
   else {
-    Serial.print("Humidity: ");
+    Serial.print(F("Humidity: "));
     Serial.print(event.relative_humidity);
-    Serial.println("%");
+    Serial.println(F("%"));
   }
 }

examples/DHTtester/DHTtester.ino

@@ -25,7 +25,7 @@ DHT dht(DHTPIN, DHTTYPE);
 
 void setup() {
   Serial.begin(9600);
-  Serial.println("DHTxx test!");
+  Serial.println(F("DHTxx test!"));
 
   dht.begin();
 }
@@ -44,7 +44,7 @@ void loop() {
 
   // Check if any reads failed and exit early (to try again).
   if (isnan(h) || isnan(t) || isnan(f)) {
-    Serial.println("Failed to read from DHT sensor!");
+    Serial.println(F("Failed to read from DHT sensor!"));
     return;
   }
 
@@ -53,17 +53,15 @@ void loop() {
   // Compute heat index in Celsius (isFahreheit = false)
   float hic = dht.computeHeatIndex(t, h, false);
 
-  Serial.print("Humidity: ");
+  Serial.print(F("Humidity: "));
   Serial.print(h);
-  Serial.print(" %\t");
-  Serial.print("Temperature: ");
+  Serial.print(F("%  Temperature: "));
   Serial.print(t);
-  Serial.print(" *C ");
+  Serial.print(F("°C "));
   Serial.print(f);
-  Serial.print(" *F\t");
-  Serial.print("Heat index: ");
+  Serial.print(F("°F  Heat index: "));
   Serial.print(hic);
-  Serial.print(" *C ");
+  Serial.print(F("°C "));
   Serial.print(hif);
-  Serial.println(" *F");
+  Serial.println(F("°F"));
 }

keywords.txt

@@ -12,11 +12,11 @@ DHT	KEYWORD1
 # Methods and Functions (KEYWORD2)
 ###########################################
 
-begin KEYWORD2
-readTemperature KEYWORD2
-convertCtoF KEYWORD2
-convertFtoC KEYWORD2
-computeHeatIndex KEYWORD2
-readHumidity KEYWORD2
-read KEYWORD2
+begin	KEYWORD2
+readTemperature	KEYWORD2
+convertCtoF	KEYWORD2
+convertFtoC	KEYWORD2
+computeHeatIndex	KEYWORD2
+readHumidity	KEYWORD2
+read	KEYWORD2
 

library.properties

@@ -1,5 +1,5 @@
 name=DHT sensor library
-version=1.3.0
+version=1.3.1
 author=Adafruit
 maintainer=Adafruit <info@adafruit.com>
 sentence=Arduino library for DHT11, DHT22, etc Temp & Humidity Sensors