Add hotfixed DHT.h

- Custom DHT.h correctly disables interrupts on ESP32, allowing for
conistent startup of sensor
- Closes hamishcunningham#15

ardesp/waterelf32/DHT.cpp

@@ -0,0 +1,259 @@
+/* DHT library
+
+MIT license
+written by Adafruit Industries
+*/
+
+#include "DHT.h"
+
+#define MIN_INTERVAL 2000
+
+DHT::DHT(uint8_t pin, uint8_t type, uint8_t count) {
+  _pin = pin;
+  _type = type;
+  #ifdef __AVR
+    _bit = digitalPinToBitMask(pin);
+    _port = digitalPinToPort(pin);
+  #endif
+  _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.
+}
+
+void DHT::begin(void) {
+  // set up the pins!
+  pinMode(_pin, INPUT_PULLUP);
+  // 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);
+}
+
+//boolean S == Scale.  True == Fahrenheit; False == Celcius
+float DHT::readTemperature(bool S, bool force) {
+  float f = NAN;
+
+  if (read(force)) {
+    switch (_type) {
+    case DHT11:
+      f = data[2];
+      if(S) {
+        f = convertCtoF(f);
+      }
+      break;
+    case DHT22:
+    case DHT21:
+      f = data[2] & 0x7F;
+      f *= 256;
+      f += data[3];
+      f *= 0.1;
+      if (data[2] & 0x80) {
+        f *= -1;
+      }
+      if(S) {
+        f = convertCtoF(f);
+      }
+      break;
+    }
+  }
+  return f;
+}
+
+float DHT::convertCtoF(float c) {
+  return c * 1.8 + 32;
+}
+
+float DHT::convertFtoC(float f) {
+  return (f - 32) * 0.55555;
+}
+
+float DHT::readHumidity(bool force) {
+  float f = NAN;
+  if (read()) {
+    switch (_type) {
+    case DHT11:
+      f = data[0];
+      break;
+    case DHT22:
+    case DHT21:
+      f = data[0];
+      f *= 256;
+      f += data[1];
+      f *= 0.1;
+      break;
+    }
+  }
+  return f;
+}
+
+//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;
+
+  if (!isFahrenheit)
+    temperature = convertCtoF(temperature);
+
+  hi = 0.5 * (temperature + 61.0 + ((temperature - 68.0) * 1.2) + (percentHumidity * 0.094));
+
+  if (hi > 79) {
+    hi = -42.379 +
+             2.04901523 * temperature +
+            10.14333127 * percentHumidity +
+            -0.22475541 * temperature*percentHumidity +
+            -0.00683783 * pow(temperature, 2) +
+            -0.05481717 * pow(percentHumidity, 2) +
+             0.00122874 * pow(temperature, 2) * percentHumidity +
+             0.00085282 * temperature*pow(percentHumidity, 2) +
+            -0.00000199 * pow(temperature, 2) * pow(percentHumidity, 2);
+
+    if((percentHumidity < 13) && (temperature >= 80.0) && (temperature <= 112.0))
+      hi -= ((13.0 - percentHumidity) * 0.25) * sqrt((17.0 - abs(temperature - 95.0)) * 0.05882);
+
+    else if((percentHumidity > 85.0) && (temperature >= 80.0) && (temperature <= 87.0))
+      hi += ((percentHumidity - 85.0) * 0.1) * ((87.0 - temperature) * 0.2);
+  }
+
+  return isFahrenheit ? hi : convertFtoC(hi);
+}
+
+boolean 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)) {
+    return _lastresult; // return last correct measurement
+  }
+  _lastreadtime = currenttime;
+
+  // Reset 40 bits of received data to zero.
+  data[0] = data[1] = data[2] = data[3] = data[4] = 0;
+
+  // Send start signal.  See DHT datasheet for full signal diagram:
+  //   http://www.adafruit.com/datasheets/Digital%20humidity%20and%20temperature%20sensor%20AM2302.pdf
+
+  // Go into high impedence state to let pull-up raise data line level and
+  // start the reading process.
+  digitalWrite(_pin, HIGH);
+  delay(250);
+
+  // First set data line low for 20 milliseconds.
+  pinMode(_pin, OUTPUT);
+  digitalWrite(_pin, LOW);
+  delay(20);
+
+  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);
+
+    // 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.
+
+    // 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."));
+      _lastresult = false;
+      return _lastresult;
+    }
+    if (expectPulse(HIGH) == 0) {
+      DEBUG_PRINTLN(F("Timeout waiting for start signal high pulse."));
+      _lastresult = false;
+      return _lastresult;
+    }
+
+    // Now read the 40 bits sent by the sensor.  Each bit is sent as a 50
+    // microsecond low pulse followed by a variable length high pulse.  If the
+    // high pulse is ~28 microseconds then it's a 0 and if it's ~70 microseconds
+    // then it's a 1.  We measure the cycle count of the initial 50us low pulse
+    // and use that to compare to the cycle count of the high pulse to determine
+    // if the bit is a 0 (high state cycle count < low state cycle count), or a
+    // 1 (high state cycle count > low state cycle count). Note that for speed all
+    // the pulses are read into a array and then examined in a later step.
+    for (int i=0; i<80; i+=2) {
+      cycles[i]   = expectPulse(LOW);
+      cycles[i+1] = expectPulse(HIGH);
+    }
+  } // Timing critical code is now complete.
+
+  // Inspect pulses and determine which ones are 0 (high state cycle count < low
+  // state cycle count), or 1 (high state cycle count > low state cycle count).
+  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."));
+      _lastresult = false;
+      return _lastresult;
+    }
+    data[i/8] <<= 1;
+    // Now compare the low and high cycle times to see if the bit is a 0 or 1.
+    if (highCycles > lowCycles) {
+      // High cycles are greater than 50us low cycle count, must be a 1.
+      data[i/8] |= 1;
+    }
+    // Else high cycles are less than (or equal to, a weird case) the 50us low
+    // cycle count so this must be a zero.  Nothing needs to be changed in the
+    // stored data.
+  }
+
+  DEBUG_PRINTLN(F("Received:"));
+  DEBUG_PRINT(data[0], HEX); DEBUG_PRINT(F(", "));
+  DEBUG_PRINT(data[1], HEX); DEBUG_PRINT(F(", "));
+  DEBUG_PRINT(data[2], HEX); DEBUG_PRINT(F(", "));
+  DEBUG_PRINT(data[3], HEX); DEBUG_PRINT(F(", "));
+  DEBUG_PRINT(data[4], HEX); DEBUG_PRINT(F(" =? "));
+  DEBUG_PRINTLN((data[0] + data[1] + data[2] + data[3]) & 0xFF, HEX);
+
+  // Check we read 40 bits and that the checksum matches.
+  if (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF)) {
+    _lastresult = true;
+    return _lastresult;
+  }
+  else {
+    DEBUG_PRINTLN(F("Checksum failure!"));
+    _lastresult = false;
+    return _lastresult;
+  }
+}
+
+// Expect the signal line to be at the specified level for a period of time and
+// return a count of loop cycles spent at that level (this cycle count can be
+// used to compare the relative time of two pulses).  If more than a millisecond
+// ellapses without the level changing then the call fails with a 0 response.
+// This is adapted from Arduino's pulseInLong function (which is only available
+// 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) {
+  uint32_t count = 0;
+  // 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.
+      }
+    }
+  // Otherwise fall back to using digitalRead (this seems to be necessary on ESP8266
+  // right now, perhaps bugs in direct port access functions?).
+  #else
+    while (digitalRead(_pin) == level) {
+      if (count++ >= _maxcycles) {
+        return 0; // Exceeded timeout, fail.
+      }
+    }
+  #endif
+
+  return count;
+}

ardesp/waterelf32/DHT.h

@@ -0,0 +1,82 @@
+/* DHT library
+
+MIT license
+written by Adafruit Industries
+*/
+#ifndef DHT_H
+#define DHT_H
+
+#if ARDUINO >= 100
+ #include "Arduino.h"
+#else
+ #include "WProgram.h"
+#endif
+
+
+// Uncomment to enable printing out nice debug messages.
+//#define DHT_DEBUG
+
+// Define where debug output will be printed.
+#define DEBUG_PRINTER Serial
+
+// Setup debug printing macros.
+#ifdef DHT_DEBUG
+  #define DEBUG_PRINT(...) { DEBUG_PRINTER.print(__VA_ARGS__); }
+  #define DEBUG_PRINTLN(...) { DEBUG_PRINTER.println(__VA_ARGS__); }
+#else
+  #define DEBUG_PRINT(...) {}
+  #define DEBUG_PRINTLN(...) {}
+#endif
+
+// Define types of sensors.
+#define DHT11 11
+#define DHT22 22
+#define DHT21 21
+#define AM2301 21
+
+
+class DHT {
+  public:
+   DHT(uint8_t pin, uint8_t type, uint8_t count=6);
+   void begin(void);
+   float readTemperature(bool S=false, bool force=false);
+   float convertCtoF(float);
+   float convertFtoC(float);
+   float computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit=true);
+   float readHumidity(bool force=false);
+   boolean read(bool force=false);
+
+ private:
+  uint8_t data[5];
+  uint8_t _pin, _type;
+  #ifdef __AVR
+    // Use direct GPIO access on an 8-bit AVR so keep track of the port and bitmask
+    // for the digital pin connected to the DHT.  Other platforms will use digitalRead.
+    uint8_t _bit, _port;
+  #endif
+  uint32_t _lastreadtime, _maxcycles;
+  bool _lastresult;
+
+  uint32_t expectPulse(bool level);
+
+};
+
+class InterruptLock {
+  public:
+   InterruptLock() {
+       #ifdef ESP32
+           taskDISABLE_INTERRUPTS();
+       #else
+           noInterrupts();
+       #endif
+   }
+   ~InterruptLock() {
+       #ifdef ESP32
+           taskENABLE_INTERRUPTS();
+       #else
+           interrupts();
+       #endif
+   }
+};
+
+#endif

ardesp/waterelf32/waterelf32.ino

@@ -5,7 +5,7 @@
 #include <ESPWebServer.h>
 #include <OneWire.h>
 #include <DallasTemperature.h>
-#include <DHT.h>
+#include "DHT.h"
 #include <Wire.h>
 #include <Adafruit_Sensor.h>
 #include <Adafruit_TSL2591.h>