+ reduced # micros calls 2->1 in inner loop. => footprint -18

 detection of the zero/one is doen by measuring the whole bit LOW+HIGH + improved wait for acknowledge + merged two loopCounters into one. + layout + dht22_test sketch collects statistics (every 20 reads)

Author: RobTillaart

libraries/DHTlib/dht.cpp

@@ -1,11 +1,12 @@
 //
 // FILE: dht.cpp
 // AUTHOR: Rob Tillaart
-// VERSION: 0.1.14
+// VERSION: 0.1.15
 // PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
 // URL: http://arduino.cc/playground/Main/DHTLib
 //
 // HISTORY:
+// 0.1.15 reduced # micros calls 2->1 in inner loop.
 // 0.1.14 replace digital read with faster (~3x) code => more robust low MHz machines.
 // 0.1.13 fix negative temperature
 // 0.1.12 support DHT33 and DHT44 initial version
@@ -44,8 +45,8 @@ int dht::read11(uint8_t pin)
  int rv = _readSensor(pin, DHTLIB_DHT11_WAKEUP);
  if (rv != DHTLIB_OK)
  {
- humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
- temperature = DHTLIB_INVALID_VALUE; // invalid value
+ humidity = DHTLIB_INVALID_VALUE;
+ temperature = DHTLIB_INVALID_VALUE;
  return rv;
  }
 
@@ -56,8 +57,10 @@ int dht::read11(uint8_t pin)
  // TEST CHECKSUM
  // bits[1] && bits[3] both 0
  uint8_t sum = bits[0] + bits[2];
- if (bits[4] != sum) return DHTLIB_ERROR_CHECKSUM;
-
+ if (bits[4] != sum)
+ {
+ return DHTLIB_ERROR_CHECKSUM;
+ }
  return DHTLIB_OK;
 }
 
@@ -111,61 +114,75 @@ int dht::_readSensor(uint8_t pin, uint8_t wakeupDelay)
  // replace digitalRead() with Direct Port Reads.
  // reduces footprint ~100 bytes => portability issue?
  // direct port read is about 3x faster
-uint8_t bit = digitalPinToBitMask(pin);
-uint8_t port = digitalPinToPort(pin);
+ uint8_t bit = digitalPinToBitMask(pin);
+ uint8_t port = digitalPinToPort(pin);
  volatile uint8_t *PIR = portInputRegister(port);
 
  // EMPTY BUFFER
  for (uint8_t i = 0; i < 5; i++) bits[i] = 0;
 
  // REQUEST SAMPLE
  pinMode(pin, OUTPUT);
- digitalWrite(pin, LOW); // T-be 
+ digitalWrite(pin, LOW); // T-be
  delay(wakeupDelay);
- digitalWrite(pin, HIGH); // T-go
- delayMicroseconds(40);
+ digitalWrite(pin, HIGH); // T-go
  pinMode(pin, INPUT);
 
+ uint16_t loopCount = DHTLIB_TIMEOUT*2; // 200uSec max
+ // while(digitalRead(pin) == HIGH)
+ while ((*PIR & bit) != LOW )
+ {
+ if (--loopCount == 0) return DHTLIB_ERROR_TIMEOUT;
+ }
+
  // GET ACKNOWLEDGE or TIMEOUT
- uint16_t loopCntLOW = DHTLIB_TIMEOUT;
+ loopCount = DHTLIB_TIMEOUT;
+ // while(digitalRead(pin) == LOW)
  while ((*PIR & bit) == LOW ) // T-rel
  {
- if (--loopCntLOW == 0) return DHTLIB_ERROR_TIMEOUT;
+ if (--loopCount == 0) return DHTLIB_ERROR_TIMEOUT;
  }
 
- uint16_t loopCntHIGH = DHTLIB_TIMEOUT;
+ loopCount = DHTLIB_TIMEOUT;
+ // while(digitalRead(pin) == HIGH)
  while ((*PIR & bit) != LOW ) // T-reh
  {
- if (--loopCntHIGH == 0) return DHTLIB_ERROR_TIMEOUT;
+ if (--loopCount == 0) return DHTLIB_ERROR_TIMEOUT;
  }
 
+ uint8_t state = LOW;
+ uint8_t pstate = LOW;
+ loopCount = DHTLIB_TIMEOUT;
+ uint32_t t1 = micros();
+
  // READ THE OUTPUT - 40 BITS => 5 BYTES
- for (uint8_t i = 40; i != 0; i--)
+ for (uint8_t i = 40; i != 0; )
  {
- loopCntLOW = DHTLIB_TIMEOUT;
- while ((*PIR & bit) == LOW )
- {
- if (--loopCntLOW == 0) return DHTLIB_ERROR_TIMEOUT;
- }
-
- uint32_t t = micros();
- 
- loopCntHIGH = DHTLIB_TIMEOUT;
- while ((*PIR & bit) != LOW )
- {
- if (--loopCntHIGH == 0) return DHTLIB_ERROR_TIMEOUT;
- }
-
- if ((micros() - t) > 40)
- { 
- bits[idx] |= mask;
- }
- mask >>= 1;
- if (mask == 0) // next byte?
+ // WAIT FOR FALLING EDGE
+ state = (*PIR & bit);
+ if (state == LOW && pstate != LOW)
  {
- mask = 128;
- idx++;
+ uint32_t t2 = micros();
+ if ((t2-t1) > 100 ) // long -> one
+ {
+ bits[idx] |= mask;
+ }
+ mask >>= 1;
+ if (mask == 0) // next byte
+ {
+ mask = 128;
+ idx++;
+ }
+ // next bit
+ --i;
+ // update time admin
+ t1 = t2;
+ // reset timeout flag
+ loopCount = DHTLIB_TIMEOUT;
  }
+ pstate = state;
+ // Check timeout
+ if (--loopCount == 0) return DHTLIB_ERROR_TIMEOUT;
  }
  pinMode(pin, OUTPUT);
  digitalWrite(pin, HIGH);

libraries/DHTlib/dht.h

@@ -1,7 +1,7 @@
 //
 // FILE: dht.h
 // AUTHOR: Rob Tillaart
-// VERSION: 0.1.14
+// VERSION: 0.1.15
 // PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
 // URL: http://arduino.cc/playground/Main/DHTLib
 //
@@ -18,7 +18,7 @@
 #include <Arduino.h>
 #endif
 
-#define DHT_LIB_VERSION "0.1.14"
+#define DHT_LIB_VERSION "0.1.15"
 
 #define DHTLIB_OK 0
 #define DHTLIB_ERROR_CHECKSUM -1

libraries/DHTlib/examples/dht22_test/dht22_test.ino

@@ -1,9 +1,13 @@
 //
 // FILE: dht22_test.ino
 // AUTHOR: Rob Tillaart
-// VERSION: 0.1.01
+// VERSION: 0.1.02
 // PURPOSE: DHT library test sketch for DHT22 && Arduino
 // URL:
+// HISTORY: 
+// 0.1.02 added counters for error-regression testing.
+// 0.1.01 
+// 0.1.00 initial version
 //
 // Released to the public domain
 //
@@ -14,10 +18,19 @@ dht DHT;
 
 #define DHT22_PIN 5
 
+struct
+{
+ uint32_t total;
+ uint32_t ok;
+ uint32_t crc_error;
+ uint32_t time_out;
+ uint32_t unknown;
+} stat = { 0,0,0,0,0 };
+
 void setup()
 {
  Serial.begin(115200);
- Serial.println("DHT TEST PROGRAM ");
+ Serial.println("dht22_test.ino");
  Serial.print("LIBRARY VERSION: ");
  Serial.println(DHT_LIB_VERSION);
  Serial.println();
@@ -33,18 +46,23 @@ void loop()
  int chk = DHT.read22(DHT22_PIN);
  uint32_t stop = micros();
 
+ stat.total++;
  switch (chk)
  {
  case DHTLIB_OK:
+ stat.ok++;
  Serial.print("OK,\t");
  break;
  case DHTLIB_ERROR_CHECKSUM:
+ stat.crc_error++;
  Serial.print("Checksum error,\t");
  break;
  case DHTLIB_ERROR_TIMEOUT:
+ stat.time_out++;
  Serial.print("Time out error,\t");
  break;
  default:
+ stat.unknown++;
  Serial.print("Unknown error,\t");
  break;
  }
@@ -56,6 +74,20 @@ void loop()
  Serial.print(stop - start);
  Serial.println();
 
+ if (stat.total % 20 == 0)
+ {
+ Serial.println("\nTOT\tOK\tCRC\tTO\tUNK");
+ Serial.print(stat.total);
+ Serial.print("\t");
+ Serial.print(stat.ok);
+ Serial.print("\t");
+ Serial.print(stat.crc_error);
+ Serial.print("\t");
+ Serial.print(stat.time_out);
+ Serial.print("\t");
+ Serial.print(stat.unknown);
+ Serial.println("\n");
+ }
  delay(2000);
 }
 //