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+ masking unused bits (less errors);

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+ refactored bits[] usage
This commit is contained in:
rob tillaart 2014-10-15 07:48:27 +02:00
parent fa681d5322
commit 41cc579488
2 changed files with 19 additions and 9 deletions
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22
libraries/DHTlib/dht.cpp
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@ -1,11 +1,12 @@
// //
// FILE: dht.cpp // FILE: dht.cpp
// AUTHOR: Rob Tillaart // AUTHOR: Rob Tillaart
// VERSION: 0.1.15 // VERSION: 0.1.16
// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino // PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
// URL: http://arduino.cc/playground/Main/DHTLib // URL: http://arduino.cc/playground/Main/DHTLib
// //
// HISTORY: // HISTORY:
// 0.1.16 masking unused bits (less errors); refactored bits[]
// 0.1.15 reduced # micros calls 2->1 in inner loop. // 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. // 0.1.14 replace digital read with faster (~3x) code => more robust low MHz machines.
// 0.1.13 fix negative temperature // 0.1.13 fix negative temperature
@ -49,6 +50,9 @@ int dht::read11(uint8_t pin)
temperature = DHTLIB_INVALID_VALUE; temperature = DHTLIB_INVALID_VALUE;
return rv; return rv;
} }
// some bits are always zero, masking them reduces errors.
bits[0] &= 0x03;
bits[2] &= 0x83;
// CONVERT AND STORE // CONVERT AND STORE
humidity = bits[0]; // bits[1] == 0; humidity = bits[0]; // bits[1] == 0;
@ -79,6 +83,9 @@ int dht::read(uint8_t pin)
temperature = DHTLIB_INVALID_VALUE; // invalid value temperature = DHTLIB_INVALID_VALUE; // invalid value
return rv; // propagate error value return rv; // propagate error value
} }
// some bits are always zero, masking them reduces errors.
bits[0] &= 0x03;
bits[2] &= 0x83;
// CONVERT AND STORE // CONVERT AND STORE
humidity = word(bits[0], bits[1]) * 0.1; humidity = word(bits[0], bits[1]) * 0.1;
@ -118,9 +125,6 @@ int dht::_readSensor(uint8_t pin, uint8_t wakeupDelay)
uint8_t port = digitalPinToPort(pin); uint8_t port = digitalPinToPort(pin);
volatile uint8_t *PIR = portInputRegister(port); volatile uint8_t *PIR = portInputRegister(port);
// EMPTY BUFFER
for (uint8_t i = 0; i < 5; i++) bits[i] = 0;
// REQUEST SAMPLE // REQUEST SAMPLE
pinMode(pin, OUTPUT); pinMode(pin, OUTPUT);
digitalWrite(pin, LOW); // T-be digitalWrite(pin, LOW); // T-be
@ -150,6 +154,7 @@ int dht::_readSensor(uint8_t pin, uint8_t wakeupDelay)
if (--loopCount == 0) return DHTLIB_ERROR_TIMEOUT; if (--loopCount == 0) return DHTLIB_ERROR_TIMEOUT;
} }
uint8_t data = 0;
uint8_t state = LOW; uint8_t state = LOW;
uint8_t pstate = LOW; uint8_t pstate = LOW;
loopCount = DHTLIB_TIMEOUT; loopCount = DHTLIB_TIMEOUT;
@ -165,13 +170,15 @@ int dht::_readSensor(uint8_t pin, uint8_t wakeupDelay)
uint32_t t2 = micros(); uint32_t t2 = micros();
if ((t2-t1) > 100 ) // long -> one if ((t2-t1) > 100 ) // long -> one
{ {
bits[idx] |= mask; data |= mask;
} }
mask >>= 1; mask >>= 1;
if (mask == 0) // next byte if (mask == 0) // next byte
{ {
mask = 128; mask = 128;
bits[idx] = data;
idx++; idx++;
data = 0;
} }
// next bit // next bit
--i; --i;
@ -182,7 +189,10 @@ int dht::_readSensor(uint8_t pin, uint8_t wakeupDelay)
} }
pstate = state; pstate = state;
// Check timeout // Check timeout
if (--loopCount == 0) return DHTLIB_ERROR_TIMEOUT; if (--loopCount == 0)
{
return DHTLIB_ERROR_TIMEOUT;
}
} }
pinMode(pin, OUTPUT); pinMode(pin, OUTPUT);
digitalWrite(pin, HIGH); digitalWrite(pin, HIGH);

6
libraries/DHTlib/dht.h
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@ -1,7 +1,7 @@
// //
// FILE: dht.h // FILE: dht.h
// AUTHOR: Rob Tillaart // AUTHOR: Rob Tillaart
// VERSION: 0.1.15 // VERSION: 0.1.16
// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino // PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
// URL: http://arduino.cc/playground/Main/DHTLib // URL: http://arduino.cc/playground/Main/DHTLib
// //
@ -18,7 +18,7 @@
#include <Arduino.h> #include <Arduino.h>
#endif #endif
#define DHT_LIB_VERSION "0.1.15" #define DHT_LIB_VERSION "0.1.16"
#define DHTLIB_OK 0 #define DHTLIB_OK 0
#define DHTLIB_ERROR_CHECKSUM -1 #define DHTLIB_ERROR_CHECKSUM -1
@ -33,7 +33,7 @@
// loops using DHTLIB_TIMEOUT use at least 4 clock cycli // loops using DHTLIB_TIMEOUT use at least 4 clock cycli
// so 100 us takes max 400 loops // so 100 us takes max 400 loops
// so by dividing F_CPU by 40000 we "fail" as fast as possible // so by dividing F_CPU by 40000 we "fail" as fast as possible
#define DHTLIB_TIMEOUT (F_CPU/40000) #define DHTLIB_TIMEOUT 400 // (F_CPU/40000)
class dht class dht
{ {