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optimized wakeup and timeout

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rob tillaart 2014-06-01 09:48:06 +02:00
parent 1f8c5f06bb
commit 1f2314cdbf
2 changed files with 39 additions and 27 deletions
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48
libraries/DHTlib/dht.cpp
View File

@ -1,11 +1,12 @@
//
// FILE: dht.cpp
// AUTHOR: Rob Tillaart
// VERSION: 0.1.09
// VERSION: 0.1.10
// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
// URL: http://arduino.cc/playground/Main/DHTLib
//
// HISTORY:
// 0.1.10 optimized faster WAKEUP + TIMEOUT
// 0.1.09 optimize size: timeout check + use of mask
// 0.1.08 added formula for timeout based upon clockspeed
// 0.1.07 added support for DHT21
@ -24,13 +25,12 @@
#include "dht.h"
// #define TIMEOUT 10000
// uint16_t for UNO, higher CPU speeds => exceed MAXINT.
// works for DUE
// 16 MHz => 10000
// 84 MHz => 52500
// 100MHz => 62500
#define TIMEOUT (F_CPU/1600)
// max timeout is 100usec.
// For a 16Mhz proc that is max 1600 clock cycles
// loops using TIMEOUT use at least 4 clock cycli
// so 100 us takes max 400 loops
// so by dividing F_CPU by 40000 we "fail" as fast as possible
#define TIMEOUT (F_CPU/40000)
/////////////////////////////////////////////////////
@ -45,7 +45,7 @@
int dht::read11(uint8_t pin)
{
// READ VALUES
int rv = read(pin);
int rv = read(pin, DHTLIB_DHT11_WAKEUP);
if (rv != DHTLIB_OK)
{
humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
@ -71,7 +71,8 @@ int dht::read11(uint8_t pin)
// DHTLIB_ERROR_TIMEOUT
int dht::read21(uint8_t pin)
{
return read22(pin); // dataformat identical to DHT22
// dataformat & wakeup identical to DHT22
return read22(pin);
}
// return values:
@ -81,7 +82,7 @@ int dht::read21(uint8_t pin)
int dht::read22(uint8_t pin)
{
// READ VALUES
int rv = read(pin);
int rv = read(pin, DHTLIB_DHT22_WAKEUP);
if (rv != DHTLIB_OK)
{
humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
@ -116,19 +117,19 @@ int dht::read22(uint8_t pin)
// return values:
// DHTLIB_OK
// DHTLIB_ERROR_TIMEOUT
int dht::read(uint8_t pin)
int dht::read(uint8_t pin, uint8_t wakeupDelay)
{
// INIT BUFFERVAR TO RECEIVE DATA
uint8_t mask = 128;
uint8_t idx = 0;
// EMPTY BUFFER
for (uint8_t i=0; i< 5; i++) bits[i] = 0;
for (uint8_t i = 0; i < 5; i++) bits[i] = 0;
// REQUEST SAMPLE
pinMode(pin, OUTPUT);
digitalWrite(pin, LOW);
delay(20);
delay(wakeupDelay);
digitalWrite(pin, HIGH);
delayMicroseconds(40);
pinMode(pin, INPUT);
@ -136,24 +137,32 @@ int dht::read(uint8_t pin)
// GET ACKNOWLEDGE or TIMEOUT
unsigned int loopCnt = TIMEOUT;
while(digitalRead(pin) == LOW)
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
{
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
}
loopCnt = TIMEOUT;
while(digitalRead(pin) == HIGH)
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
{
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
}
// READ THE OUTPUT - 40 BITS => 5 BYTES
for (uint8_t i=0; i<40; i++)
for (uint8_t i = 0; i < 40; i++)
{
loopCnt = TIMEOUT;
while(digitalRead(pin) == LOW)
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
{
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
}
unsigned long t = micros();
loopCnt = TIMEOUT;
while(digitalRead(pin) == HIGH)
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
{
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
}
if ((micros() - t) > 40) bits[idx] |= mask;
mask >>= 1;
@ -163,7 +172,6 @@ int dht::read(uint8_t pin)
idx++;
}
}
return DHTLIB_OK;
}
//

18
libraries/DHTlib/dht.h
View File

@ -1,7 +1,7 @@
//
// FILE: dht.h
// AUTHOR: Rob Tillaart
// VERSION: 0.1.09
// VERSION: 0.1.10
// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
// URL: http://arduino.cc/playground/Main/DHTLib
//
@ -18,12 +18,16 @@
#include <Arduino.h>
#endif
#define DHT_LIB_VERSION "0.1.09"
#define DHT_LIB_VERSION "0.1.10"
#define DHTLIB_OK 0
#define DHTLIB_ERROR_CHECKSUM -1
#define DHTLIB_ERROR_TIMEOUT -2
#define DHTLIB_INVALID_VALUE -999
#define DHTLIB_DHT11_WAKEUP 18
#define DHTLIB_DHT22_WAKEUP 1
#define DHTLIB_OK 0
#define DHTLIB_ERROR_CHECKSUM -1
#define DHTLIB_ERROR_TIMEOUT -2
#define DHTLIB_INVALID_VALUE -999
class dht
{
@ -37,7 +41,7 @@ public:
private:
uint8_t bits[5]; // buffer to receive data
int read(uint8_t pin);
int read(uint8_t pin, uint8_t wakeupDelay);
};
#endif
//