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ebd147b34f
* DHT11 read sometimes failed with checksum error. The code assumed DHT11 devices only ever return zero in the temperature and humidity decimal fraction bytes. The datasheet doesn't guarantee this is the case, and by observation I have noticed that indeed the DHT11 may sometimes return another number, usually close to zero. This means that the code would fail with a checksum error, as the fraction bytes were not included when the checksum was calculated. These bytes are now taken into account and also returned as part of the measurement. This also means that the related dht.read() function is non-functional. If you have a DHT11 device that returns a non-zero decimal part, dht.read() will interpret it as a DHT22 result and return the wrong measurement. For this reason dht.read() should be retired. This patch does not address this issue.
320 lines
8.4 KiB
C
320 lines
8.4 KiB
C
//
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// FILE: dht.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.14
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// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
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// URL: http://arduino.cc/playground/Main/DHTLib
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//
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// HISTORY:
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// 0.1.14 replace digital read with faster (~3x) code => more robust low MHz machines.
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// 0.1.13 fix negative dht_temperature
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// 0.1.12 support DHT33 and DHT44 initial version
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// 0.1.11 renamed DHTLIB_TIMEOUT
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// 0.1.10 optimized faster WAKEUP + TIMEOUT
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// 0.1.09 optimize size: timeout check + use of mask
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// 0.1.08 added formula for timeout based upon clockspeed
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// 0.1.07 added support for DHT21
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// 0.1.06 minimize footprint (2012-12-27)
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// 0.1.05 fixed negative dht_temperature bug (thanks to Roseman)
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// 0.1.04 improved readability of code using DHTLIB_OK in code
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// 0.1.03 added error values for temp and dht_humidity when read failed
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// 0.1.02 added error codes
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// 0.1.01 added support for Arduino 1.0, fixed typos (31/12/2011)
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// 0.1.00 by Rob Tillaart (01/04/2011)
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//
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// inspired by DHT11 library
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//
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// Released to the public domain
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//
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#include "user_interface.h"
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#include "platform.h"
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#include "c_stdio.h"
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#include "dht.h"
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#ifndef LOW
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#define LOW 0
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#endif /* ifndef LOW */
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#ifndef HIGH
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#define HIGH 1
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#endif /* ifndef HIGH */
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#define COMBINE_HIGH_AND_LOW_BYTE(byte_high, byte_low) (((byte_high) << 8) | (byte_low))
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static double dht_humidity;
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static double dht_temperature;
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static uint8_t dht_bytes[5]; // buffer to receive data
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static int dht_readSensor(uint8_t pin, uint8_t wakeupDelay);
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/////////////////////////////////////////////////////
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//
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// PUBLIC
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//
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// return values:
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// Humidity
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double dht_getHumidity(void)
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{
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return dht_humidity;
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}
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// return values:
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// Temperature
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double dht_getTemperature(void)
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{
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return dht_temperature;
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}
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_CHECKSUM
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// DHTLIB_ERROR_TIMEOUT
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int dht_read_universal(uint8_t pin)
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{
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// READ VALUES
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int rv = dht_readSensor(pin, DHTLIB_DHT_UNI_WAKEUP);
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if (rv != DHTLIB_OK)
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{
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dht_humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
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dht_temperature = DHTLIB_INVALID_VALUE; // invalid value
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return rv; // propagate error value
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}
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#if defined(DHT_DEBUG_BYTES)
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int i;
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for (i = 0; i < 5; i++)
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{
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DHT_DEBUG("%02X\n", dht_bytes[i]);
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}
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#endif // defined(DHT_DEBUG_BYTES)
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// Assume it is DHT11
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// If it is DHT11, both bit[1] and bit[3] is 0
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if ((dht_bytes[1] == 0) && (dht_bytes[3] == 0))
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{
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// It may DHT11
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// CONVERT AND STORE
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DHT_DEBUG("DHT11 method\n");
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dht_humidity = dht_bytes[0]; // dht_bytes[1] == 0;
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dht_temperature = dht_bytes[2]; // dht_bytes[3] == 0;
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// TEST CHECKSUM
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// dht_bytes[1] && dht_bytes[3] both 0
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uint8_t sum = dht_bytes[0] + dht_bytes[2];
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if (dht_bytes[4] != sum)
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{
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// It may not DHT11
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dht_humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
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dht_temperature = DHTLIB_INVALID_VALUE; // invalid value
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// Do nothing
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}
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else
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{
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return DHTLIB_OK;
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}
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}
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// Assume it is not DHT11
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// CONVERT AND STORE
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DHT_DEBUG("DHTxx method\n");
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dht_humidity = (double)COMBINE_HIGH_AND_LOW_BYTE(dht_bytes[0], dht_bytes[1]) * 0.1;
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dht_temperature = (double)COMBINE_HIGH_AND_LOW_BYTE(dht_bytes[2] & 0x7F, dht_bytes[3]) * 0.1;
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if (dht_bytes[2] & 0x80) // negative dht_temperature
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{
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dht_temperature = -dht_temperature;
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}
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// TEST CHECKSUM
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uint8_t sum = dht_bytes[0] + dht_bytes[1] + dht_bytes[2] + dht_bytes[3];
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if (dht_bytes[4] != sum)
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{
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return DHTLIB_ERROR_CHECKSUM;
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}
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return DHTLIB_OK;
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}
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_CHECKSUM
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// DHTLIB_ERROR_TIMEOUT
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int dht_read11(uint8_t pin)
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{
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// READ VALUES
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int rv = dht_readSensor(pin, DHTLIB_DHT11_WAKEUP);
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if (rv != DHTLIB_OK)
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{
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dht_humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
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dht_temperature = DHTLIB_INVALID_VALUE; // invalid value
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return rv;
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}
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// CONVERT AND STORE
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dht_humidity = dht_bytes[0]; // dht_bytes[1] == 0;
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dht_temperature = dht_bytes[2]; // dht_bytes[3] == 0;
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// TEST CHECKSUM
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// dht_bytes[1] && dht_bytes[3] both 0
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uint8_t sum = dht_bytes[0] + dht_bytes[1] + dht_bytes[2] + dht_bytes[3];
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if (dht_bytes[4] != sum) return DHTLIB_ERROR_CHECKSUM;
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return DHTLIB_OK;
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}
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_CHECKSUM
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// DHTLIB_ERROR_TIMEOUT
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int dht_read(uint8_t pin)
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{
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// READ VALUES
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int rv = dht_readSensor(pin, DHTLIB_DHT_WAKEUP);
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if (rv != DHTLIB_OK)
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{
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dht_humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
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dht_temperature = DHTLIB_INVALID_VALUE; // invalid value
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return rv; // propagate error value
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}
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// CONVERT AND STORE
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dht_humidity = (double)COMBINE_HIGH_AND_LOW_BYTE(dht_bytes[0], dht_bytes[1]) * 0.1;
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dht_temperature = (double)COMBINE_HIGH_AND_LOW_BYTE(dht_bytes[2] & 0x7F, dht_bytes[3]) * 0.1;
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if (dht_bytes[2] & 0x80) // negative dht_temperature
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{
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dht_temperature = -dht_temperature;
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}
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// TEST CHECKSUM
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uint8_t sum = dht_bytes[0] + dht_bytes[1] + dht_bytes[2] + dht_bytes[3];
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if (dht_bytes[4] != sum)
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{
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return DHTLIB_ERROR_CHECKSUM;
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}
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return DHTLIB_OK;
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}
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_CHECKSUM
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// DHTLIB_ERROR_TIMEOUT
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int dht_read21(uint8_t pin) __attribute__((alias("dht_read")));
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_CHECKSUM
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// DHTLIB_ERROR_TIMEOUT
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int dht_read22(uint8_t pin) __attribute__((alias("dht_read")));
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_CHECKSUM
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// DHTLIB_ERROR_TIMEOUT
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int dht_read33(uint8_t pin) __attribute__((alias("dht_read")));
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_CHECKSUM
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// DHTLIB_ERROR_TIMEOUT
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int dht_read44(uint8_t pin) __attribute__((alias("dht_read")));
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/////////////////////////////////////////////////////
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//
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// PRIVATE
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//
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_TIMEOUT
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int dht_readSensor(uint8_t pin, uint8_t wakeupDelay)
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{
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// INIT BUFFERVAR TO RECEIVE DATA
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uint8_t mask = 128;
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uint8_t idx = 0;
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uint8_t i = 0;
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// replace digitalRead() with Direct Port Reads.
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// reduces footprint ~100 bytes => portability issue?
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// direct port read is about 3x faster
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// uint8_t bit = digitalPinToBitMask(pin);
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// uint8_t port = digitalPinToPort(pin);
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// volatile uint8_t *PIR = portInputRegister(port);
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// EMPTY BUFFER
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for (i = 0; i < 5; i++) dht_bytes[i] = 0;
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// REQUEST SAMPLE
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// pinMode(pin, OUTPUT);
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platform_gpio_mode(pin, PLATFORM_GPIO_OUTPUT, PLATFORM_GPIO_PULLUP);
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DIRECT_MODE_OUTPUT(pin);
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// digitalWrite(pin, LOW); // T-be
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DIRECT_WRITE_LOW(pin);
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// delay(wakeupDelay);
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for (i = 0; i < wakeupDelay; i++) os_delay_us(1000);
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// Disable interrupts
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ets_intr_lock();
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// digitalWrite(pin, HIGH); // T-go
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DIRECT_WRITE_HIGH(pin);
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os_delay_us(40);
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// pinMode(pin, INPUT);
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DIRECT_MODE_INPUT(pin);
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// GET ACKNOWLEDGE or TIMEOUT
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uint16_t loopCntLOW = DHTLIB_TIMEOUT;
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while (DIRECT_READ(pin) == LOW ) // T-rel
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{
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os_delay_us(1);
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if (--loopCntLOW == 0) return DHTLIB_ERROR_TIMEOUT;
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}
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uint16_t loopCntHIGH = DHTLIB_TIMEOUT;
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while (DIRECT_READ(pin) != LOW ) // T-reh
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{
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os_delay_us(1);
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if (--loopCntHIGH == 0) return DHTLIB_ERROR_TIMEOUT;
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}
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// READ THE OUTPUT - 40 BITS => 5 BYTES
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for (i = 40; i != 0; i--)
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{
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loopCntLOW = DHTLIB_TIMEOUT;
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while (DIRECT_READ(pin) == LOW )
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{
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os_delay_us(1);
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if (--loopCntLOW == 0) return DHTLIB_ERROR_TIMEOUT;
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}
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uint32_t t = system_get_time();
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loopCntHIGH = DHTLIB_TIMEOUT;
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while (DIRECT_READ(pin) != LOW )
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{
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os_delay_us(1);
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if (--loopCntHIGH == 0) return DHTLIB_ERROR_TIMEOUT;
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}
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if ((system_get_time() - t) > 40)
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{
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dht_bytes[idx] |= mask;
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}
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mask >>= 1;
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if (mask == 0) // next byte?
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{
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mask = 128;
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idx++;
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}
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}
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// Enable interrupts
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ets_intr_unlock();
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// pinMode(pin, OUTPUT);
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DIRECT_MODE_OUTPUT(pin);
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// digitalWrite(pin, HIGH);
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DIRECT_WRITE_HIGH(pin);
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return DHTLIB_OK;
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}
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//
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// END OF FILE
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//
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