DHT Class

Description
A class to use DHT temperature and humidity sensors.

Syntax
class DHT

Members

DHT::DHT

Description
Constructs a DHT object.

Syntax
DHT(uint8_t pin, uint8_t type, uint8_t count);

Parameters
pin: selected GPIO pin on Ameba board. (Default: 8)
type: The DHT sensor type. Available sensor types: DHT11, DHT22 (AM2302, AM2321), or DHT21(AM2301). (Default: DHT11)
count: The count is now ignored as the DHT reading algorithm adjusts itself based on the speed of the processor. (Default: 6, see function declaration in DHT.h)

Returns
NA

Example Code
Example:DHTTester
(https://github.com/ambiot/ambd_arduino/blob/dev/Arduino_package/hardware/libraries/GPIO/examples/DHT_Tester/DHT_Tester.ino)

Notes and Warnings
“DHT.h” must be included to use the class function.

DHT::begin

Description
Initialize the DHT sensor by setting up the sensor GPIO pin and set pull timings.

Syntax
void begin(uint8_t usec);

Parameters
usec: Optionally pass pull-up time (in microseconds) before DHT reading starts. (Default: 55, see function declaration in DHT.h)

Returns
NA

Example Code
Example: DHTTester
(https://github.com/ambiot/ambd_arduino/blob/dev/Arduino_package/hardware/libraries/GPIO/examples/DHT_Tester/DHT_Tester.ino)

Notes and Warnings
“DHT.h” must be included to use the class function.

DHT::readTemperature

Description
Read temperature (Fahrenheit or Celsius) from the DHT sensor in selected scale.

Syntax
float readTemperature(bool S, bool force);

Parameters
S: Scale for temperature, available values: True (Fahrenheit) and False (Celsius). (Default: False, see function declaration in DHT.h)
force: Enable or disable force mode, available values: True (Force mode) and False (Disable force mode). (Default: False, see function declaration in DHT.h)

Returns
This function returns the current temperature as a float value in selected scale.

Example Code
Example: DHTTester
(https://github.com/ambiot/ambd_arduino/blob/dev/Arduino_package/hardware/libraries/GPIO/examples/DHT_Tester/DHT_Tester.ino)

Notes and Warnings
“DHT.h” must be included to use the class function.

DHT::convertCtoF

Description
Convert a temperature value from Celsius to Fahrenheit.

Syntax
float convertCtoF(float c);

Parameters
c: Temperature in Celsius.

Returns
This function returns the temperature in Fahrenheit as a float number.

Example Code
Example: DHTTester
(https://github.com/ambiot/ambd_arduino/blob/dev/Arduino_package/hardware/libraries/GPIO/examples/DHT_Tester/DHT_Tester.ino)

Notes and Warnings
“DHT.h” must be included to use the class function.

DHT::convertFtoC

Description
Convert a temperature value from Fahrenheit to Celsius.

Syntax
float convertFtoC(float f);

Parameters
f: Temperature in Fahrenheit

Returns
This function returns the temperature in Celsius as a float number.

Example Code
Example: DHTTester
(https://github.com/ambiot/ambd_arduino/blob/dev/Arduino_package/hardware/libraries/GPIO/examples/DHT_Tester/DHT_Tester.ino)

Notes and Warnings
“DHT.h” must be included to use the class function.

DHT::readHumidity

Description
Read humidity value from the DHT sensor as percentage.

Syntax
float readHumidity(bool force);

Parameters
force: force read mode. (Default: False, see function declaration in DHT.h)

Returns
This function returns current humidity value represented in float as percentage.

Example Code
Example: DHTTester
(https://github.com/ambiot/ambd_arduino/blob/dev/Arduino_package/hardware/libraries/GPIO/examples/DHT_Tester/DHT_Tester.ino)

Notes and Warnings
“DHT.h” must be included to use the class function. Reading temperature or humidity takes about 250 milliseconds! Sensor readings may also be up to 2 seconds.

DHT::computeHeatIndex

Description
Compute the HeatIndex from the readings (Using both Rothfusz and Steadman’s equations). More details refer to http://www.wpc.ncep.noaa.gov/html/heatindex_equation.shtml .

Syntax
float computeHeatIndex(bool isFahrenheit);
float computeHeatIndex(float temperature, float percentHumidity, bool isFahrenheit = true);

Parameters
temperature: The temperature value in selscted scale.
percentHumidity: humidity value in percentage.
isFahrenheit: choose temperature vale in Farenheit or Celsius. Available values: True (in Fahrenheit) or False (Celsius). (Default: True)

Returns
This function returns the heat index in Fahrenheit or Celsius as a float value.

Example Code
Example: DHTTester
(https://github.com/ambiot/ambd_arduino/blob/dev/Arduino_package/hardware/libraries/GPIO/examples/DHT_Tester/DHT_Tester.ino)

Notes and Warnings
“DHT.h” must be included to use the class function.

DHT::read

Description
Check if the sensor is readable.

Syntax
bool read (bool force);

Parameters
force: Enable or disable force mode. Available values: True (Force mode) and False (Disable force mode). (Default: False, see function declaration in DHT.h)

Returns
This function returns whether the sensor is readable in every two seconds.

Example Code
Example: DHTTester
(https://github.com/ambiot/ambd_arduino/blob/dev/Arduino_package/hardware/libraries/GPIO/examples/DHT_Tester/DHT_Tester.ino)

Notes and Warnings
“DHT.h” must be included to use the class function.