DHT Class
DHT Class
Description
A class to use DHT temperature and humidity sensors.
Syntax
class DHT
Members
| Public Constructors | |
| DHT::DHT | Constructs a DHT object. |
| Public Methods | |
| DHT::begin | Initialize the DHT sensor by setting up the sensor GPIO pin and set pull timings. |
| DHT::readTemperature | Read temperature(Fahrenheit or Celsius) from the DHT sensor. |
| DHT::convertCtoF | Convert a value from Celsius to Fahrenheit. |
| DHT::convertFtoC | Convert a temperature value from Fahrenheit to Celsius. |
| DHT::readHumidity | Read humidity value from the DHT sensor as percentage. |
| DHT::computeHeatIndex | Compute the HeatIndex from the readings (Using both Rothfusz and Steadman’s equations). |
| DHT::read | Check if the sensor is readable. |
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.
