dht22.h File Reference

This Propeller C library was created for the DHT22 temperature and humidity sensor module. More...

Go to the source code of this file.

Macros
#define	__DHT22_SENSOR_H__
#define	CELSIUS   0
#define	FAHRENHEIT   1
#define	KELVIN   2

Functions
char	dht22_read (int dht_pin)
	Triggers a reading from the temperature and humidity from the sensor module. More...
void	dht22_set_timeout_ignore (int dht_pin, char ignore_timeout)
	The function is used to set or clear an ignore timeout instruction for modules connected to the specified pin. More...
int	dht22_getTemp (char temp_units)
	Retrieves the last temperature reading made by the read_dht22() function. More...
int	dht22_getHumidity ()
	Retrieves the last humidity reading made by the read_dht22() function. More...

Detailed Description

This Propeller C library was created for the DHT22 temperature and humidity sensor module.

This Propeller C library was created for the DHT22/CM2302 temperature and humidity sensor module.

Author

Matthew Matz

Version

0.5

Copyright

Copyright (C) Parallax, Inc. 2017. All Rights MIT Licensed.

Function Documentation

dht22_getHumidity()

int dht22_getHumidity

(

)

Retrieves the last humidity reading made by the read_dht22() function.

Returns

the last relative humidity read in tenths of a percent.

dht22_getTemp()

int dht22_getTemp

(

char

temp_units

)

Retrieves the last temperature reading made by the read_dht22() function.

Parameters

temp_units

allows the temperature unit to be specified in (0) Celsius, (1) Fahrenheit, or (2) Kelvin.

Returns

the temperature read in degree-tenths.

dht22_read()

char dht22_read

(

int

dht_pin

)

Triggers a reading from the temperature and humidity from the sensor module.

This function instructs the temperature and humidity sensor module to take a reading.

Note

The sensor can be read every 500ms. If this function is called before 500ms from the previous call has elapsed, the function waits unless the dht22_set_timeout_ignore() function was used to inttruct modules on that pin to ignore the 0.5 second minimum timeout.

Parameters

dht_pin

defines which pin the sensor is attached to. Requires a 10 kOhm pullup resistor to 3.3V when connecting to the Propeller MCU.

Returns

1 if a valid checksum was recieved, 0 if the checksum is invalid.

dht22_set_timeout_ignore()

void dht22_set_timeout_ignore	(	int	dht_pin,
		char	ignore_timeout
	)

The function is used to set or clear an ignore timeout instruction for modules connected to the specified pin.

Parameters

dht_pin	defines which pin the sensor is attached to.
ignore_timeout	when true (1), the function instructs the Propeller MCU to ignore the protective timeout that prevents the sensor from being read before it is ready. This parameter is set to false (0) by default.