DHT Family of Humidity and Temperature Sensors

Device driver for the DHT Family of humidity and temperature sensors. More...

Detailed Description

Device driver for the DHT Family of humidity and temperature sensors.

This driver provides [S]ensor [A]ctuator [U]ber [L]ayer capabilities.

Files
file	dht_params.h
	Default configuration for DHT devices.
file	dht.h
	Device driver interface for the DHT family of humidity and temperature sensors.

Data Structures
struct	dht_data_t
	Data type for storing DHT sensor readings. More...
struct	dht_params_t
	Configuration parameters for DHT devices. More...
struct	dht_t
	Device descriptor for DHT sensor devices. More...

Enumerations
enum	{ DHT_OK = 0 , DHT_NOCSUM = -EIO , DHT_TIMEOUT = -ETIMEDOUT }
	Possible return codes. More...
enum	dht_type_t {   DHT11 , DHT11_2022 , DHT22 , DHT21 = DHT22 ,   AM2301 = DHT22 }
	Device type of the DHT device. More...

Functions
int	dht_init (dht_t *dev, const dht_params_t *params)
	Initialize a new DHT device.
int	dht_read (dht_t *dev, int16_t *temp, int16_t *hum)
	get a new temperature and/or humidity value from the device

Enumeration Type Documentation

anonymous enum

anonymous enum

Possible return codes.

Deprecated:

The functions use errno codes instead now

Enumerator
DHT_OK	all good
DHT_NOCSUM	checksum error
DHT_TIMEOUT	communication timed out

Definition at line 48 of file dht.h.

dht_type_t

enum dht_type_t

Device type of the DHT device.

Enumerator
DHT11	Older DHT11 variants with either 1 °C or 0.1 °C resolution.
DHT11_2022	New DHT11 variant with 0.01 °C resolution.
DHT22	DHT22 device identifier.
DHT21	DHT21 device identifier.
AM2301	AM2301 device identifier.

Definition at line 65 of file dht.h.

Function Documentation

dht_init()

int dht_init	(	dht_t *	dev,
		const dht_params_t *	params
	)

Initialize a new DHT device.

Parameters

[out]	dev	device descriptor of a DHT device
[in]	params	configuration parameters

Return values

0	Success
-EXDEV	A low level on the input after the sensor's startup time indicates that either no sensor or pull-up resistor is connected, or the sensor is physically poorly connected or powered.
-ENODEV	The sensor did not respond to the transmission of a start signal. Likely there were a pull-up resistor but no sensor connected on the data line.

dht_read()

int dht_read	(	dht_t *	dev,
		int16_t *	temp,
		int16_t *	hum
	)

get a new temperature and/or humidity value from the device

Note

if reading fails or checksum is invalid, no new values will be written into the result values

Parameters

[in]	dev	device descriptor of a DHT device
[out]	temp	temperature value [in °C * 10^-1], may be NULL if not needed
[out]	hum	relative humidity value [in percent * 10^-1], may be NULL if not needed

Return values

0	Success
-ENODEV	The sensor did not respond to the transmission of a start signal. Likely the RESPAWN_TIMEOUT is insufficient.
-EIO	The received and the expected checksum didn't match.
-ENOSYS	Unable to parse the received data. Likely the data format is not implemented.
-ERANGE	Temperature low byte >= 10. Likely misconfigured device type (DHT11_2022).