SHT10/SHT11/SHT15 Humidity and Temperature Sensor

Driver for Sensirion SHT10/SHT11/SHT15 Humidity and Temperature Sensor. More...

Detailed Description

Driver for Sensirion SHT10/SHT11/SHT15 Humidity and Temperature Sensor.

Files
file	sht1x.h
	SHT10/SHT11/SHT15 Device Driver.
file	sht1x_defines.h
	Internal defines required by the SHT10/SHT11/SHT15 driver.
file	sht1x_params.h
	Default configuration for SHT10/SHT11/SHT15 devices.

Data Structures
struct	sht1x_dev_t
	SHT10/11/15 temperature humidity sensor. More...
struct	sht1x_params_t
	Parameters required to set up the SHT10/11/15 device driver. More...

Enumerations
enum	sht1x_conf_t { SHT1X_CONF_LOW_RESOLUTION = 0x01, SHT1X_CONF_SKIP_CALIBRATION = 0x02, SHT1X_CONF_ENABLE_HEATER = 0x04, SHT1X_CONF_SKIP_CRC = 0x08 }
	Possible configuration (=status byte) values of the SHT10/11/15. More...
enum	sht1x_vdd_t {   SHT1X_VDD_5_0V = 0, SHT1X_VDD_4_0V = 1, SHT1X_VDD_3_5V = 2, SHT1X_VDD_3_0V = 3,   SHT1X_VDD_2_5V = 4 }
	Possible values for Vdd (measured temperature depends on it)

Functions
int	sht1x_init (sht1x_dev_t *dev, const sht1x_params_t *params)
	Initialize the SHT10/11/15 sensor. More...
int16_t	sht1x_temperature (const sht1x_dev_t *dev, uint16_t raw)
	Calculate the temperature from the raw input. More...
int16_t	sht1x_humidity (const sht1x_dev_t *dev, uint16_t raw, int16_t temp)
	Calculate the relative humidity from the raw input. More...
int	sht1x_read (const sht1x_dev_t *dev, int16_t *temp, int16_t *hum)
	Read the current temperature. More...
int	sht1x_configure (sht1x_dev_t *dev, sht1x_conf_t conf)
	Apply the given configuration (= status byte) to. More...
int	sht1x_read_status (sht1x_dev_t *dev, uint8_t *status)
	Read the status byte of an SHT1X sensor. More...
int	sht1x_reset (sht1x_dev_t *dev)
	Reset the sensor's configuration to default values. More...

Enumeration Type Documentation

sht1x_conf_t

enum sht1x_conf_t

Possible configuration (=status byte) values of the SHT10/11/15.

These values can be or'ed together to get the configuration.

Enumerator
SHT1X_CONF_LOW_RESOLUTION	Use 8/12 bit resolution instead of 12/14 bit for temp/hum.
SHT1X_CONF_SKIP_CALIBRATION	Don't upload calibration data to register to safe 10 millisec.
SHT1X_CONF_ENABLE_HEATER	Waste 8mA at 5V to increase the sensor temperature up to 10°C.
SHT1X_CONF_SKIP_CRC	Skip the CRC check (and reading the CRC byte) to safe time.

Definition at line 38 of file sht1x.h.

Function Documentation

sht1x_configure()

int sht1x_configure	(	sht1x_dev_t *	dev,
		sht1x_conf_t	conf
	)

Apply the given configuration (= status byte) to.

Parameters

dev	SHT1X device to configure
conf	Configuration to apply

Return values

0	Configuration applied
-EINVAL	Called with dev == NULL
-EIO	I/O error (gpio_init() failed)
-EPROTO	Sensor did not acknowledge command
-ECANCELED	Sensor did not apply configuration
-EBADMSG	CRC checksum error while verifying uploaded configuration

sht1x_humidity()

int16_t sht1x_humidity	(	const sht1x_dev_t *	dev,
		uint16_t	raw,
		int16_t	temp
	)

Calculate the relative humidity from the raw input.

Note

This internal function is exposed for unit tests

Parameters

dev	Device from which the raw value was received
raw	The raw (unprocessed) temperature value
temp	The temperature at which the humidity was measure in E-02 °C

Returns

The correct temperature in E-02 %

Return values

-1	Passed NULL for parameter dev

sht1x_init()

int sht1x_init	(	sht1x_dev_t *	dev,
		const sht1x_params_t *	params
	)

Initialize the SHT10/11/15 sensor.

Parameters

dev	SHT1X sensor to initialize
params	Information on how the SHT1X is connected to the board

Return values

0	Success
-EIO	IO failure (gpio_init() failed)
-EPROTO	Sensor did not acknowledge reset command

sht1x_read()

int sht1x_read	(	const sht1x_dev_t *	dev,
		int16_t *	temp,
		int16_t *	hum
	)

Read the current temperature.

Parameters

dev	SHT1X sensor to read
temp	Store the measured temperature in E-02 °C here
hum	Store the measured relative humidity in E-02 % here

Return values

0	Success
-EIO	IO failure (gpio_init() failed)
-EBADMSG	CRC-8 checksum didn't match (--> Retry)
-EINVAL	Passed NULL for dev or for both temp and hum
-EBADMSG	CRC checksum didn't match
-ECANCELED	Measurement timed out
-EPROTO	Sensor did not acknowledge command

For either temp or hum NULL can be passed, if only one value is of interest. Passing NULL for hum speeds up the communication, but passing NULL for temp does not. The temperature value is required to calculate the relative humidity from the raw input. So the temperature is measured in any case, it is just not returned if temp is NULL.

sht1x_read_status()

int sht1x_read_status	(	sht1x_dev_t *	dev,
		uint8_t *	status
	)

Read the status byte of an SHT1X sensor.

Parameters

dev	SHT1X device to receive the status from
status	Store the received status byte here

Return values

0	Configuration applied
-EINVAL	Called with dev == NULL
-EIO	I/O error (gpio_init() failed)
-EPROTO	Sensor did not acknowledge command
-EBADMSG	CRC checksum didn't match

sht1x_reset()

int sht1x_reset

(

sht1x_dev_t *

dev

)

Reset the sensor's configuration to default values.

Parameters

dev	SHT1X device to reset

Return values

0	Reset successful
-EINVAL	Called with dev == NULL
-EIO	I/O error (gpio_init() failed)
-EPROTO	Sensor did not acknowledge reset command

sht1x_temperature()

int16_t sht1x_temperature	(	const sht1x_dev_t *	dev,
		uint16_t	raw
	)

Calculate the temperature from the raw input.

Note

This internal function is exposed for unit tests

Parameters

dev	Device from which the raw value was received
raw	The raw (unprocessed) temperature value

Returns

The correct temperature in E-02 °C

Return values

INT16_MIN

Passed NULL for parameter dev or dev->vdd