SHT3XTEMP(4)

NAME
sht3xtemp - Driver for Sensirion SHT30/SHT31/SHT35 sensor chip via I2C bus

SYNOPSIS
sht3xtemp* at iic? addr 0x44
sht3xtemp* at iic? addr 0x45

DESCRIPTION
The sht3xtemp driver provides measurements from the SHT30/SHT31/SHT35 humidity/temperature sensors via the envsys(4) framework. The sht3xtemp addr locator selects the address at the iic(4) bus. The mode of operation, repeatability, heater controls, periodic update rate and CRC validity can be changed through sysctl(8) nodes.

SYSCTL VARIABLES
The following sysctl(8) variables are provided:

hw.sht3xtemp0.modes
    Lists the modes supported by the driver and chip.

hw.sht3xtemp0.mode
    Set the operation mode of the chip. The SHT3X chip can run in a single-shot measurement mode or a periodic update mode. Use one of the strings listed in hw.sht3xtemp.modes.

hw.sht3xtemp0.rates
    List the periodic update rates supported by the driver and chip.

hw.sht3xtemp0.rate
    Set the periodic update rate when the mode of operation is set to periodic. The unit for this is measurements per second, or ART which is a mode that operates at an update rate of 4Hz higher response time. Use one of the strings listed in hw.sht3xtemp.rates.

    Since it is possible to have subsecond periodic updates from the chip if so desired a device file is provided that can be used to get the raw temperature and humidity values outside of the envsys(4) framework. The structure of this output is the raw temperature plus an 8-bit CRC followed by the raw humidity plus an 8-bit CRC.

hw.sht3xtemp0.repeatabilities
    List the valid values for the repeatability used for a measurement.

hw.sht3xtemp0.repeatability
    Set the repeatability for the measurement. The higher the repeatability the longer the measurement will take and the more power used. Use one of the strings listed in hw.sht3xtemp.repeatabilities.

hw.sht3xtemp0.ignorecrc
    If set, the crc calculation for %RH and temperature in the measurement phrase will be ignored.

hw.sht3xtemp0.heateron
    Turn the heater on and off.

hw.sht3xtemp0.debug
    If the driver is compiled with SHT3X_DEBUG, this node will appear and can be used to set the debugging level.

hw.sht3xtemp0.readattempts
    To read %RH or temperature the chip requires that the command be sent, then a delay must be observed before a read can be done to get the values back. The delays are documented in the datasheet for the chip. The driver will attempt to read back the values readattempts number of times. The default is 10 which should be more than enough for most purposes.

hw.sht3xtemp0.clockstretch
    The chip supports a set of commands that lets it use I2C clock stretching to perform the temperature or humidity measurement. If this is set to 1 then use the clock stretching commands with the device. Note that the I2C controller must support clock stretching in order for this to work reliability. When this option is enabled, the readattempts sysctl noted above will not be used. This option only apply to single shot measurements.

FILES
/dev/sht3xtempu
    SHT3X device unit u file.

SEE ALSO
envsys(4), iic(4), envstat(8), sysctl(8)

HISTORY
The sht3xtemp driver first appeared in NetBSD 10.0.

AUTHORS
-nosplit The sht3xtemp driver was written by Brad Spencer <brad@anduin.eldar.org>.

BUGS
The datasheet did not provide enough information to get the alarm function of the chip working.