sht3xtemp(4) - NetBSD Manual Pages

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SHT3XTEMP(4)            NetBSD Kernel Interfaces Manual           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 opera-
     tion, repeatability, heater controls, periodic update rate and CRC valid-
     ity 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 humid-
                       ity 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 readat-
                       tempts 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

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


BUGS

     The datasheet did not provide enough information to get the alarm func-
     tion of the chip working.

NetBSD 10.99                   October 31, 2021                   NetBSD 10.99