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SHT3XTEMP(4) Device Drivers 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
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
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.
NetBSD 11.99 October 31, 2021 NetBSD 11.99