SHT3XTEMP(4) FreeBSD 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 argument 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(3) 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.
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 <
[email protected]>.
BUGS
The datasheet did not provide enough information to get the alarm
function of the chip working.
FreeBSD 14.1-RELEASE-p8 October 31, 2021 FreeBSD 14.1-RELEASE-p8