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SI70XXTEMP(4)                Device Drivers Manual               SI70XXTEMP(4)

NAME
     si70xxtemp - Driver for Silicon Labs SI7013/SI7020/SI7021, HTU21D and
     SHT21 sensor chip via I2C bus

SYNOPSIS
     si70xxtemp* at iic? addr 0x40

DESCRIPTION
     The si70xxtemp driver provides measurements from the SI7013/SI7020/SI7021
     humidity/temperature sensors via the envsys(4) framework.  The si70xxtemp
     addr argument selects the address at the iic(4) bus.  The resolution,
     heater control and crc validity can be changed through sysctl(8) nodes.

SYSCTL VARIABLES
     The following sysctl(3) variables are provided:

     hw.si70xxtemp0.resolutions
             Lists the resolutions supported by the driver and chip.

     hw.si70xxtemp0.resolution
             Set the resolution, or number of bits, used for %RH and
             temperature.  Use one of the strings listed in
             hw.si70xxtemp.resolutions.

     hw.si70xxtemp0.ignorecrc
             If set, the crc calculation for %RH and temperature will be
             ignored.

     hw.si70xxtemp0.vddok
             If 1, the chip is getting enough power.

     hw.si70xxtemp0.heateron
             Turn the heater on and off.

     hw.si70xxtemp0.heaterstrength
             From 1 to 6, the amount of energy put into the heater.  The
             higher the number, the more power used.

             Some HTU21D chips do not support a heater register.  These chips
             are detected and the heater features of the driver will be
             disabled.

     hw.si70xxtemp0.debug
             If the driver is compiled with SI70XX_DEBUG, this node will
             appear and can be used to set the debugging level.

     hw.si70xxtemp0.readattempts
             To read %RH or temperature the driver uses a No Hold Master
             command.  This command needs to be sent to the device, a wait
             must then occur and then another read command is sent to read
             back the values.  Depending on the resolution, and other factors,
             the wait time varies.  The driver will attempt to read back the
             values readattempts number of times.  The default is 40 which
             should be enough for most purposes.  There is an initial wait of
             10,500 microseconds followed by a additional 1,000 microseconds
             per read attempt.

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

HISTORY
     The si70xxtemp driver first appeared in NetBSD 8.0.

AUTHORS
     The si70xxtemp driver was written by Brad Spencer
     <brad@anduin.eldar.org>.

NetBSD 10.99                   December 28, 2017                  NetBSD 10.99