SHT4XTEMP(4)

SHT4XTEMP(4) | Device Drivers Manual | SHT4XTEMP(4)

# NAME

`sht4xtemp` —
Driver for Sensirion SHT40/SHT41/SHT45 sensor chip via I2C bus

# SYNOPSIS

`sht4xtemp* at iic? addr 0x44`

# DESCRIPTION

The `sht4xtemp` driver provides measurements from the SHT40/SHT41/SHT45 humidity/temperature sensors via the envsys(4) framework. The `sht4xtemp` addr argument selects the address at the iic(4) bus. The resolution, heater controls and crc validity can be changed through sysctl(8) nodes.

# SYSCTL VARIABLES

The following sysctl(3) variables are provided:

`hw.sht4xtemp0.resolutions`
  Lists the resolutions supported by the driver and chip.
`hw.sht4xtemp0.resolution`
  Set the resolution, or number of bits, used for %RH and temperature. Use one of the strings listed in `hw.sht4xtemp.resolutions`.
`hw.sht4xtemp0.ignorecrc`
  If set, the crc calculation for %RH and temperature will be ignored.
`hw.sht4xtemp0.heateron`
  Turn the heater on and off. Please note that the heater is turned on right before the measurement and runs for a pulse width of time. Then the measurement is taken and the heater is turned off. There is no way to keep the heater running with this chip.
`hw.sht4xtemp0.heaterstrength`
  From 1 to 3, the amount of energy put into the heater. The higher the number, the more power used.
`hw.sht4xtemp0.heaterpulses`
  Lists the valid heater pulses supported by the driver and chip.
`hw.sht4xtemp0.heaterpulse`
  Set the heater pulse length. Use one of the strings listed in `hw.sht4xtemp.heaterpulses`.
`hw.sht4xtemp0.debug`
  If the driver is compiled with `SI70XX_DEBUG`, this node will appear and can be used to set the debugging level.
`hw.sht4xtemp0.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.

# SEE ALSO

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

# HISTORY

The `sht4xtemp` driver first appeared in NetBSD 10.0.

# AUTHORS

The `sht4xtemp` driver was written by Brad Spencer <brad@anduin.eldar.org>.

September 28, 2021 | NetBSD 10.0