1.\" $NetBSD: si70xxtemp.4,v 1.7 2021/11/12 15:12:11 brad Exp $ 2.\" 3.\" Copyright (c) 2017 Brad Spencer <brad@anduin.eldar.org> 4.\" 5.\" Permission to use, copy, modify, and distribute this software for any 6.\" purpose with or without fee is hereby granted, provided that the above 7.\" copyright notice and this permission notice appear in all copies. 8.\" 9.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16.\" 17.Dd December 28, 2017 18.Dt SI70XXTEMP 4 19.Os 20.Sh NAME 21.Nm si70xxtemp 22.Nd Driver for Silicon Labs SI7013/SI7020/SI7021, HTU21D and SHT21 sensor chip via I2C bus 23.Sh SYNOPSIS 24.Cd "si70xxtemp* at iic? addr 0x40" 25.Sh DESCRIPTION 26The 27.Nm 28driver provides measurements from the SI7013/SI7020/SI7021 humidity/temperature 29sensors via the 30.Xr envsys 4 31framework. 32The 33.Nm 34.Ar addr 35argument selects the address at the 36.Xr iic 4 37bus. 38The resolution, heater control and crc validity can be changed through 39.Xr sysctl 8 40nodes. 41.Sh SYSCTL VARIABLES 42The following 43.Xr sysctl 3 44variables are provided: 45.Bl -tag -width indent 46.It hw.si70xxtemp0.resolutions 47Lists the resolutions supported by the driver and chip. 48.It hw.si70xxtemp0.resolution 49Set the resolution, or number of bits, used for %RH and temperature. 50Use one of the strings listed in hw.si70xxtemp.resolutions. 51.It hw.si70xxtemp0.ignorecrc 52If set, the crc calculation for %RH and temperature will be ignored. 53.It hw.si70xxtemp0.vddok 54If 1, the chip is getting enough power. 55.It hw.si70xxtemp0.heateron 56Turn the heater on and off. 57.It hw.si70xxtemp0.heaterstrength 58From 1 to 6, the amount of energy put into the heater. 59The higher the number, the more power used. 60.Pp 61Some HTU21D chips do not support a heater register. 62These chips are detected and the heater features of the driver will 63be disabled. 64.It hw.si70xxtemp0.debug 65If the driver is compiled with 66.Dv SI70XX_DEBUG , 67this node will appear and can be used to set the debugging level. 68.It hw.si70xxtemp0.readattempts 69To read %RH or temperature the driver uses a No Hold Master command. 70This command needs to be sent to the device, a wait must then occur 71and then another read command is sent to read back the values. 72Depending on the resolution, and other factors, the wait time varies. 73The driver will attempt to read back the values readattempts number of 74times. 75The default is 40 which should be enough for most purposes. 76There is an initial wait of 10,500 microseconds followed by 77a additional 1,000 microseconds per read attempt. 78.El 79.Sh SEE ALSO 80.Xr envsys 4 , 81.Xr iic 4 , 82.Xr envstat 8 , 83.Xr sysctl 8 84.Sh HISTORY 85The 86.Nm 87driver first appeared in 88.Nx 8.0 . 89.Sh AUTHORS 90.An -nosplit 91The 92.Nm 93driver was written by 94.An Brad Spencer Aq Mt brad@anduin.eldar.org . 95