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SI70XXTEMP(4) Device Drivers Manual SI70XXTEMP(4) NAME si70xxtemp - Driver for Silicon Labs SI7013/SI7020/SI7021 and HTU21D 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. 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 25 which should be more than 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 <email@example.com>. NetBSD 8.99.34 December 28, 2017 NetBSD 8.99.34