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NAME

     lm75 — lm75 i2c digital temperature sensor driver

SYNOPSIS

     device iic
     device iicbus
     device lm75

DESCRIPTION

     The lm75 driver provides access to sensor data and configuration over the iicbus(4).

     It provides an easy and simple way to check the functionality of an i2c bus as it provides read and write
     access to the lm75 configuration register.

     The access to lm75 data is made via the sysctl(8) interface:

     dev.lm75.0.%desc: LM75 temperature sensor
     dev.lm75.0.%driver: lm75
     dev.lm75.0.%location: addr=0x49
     dev.lm75.0.%pnpinfo: name=lm750 compat=national,lm75
     dev.lm75.0.%parent: iicbus3
     dev.lm75.0.temperature: 27.1C
     dev.lm75.0.thyst: 75.0C
     dev.lm75.0.tos: 80.0C
     dev.lm75.0.faults: 1
     dev.lm75.0.mode: comparator
     dev.lm75.0.polarity: active-low
     dev.lm75.0.shutdown: 0

     dev.lm75.%d.temperature  Is the read-only value of the current temperature read by the sensor.

     dev.lm75.%d.thyst        Sets the hysteresis temperature.  Once the temperature gets over the
                              overtemperature shutdown value (tos) it needs to drop below the hysteresis
                              temperature to disable the output (interrupt) pin again.

     dev.lm75.%d.tos          Sets the overtemperature shutdown value.  Once the temperature gets over this
                              value the output pin will be enabled.  The way the output (interrupt) pin works,
                              depends on the mode configuration.

     dev.lm75.%d.faults       Is the number of faults that must occur consecutively to activate the interrupt
                              (output) pin.  It can be set to 1, 2, 4, and 6.

     dev.lm75.%d.mode         Sets the operation mode for the sensor interrupt pin.  It can be set to
                              'comparator' (default) or 'interrupt'.

     dev.lm75.%d.polarity     Sets the polarity of the sensor interrupt pin.  It can be set to 'active-low'
                              (default) or 'active-high'.  Please note that the output pin is an open-drain
                              output and it needs a proper pull-up resistor to work.

     dev.lm75.%d.shutdown     When set to '1' it shuts down the sensor.  The temperature conversion stops but
                              the sensor remains with its i2c bus active, i.e., it can be woken up by setting
                              this option to '0' again.

     Please check the lm75 datasheet for more details.

     When used together with snmp_lm75(3) it allows the monitoring of lm75 temperature data over SNMP.

     The lm75 driver supports both the low and the high resolution models.

     The low resolution model (lm75) provides a 9 bit output with the LSB representing 0.5C.

     The high resolution model (lm75a) provides an 11 bit output with the LSB representing 0.125C.

     The driver tries to auto-detect the lm75 model, but the detection of some lm75 clones may not work
     reliably.

     On a device.hints(5) based system, such as MIPS, these values are configurable for lm75:

     hint.lm75.%d.at    Is the iicbus(4) you are attaching to.

     hint.lm75.%d.addr  Is the lm75 i2c address on the iicbus(4).

     On a FDT(4) based system, such as ARM, the DTS part for a lm75 device usually looks like:

     i2c {
             /* Properties describing the controller appear here. */
             ...
             lm750@49 {
                     compatible = "national,lm75";
                     reg = <0x49>;
             };
     };

     Where:

     compatible  Should always be set to "national,lm75".

     reg         Indicates which 7-bit i2c address the lm75 is wired at.  lm75 temperature sensors can be wired
                 to 8 different addresses, allowing up to 8 sensors on the same iicbus(4).

SEE ALSO

     snmp_lm75(3), fdt(4), iic(4), iicbus(4), sysctl(8)

HISTORY

     The lm75 driver first appeared in FreeBSD 11.0.

AUTHORS

     The lm75 driver and this manual page were written by Luiz Otavio O Souza <loos@FreeBSD.org>.