LM75(4) FreeBSD Kernel Interfaces Manual LM75(4)
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
<
[email protected]>.
FreeBSD 14.1-RELEASE-p8 December 26, 2017 FreeBSD 14.1-RELEASE-p8