192 lines
5.0 KiB
Groff
192 lines
5.0 KiB
Groff
.\"
|
|
.\" Copyright (c) 2014 Luiz Otavio O Souza <loos@freebsd.org>
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd May 11, 2014
|
|
.Dt LM75 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm lm75
|
|
.Nd lm75 i2c digital temperature sensor driver
|
|
.Sh SYNOPSIS
|
|
.Cd "device iic"
|
|
.Cd "device iicbus"
|
|
.Cd "device lm75"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
driver provides access to sensor data and configuration over the
|
|
.Xr iicbus 4 .
|
|
.Pp
|
|
It provides an easy and simple way to check the functionality of an i2c bus
|
|
as it provides read and write access to the
|
|
.Nm
|
|
configuration register.
|
|
.Pp
|
|
The access to
|
|
.Nm
|
|
data is made via the
|
|
.Xr sysctl 8
|
|
interface:
|
|
.Bd -literal
|
|
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
|
|
.Ed
|
|
.Bl -tag -width ".Va dev.lm75.%d.temperature"
|
|
.It Va dev.lm75.%d.temperature
|
|
Is the read-only value of the current temperature read by the sensor.
|
|
.It Va 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.
|
|
.It Va 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.
|
|
.It Va 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.
|
|
.It Va dev.lm75.%d.mode
|
|
Sets the operation mode for the sensor interrupt pin.
|
|
It can be set to 'comparator' (default) or 'interrupt'.
|
|
.It Va 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.
|
|
.It Va 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.
|
|
.El
|
|
.Pp
|
|
Please check the
|
|
.Nm
|
|
datasheet for more details.
|
|
.Pp
|
|
When used together with
|
|
.Xr snmp_lm75 3
|
|
it allows the monitoring of
|
|
.Nm
|
|
temperature data over SNMP.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
driver supports both the low and the high resolution models.
|
|
.Pp
|
|
The low resolution model (lm75) provides a 9 bit output with the LSB
|
|
representing 0.5C.
|
|
.Pp
|
|
The high resolution model (lm75a) provides an 11 bit output with the LSB
|
|
representing 0.125C.
|
|
.Pp
|
|
The driver tries to auto-detect the
|
|
.Nm
|
|
model, but the detection of some
|
|
.Nm
|
|
clones may not work reliably.
|
|
.Pp
|
|
On a
|
|
.Xr device.hints 5
|
|
based system, like
|
|
.Li MIPS ,
|
|
these values are configurable for
|
|
.Nm :
|
|
.Bl -tag -width ".Va hint.lm75.%d.addr"
|
|
.It Va hint.lm75.%d.at
|
|
Is the
|
|
.Xr iicbus 4
|
|
you are attaching to.
|
|
.It Va hint.lm75.%d.addr
|
|
Is the
|
|
.Nm
|
|
i2c address on the
|
|
.Xr iicbus 4 .
|
|
.El
|
|
.Pp
|
|
On a
|
|
.Xr FDT 4
|
|
based system, like
|
|
.Li ARM ,
|
|
the DTS part for a
|
|
.Nm
|
|
device usually looks like:
|
|
.Bd -literal
|
|
i2c {
|
|
|
|
...
|
|
|
|
lm750 {
|
|
compatible = "national,lm75";
|
|
i2c-address = <0x49>;
|
|
};
|
|
};
|
|
.Ed
|
|
.Pp
|
|
Where:
|
|
.Bl -tag -width ".Va i2c-address"
|
|
.It Va compatible
|
|
Should always be set to "national,lm75".
|
|
.It Va i2c-address
|
|
The
|
|
.Va i2c-address
|
|
property indicates which i2c address the
|
|
.Nm
|
|
is wired at.
|
|
.Nm
|
|
temperature sensors can be wired to 8 different addresses, allowing up to 8
|
|
sensors on the same
|
|
.Xr iicbus 4 .
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr snmp_lm75 3 ,
|
|
.Xr fdt 4 ,
|
|
.Xr iic 4 ,
|
|
.Xr iicbus 4 ,
|
|
.Xr sysctl 8
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
driver first appeared in
|
|
.Fx 11.0 .
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
The
|
|
.Nm
|
|
driver and this manual page were written by
|
|
.An Luiz Otavio O Souza Aq Mt loos@FreeBSD.org .
|