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<table class="head">
<tr>
<td class="head-ltitle">LM75(4)</td>
<td class="head-vol">Device Drivers Manual</td>
<td class="head-rtitle">LM75(4)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">lm75</code> — <span class="Nd">lm75 i2c
digital temperature sensor driver</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="Cd">device iic</code>
<br/>
<code class="Cd">device iicbus</code>
<br/>
<code class="Cd">device lm75</code></p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The <code class="Nm">lm75</code> driver provides access to sensor
data and configuration over the <a class="Xr">iicbus(4)</a>.</p>
<p class="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
<code class="Nm">lm75</code> configuration register.</p>
<p class="Pp">The access to <code class="Nm">lm75</code> data is made via the
<a class="Xr">sysctl(8)</a> interface:</p>
<div class="Bd Pp Li">
<pre>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</pre>
</div>
<dl class="Bl-tag">
<dt id="dev.lm75._d.temperature"><var class="Va">dev.lm75.%d.temperature</var></dt>
<dd>Is the read-only value of the current temperature read by the sensor.</dd>
<dt id="dev.lm75._d.thyst"><var class="Va">dev.lm75.%d.thyst</var></dt>
<dd>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.</dd>
<dt id="dev.lm75._d.tos"><var class="Va">dev.lm75.%d.tos</var></dt>
<dd>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.</dd>
<dt id="dev.lm75._d.faults"><var class="Va">dev.lm75.%d.faults</var></dt>
<dd>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.</dd>
<dt id="dev.lm75._d.mode"><var class="Va">dev.lm75.%d.mode</var></dt>
<dd>Sets the operation mode for the sensor interrupt pin. It can be set to
'comparator' (default) or 'interrupt'.</dd>
<dt id="dev.lm75._d.polarity"><var class="Va">dev.lm75.%d.polarity</var></dt>
<dd>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.</dd>
<dt id="dev.lm75._d.shutdown"><var class="Va">dev.lm75.%d.shutdown</var></dt>
<dd>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.</dd>
</dl>
<p class="Pp">Please check the <code class="Nm">lm75</code> datasheet for more
details.</p>
<p class="Pp">When used together with <a class="Xr">snmp_lm75(3)</a> it allows
the monitoring of <code class="Nm">lm75</code> temperature data over
SNMP.</p>
<p class="Pp">The <code class="Nm">lm75</code> driver supports both the low and
the high resolution models.</p>
<p class="Pp">The low resolution model (lm75) provides a 9 bit output with the
LSB representing 0.5C.</p>
<p class="Pp">The high resolution model (lm75a) provides an 11 bit output with
the LSB representing 0.125C.</p>
<p class="Pp">The driver tries to auto-detect the <code class="Nm">lm75</code>
model, but the detection of some <code class="Nm">lm75</code> clones may not
work reliably.</p>
<p class="Pp">On a <a class="Xr">device.hints(5)</a> based system, such as
<code class="Li">MIPS</code>, these values are configurable for
<code class="Nm">lm75</code>:</p>
<dl class="Bl-tag">
<dt id="hint.lm75._d.at"><var class="Va">hint.lm75.%d.at</var></dt>
<dd>Is the <a class="Xr">iicbus(4)</a> you are attaching to.</dd>
<dt id="hint.lm75._d.addr"><var class="Va">hint.lm75.%d.addr</var></dt>
<dd>Is the <code class="Nm">lm75</code> i2c address on the
<a class="Xr">iicbus(4)</a>.</dd>
</dl>
<p class="Pp">On a <a class="Xr">FDT(4)</a> based system, such as
<code class="Li">ARM</code>, the DTS part for a <code class="Nm">lm75</code>
device usually looks like:</p>
<div class="Bd Pp Li">
<pre>i2c {
/* Properties describing the controller appear here. */
...
lm750@49 {
compatible = "national,lm75";
reg = <0x49>;
};
};</pre>
</div>
<p class="Pp">Where:</p>
<dl class="Bl-tag">
<dt id="compatible"><var class="Va">compatible</var></dt>
<dd>Should always be set to "national,lm75".</dd>
<dt id="reg"><var class="Va">reg</var></dt>
<dd>Indicates which 7-bit i2c address the <code class="Nm">lm75</code> is
wired at. <code class="Nm">lm75</code> temperature sensors can be wired to
8 different addresses, allowing up to 8 sensors on the same
<a class="Xr">iicbus(4)</a>.</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">snmp_lm75(3)</a>, <a class="Xr">fdt(4)</a>,
<a class="Xr">iic(4)</a>, <a class="Xr">iicbus(4)</a>,
<a class="Xr">sysctl(8)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Nm">lm75</code> driver first appeared in
<span class="Ux">FreeBSD 11.0</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<p class="Pp">The <code class="Nm">lm75</code> driver and this manual page were
written by <span class="An">Luiz Otavio O Souza</span>
<<a class="Mt" href="mailto:loos@FreeBSD.org">loos@FreeBSD.org</a>>.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">December 26, 2017</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
