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Kernel driver lm73
==================
Supported chips:
* Texas Instruments LM73
Prefix: 'lm73'
Addresses scanned: I2C
0x48,
0x49,
0x4a,
0x4c,
0x4d, and
0x4e
Datasheet: Publicly available at the Texas Instruments website
https://www.ti.com/product/lm73
Author: Guillaume Ligneul <guillaume.ligneul@gmail.com>
Documentation: Chris Verges <kg4ysn@gmail.com>
Description
-----------
The LM73 is a digital temperature sensor. All temperature values are
given in degrees Celsius.
Measurement Resolution Support
------------------------------
The LM73 supports four resolutions, defined in terms of degrees C per
LSB:
0.
25,
0.
125,
0.
0625, and
0.
3125. Changing the resolution mode
affects the conversion time of the LM73's analog-to-digital converter.
From userspace, the desired resolution can be specified as a function of
conversion time via the 'update_interval' sysfs attribute for the
device. This attribute will normalize ranges of input values to the
maximum times defined for the resolution in the datasheet.
============= ============= ============
Resolution Conv. Time Input Range
(C/LSB) (msec) (msec)
============= ============= ============
0.
25 14 0..
14
0.
125 28 15..
28
0.
0625 56 29..
56
0.
03125 112 57..infinity
============= ============= ============
The following examples show how the 'update_interval' attribute can be
used to change the conversion time::
$ echo
0 > update_interval
$ cat update_interval
14
$ cat temp1_input
24250
$ echo
22 > update_interval
$ cat update_interval
28
$ cat temp1_input
24125
$ echo
56 > update_interval
$ cat update_interval
56
$ cat temp1_input
24062
$ echo
85 > update_interval
$ cat update_interval
112
$ cat temp1_input
24031
As shown here, the lm73 driver automatically adjusts any user input for
'update_interval' via a step function. Reading back the
'update_interval' value after a write operation will confirm the
conversion time actively in use.
Mathematically, the resolution can be derived from the conversion time
via the following function:
g(x) =
0.
250 * [log(x/
14) / log(
2)]
where 'x' is the output from 'update_interval' and 'g(x)' is the
resolution in degrees C per LSB.
Alarm Support
-------------
The LM73 features a simple over-temperature alarm mechanism. This
feature is exposed via the sysfs attributes.
The attributes 'temp1_max_alarm' and 'temp1_min_alarm' are flags
provided by the LM73 that indicate whether the measured temperature has
passed the 'temp1_max' and 'temp1_min' thresholds, respectively. These
values _must_ be read to clear the registers on the LM73.
