1Kernel driver lm73
2==================
3
4Supported chips:
5
6  * Texas Instruments LM73
7
8    Prefix: 'lm73'
9
10    Addresses scanned: I2C 0x48, 0x49, 0x4a, 0x4c, 0x4d, and 0x4e
11
12    Datasheet: Publicly available at the Texas Instruments website
13
14	       https://www.ti.com/product/lm73
15
16
17Author: Guillaume Ligneul <guillaume.ligneul@gmail.com>
18
19Documentation: Chris Verges <kg4ysn@gmail.com>
20
21
22Description
23-----------
24
25The LM73 is a digital temperature sensor.  All temperature values are
26given in degrees Celsius.
27
28Measurement Resolution Support
29------------------------------
30
31The LM73 supports four resolutions, defined in terms of degrees C per
32LSB: 0.25, 0.125, 0.0625, and 0.3125.  Changing the resolution mode
33affects the conversion time of the LM73's analog-to-digital converter.
34From userspace, the desired resolution can be specified as a function of
35conversion time via the 'update_interval' sysfs attribute for the
36device.  This attribute will normalize ranges of input values to the
37maximum times defined for the resolution in the datasheet.
38
39    ============= ============= ============
40    Resolution    Conv. Time    Input Range
41    (C/LSB)       (msec)        (msec)
42    ============= ============= ============
43    0.25          14             0..14
44    0.125         28            15..28
45    0.0625        56            29..56
46    0.03125       112           57..infinity
47    ============= ============= ============
48
49The following examples show how the 'update_interval' attribute can be
50used to change the conversion time::
51
52    $ echo 0 > update_interval
53    $ cat update_interval
54    14
55    $ cat temp1_input
56    24250
57
58    $ echo 22 > update_interval
59    $ cat update_interval
60    28
61    $ cat temp1_input
62    24125
63
64    $ echo 56 > update_interval
65    $ cat update_interval
66    56
67    $ cat temp1_input
68    24062
69
70    $ echo 85 > update_interval
71    $ cat update_interval
72    112
73    $ cat temp1_input
74    24031
75
76As shown here, the lm73 driver automatically adjusts any user input for
77'update_interval' via a step function.  Reading back the
78'update_interval' value after a write operation will confirm the
79conversion time actively in use.
80
81Mathematically, the resolution can be derived from the conversion time
82via the following function:
83
84   g(x) = 0.250 * [log(x/14) / log(2)]
85
86where 'x' is the output from 'update_interval' and 'g(x)' is the
87resolution in degrees C per LSB.
88
89Alarm Support
90-------------
91
92The LM73 features a simple over-temperature alarm mechanism.  This
93feature is exposed via the sysfs attributes.
94
95The attributes 'temp1_max_alarm' and 'temp1_min_alarm' are flags
96provided by the LM73 that indicate whether the measured temperature has
97passed the 'temp1_max' and 'temp1_min' thresholds, respectively.  These
98values _must_ be read to clear the registers on the LM73.
99