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Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

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