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Donggeun Kimf22aaaa2011-06-20 16:48:19 +09001Kernel driver ntc_thermistor
2=================
3
4Supported thermistors:
5* Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473, NCP15WL333
6 Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473', 'ncp15wl333'
7 Datasheet: Publicly available at Murata
8
9Other NTC thermistors can be supported simply by adding compensation
10tables; e.g., NCP15WL333 support is added by the table ncpXXwl333.
11
12Authors:
13 MyungJoo Ham <myungjoo.ham@samsung.com>
14
15Description
16-----------
17
18The NTC thermistor is a simple thermistor that requires users to provide the
19resistance and lookup the corresponding compensation table to get the
20temperature input.
21
22The NTC driver provides lookup tables with a linear approximation function
23and four circuit models with an option not to use any of the four models.
24
25The four circuit models provided are:
26
27 $: resister, [TH]: the thermistor
28
29 1. connect = NTC_CONNECTED_POSITIVE, pullup_ohm > 0
30
31 [pullup_uV]
32 | |
33 [TH] $ (pullup_ohm)
34 | |
35 +----+-----------------------[read_uV]
36 |
37 $ (pulldown_ohm)
38 |
39 --- (ground)
40
41 2. connect = NTC_CONNECTED_POSITIVE, pullup_ohm = 0 (not-connected)
42
43 [pullup_uV]
44 |
45 [TH]
46 |
47 +----------------------------[read_uV]
48 |
49 $ (pulldown_ohm)
50 |
51 --- (ground)
52
53 3. connect = NTC_CONNECTED_GROUND, pulldown_ohm > 0
54
55 [pullup_uV]
56 |
57 $ (pullup_ohm)
58 |
59 +----+-----------------------[read_uV]
60 | |
61 [TH] $ (pulldown_ohm)
62 | |
63 -------- (ground)
64
65 4. connect = NTC_CONNECTED_GROUND, pulldown_ohm = 0 (not-connected)
66
67 [pullup_uV]
68 |
69 $ (pullup_ohm)
70 |
71 +----------------------------[read_uV]
72 |
73 [TH]
74 |
75 --- (ground)
76
77When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm,
78pulldown_ohm, and connect should be provided. When none of the four models
79are suitable or the user can get the resistance directly, the user should
80provide read_ohm and _not_ provide the others.
81
82Sysfs Interface
83---------------
84name the mandatory global attribute, the thermistor name.
85
86temp1_type always 4 (thermistor)
87 RO
88
89temp1_input measure the temperature and provide the measured value.
90 (reading this file initiates the reading procedure.)
91 RO
92
93Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists.