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Donggeun Kimf22aaaa2011-06-20 16:48:19 +09001Kernel driver ntc_thermistor
2=================
3
Naveen Krishna Chatradhi8b6f5e02014-06-25 11:59:31 +05304Supported thermistors from Murata:
Beomho Seo887ee432015-04-30 13:07:43 +09005* Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473,
6 NCP15WL333, NCP03WF104
7 Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473',
8 'ncp15wl333', 'ncp03wf104'
Donggeun Kimf22aaaa2011-06-20 16:48:19 +09009 Datasheet: Publicly available at Murata
10
Johannes Pointnered67f082014-07-01 08:05:52 +020011Supported thermistors from EPCOS:
12* EPCOS NTC Thermistors B57330V2103
13 Prefixes: b57330v2103
14 Datasheet: Publicly available at EPCOS
15
Donggeun Kimf22aaaa2011-06-20 16:48:19 +090016Other NTC thermistors can be supported simply by adding compensation
17tables; e.g., NCP15WL333 support is added by the table ncpXXwl333.
18
19Authors:
20 MyungJoo Ham <myungjoo.ham@samsung.com>
21
22Description
23-----------
24
Naveen Krishna Chatradhi8b6f5e02014-06-25 11:59:31 +053025The NTC (Negative Temperature Coefficient) thermistor is a simple thermistor
26that requires users to provide the resistance and lookup the corresponding
27compensation table to get the temperature input.
Donggeun Kimf22aaaa2011-06-20 16:48:19 +090028
29The NTC driver provides lookup tables with a linear approximation function
30and four circuit models with an option not to use any of the four models.
31
32The four circuit models provided are:
33
34 $: resister, [TH]: the thermistor
35
36 1. connect = NTC_CONNECTED_POSITIVE, pullup_ohm > 0
37
38 [pullup_uV]
39 | |
40 [TH] $ (pullup_ohm)
41 | |
42 +----+-----------------------[read_uV]
43 |
44 $ (pulldown_ohm)
45 |
46 --- (ground)
47
48 2. connect = NTC_CONNECTED_POSITIVE, pullup_ohm = 0 (not-connected)
49
50 [pullup_uV]
51 |
52 [TH]
53 |
54 +----------------------------[read_uV]
55 |
56 $ (pulldown_ohm)
57 |
58 --- (ground)
59
60 3. connect = NTC_CONNECTED_GROUND, pulldown_ohm > 0
61
62 [pullup_uV]
63 |
64 $ (pullup_ohm)
65 |
66 +----+-----------------------[read_uV]
67 | |
68 [TH] $ (pulldown_ohm)
69 | |
70 -------- (ground)
71
72 4. connect = NTC_CONNECTED_GROUND, pulldown_ohm = 0 (not-connected)
73
74 [pullup_uV]
75 |
76 $ (pullup_ohm)
77 |
78 +----------------------------[read_uV]
79 |
80 [TH]
81 |
82 --- (ground)
83
84When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm,
85pulldown_ohm, and connect should be provided. When none of the four models
86are suitable or the user can get the resistance directly, the user should
87provide read_ohm and _not_ provide the others.
88
89Sysfs Interface
90---------------
91name the mandatory global attribute, the thermistor name.
92
93temp1_type always 4 (thermistor)
94 RO
95
96temp1_input measure the temperature and provide the measured value.
97 (reading this file initiates the reading procedure.)
98 RO
99
100Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists.