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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:
Donggeun Kimf22aaaa2011-06-20 16:48:19 +09005* Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473, NCP15WL333
6 Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473', 'ncp15wl333'
7 Datasheet: Publicly available at Murata
8
Johannes Pointnered67f082014-07-01 08:05:52 +02009Supported thermistors from EPCOS:
10* EPCOS NTC Thermistors B57330V2103
11 Prefixes: b57330v2103
12 Datasheet: Publicly available at EPCOS
13
Donggeun Kimf22aaaa2011-06-20 16:48:19 +090014Other NTC thermistors can be supported simply by adding compensation
15tables; e.g., NCP15WL333 support is added by the table ncpXXwl333.
16
17Authors:
18 MyungJoo Ham <myungjoo.ham@samsung.com>
19
20Description
21-----------
22
Naveen Krishna Chatradhi8b6f5e02014-06-25 11:59:31 +053023The NTC (Negative Temperature Coefficient) thermistor is a simple thermistor
24that requires users to provide the resistance and lookup the corresponding
25compensation table to get the temperature input.
Donggeun Kimf22aaaa2011-06-20 16:48:19 +090026
27The NTC driver provides lookup tables with a linear approximation function
28and four circuit models with an option not to use any of the four models.
29
30The four circuit models provided are:
31
32 $: resister, [TH]: the thermistor
33
34 1. connect = NTC_CONNECTED_POSITIVE, pullup_ohm > 0
35
36 [pullup_uV]
37 | |
38 [TH] $ (pullup_ohm)
39 | |
40 +----+-----------------------[read_uV]
41 |
42 $ (pulldown_ohm)
43 |
44 --- (ground)
45
46 2. connect = NTC_CONNECTED_POSITIVE, pullup_ohm = 0 (not-connected)
47
48 [pullup_uV]
49 |
50 [TH]
51 |
52 +----------------------------[read_uV]
53 |
54 $ (pulldown_ohm)
55 |
56 --- (ground)
57
58 3. connect = NTC_CONNECTED_GROUND, pulldown_ohm > 0
59
60 [pullup_uV]
61 |
62 $ (pullup_ohm)
63 |
64 +----+-----------------------[read_uV]
65 | |
66 [TH] $ (pulldown_ohm)
67 | |
68 -------- (ground)
69
70 4. connect = NTC_CONNECTED_GROUND, pulldown_ohm = 0 (not-connected)
71
72 [pullup_uV]
73 |
74 $ (pullup_ohm)
75 |
76 +----------------------------[read_uV]
77 |
78 [TH]
79 |
80 --- (ground)
81
82When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm,
83pulldown_ohm, and connect should be provided. When none of the four models
84are suitable or the user can get the resistance directly, the user should
85provide read_ohm and _not_ provide the others.
86
87Sysfs Interface
88---------------
89name the mandatory global attribute, the thermistor name.
90
91temp1_type always 4 (thermistor)
92 RO
93
94temp1_input measure the temperature and provide the measured value.
95 (reading this file initiates the reading procedure.)
96 RO
97
98Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists.