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Commit | Line | Data |
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1 | Kernel driver ntc_thermistor | |
2 | ================= | |
3 | ||
4 | Supported thermistors from Murata: | |
5 | * Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473, | |
6 | NCP15WL333, NCP03WF104, NCP15XH103 | |
7 | Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473', | |
8 | 'ncp15wl333', 'ncp03wf104', 'ncp15xh103' | |
9 | Datasheet: Publicly available at Murata | |
10 | ||
11 | Supported thermistors from EPCOS: | |
12 | * EPCOS NTC Thermistors B57330V2103 | |
13 | Prefixes: b57330v2103 | |
14 | Datasheet: Publicly available at EPCOS | |
15 | ||
16 | Other NTC thermistors can be supported simply by adding compensation | |
17 | tables; e.g., NCP15WL333 support is added by the table ncpXXwl333. | |
18 | ||
19 | Authors: | |
20 | MyungJoo Ham <myungjoo.ham@samsung.com> | |
21 | ||
22 | Description | |
23 | ----------- | |
24 | ||
25 | The NTC (Negative Temperature Coefficient) thermistor is a simple thermistor | |
26 | that requires users to provide the resistance and lookup the corresponding | |
27 | compensation table to get the temperature input. | |
28 | ||
29 | The NTC driver provides lookup tables with a linear approximation function | |
30 | and four circuit models with an option not to use any of the four models. | |
31 | ||
32 | The 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 | ||
84 | When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm, | |
85 | pulldown_ohm, and connect should be provided. When none of the four models | |
86 | are suitable or the user can get the resistance directly, the user should | |
87 | provide read_ohm and _not_ provide the others. | |
88 | ||
89 | Sysfs Interface | |
90 | --------------- | |
91 | name the mandatory global attribute, the thermistor name. | |
92 | ||
93 | temp1_type always 4 (thermistor) | |
94 | RO | |
95 | ||
96 | temp1_input measure the temperature and provide the measured value. | |
97 | (reading this file initiates the reading procedure.) | |
98 | RO | |
99 | ||
100 | Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists. |