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1 | Kernel driver ntc_thermistor |
2 | ================= | |
3 | ||
8b6f5e0f | 4 | Supported thermistors from Murata: |
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5 | * Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473, NCP15WL333 |
6 | Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473', 'ncp15wl333' | |
7 | Datasheet: Publicly available at Murata | |
8 | ||
ed67f087 JP |
9 | Supported thermistors from EPCOS: |
10 | * EPCOS NTC Thermistors B57330V2103 | |
11 | Prefixes: b57330v2103 | |
12 | Datasheet: Publicly available at EPCOS | |
13 | ||
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14 | Other NTC thermistors can be supported simply by adding compensation |
15 | tables; e.g., NCP15WL333 support is added by the table ncpXXwl333. | |
16 | ||
17 | Authors: | |
18 | MyungJoo Ham <myungjoo.ham@samsung.com> | |
19 | ||
20 | Description | |
21 | ----------- | |
22 | ||
8b6f5e0f NKC |
23 | The NTC (Negative Temperature Coefficient) thermistor is a simple thermistor |
24 | that requires users to provide the resistance and lookup the corresponding | |
25 | compensation table to get the temperature input. | |
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26 | |
27 | The NTC driver provides lookup tables with a linear approximation function | |
28 | and four circuit models with an option not to use any of the four models. | |
29 | ||
30 | The 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 | ||
82 | When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm, | |
83 | pulldown_ohm, and connect should be provided. When none of the four models | |
84 | are suitable or the user can get the resistance directly, the user should | |
85 | provide read_ohm and _not_ provide the others. | |
86 | ||
87 | Sysfs Interface | |
88 | --------------- | |
89 | name the mandatory global attribute, the thermistor name. | |
90 | ||
91 | temp1_type always 4 (thermistor) | |
92 | RO | |
93 | ||
94 | temp1_input measure the temperature and provide the measured value. | |
95 | (reading this file initiates the reading procedure.) | |
96 | RO | |
97 | ||
98 | Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists. |