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f22aaaa7 DK |
1 | Kernel driver ntc_thermistor |
2 | ================= | |
3 | ||
4 | Supported thermistors: | |
5 | * Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473, NCP15WL333 | |
6 | Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473', 'ncp15wl333' | |
7 | Datasheet: Publicly available at Murata | |
8 | ||
9 | Other NTC thermistors can be supported simply by adding compensation | |
10 | tables; e.g., NCP15WL333 support is added by the table ncpXXwl333. | |
11 | ||
12 | Authors: | |
13 | MyungJoo Ham <myungjoo.ham@samsung.com> | |
14 | ||
15 | Description | |
16 | ----------- | |
17 | ||
18 | The NTC thermistor is a simple thermistor that requires users to provide the | |
19 | resistance and lookup the corresponding compensation table to get the | |
20 | temperature input. | |
21 | ||
22 | The NTC driver provides lookup tables with a linear approximation function | |
23 | and four circuit models with an option not to use any of the four models. | |
24 | ||
25 | The 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 | ||
77 | When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm, | |
78 | pulldown_ohm, and connect should be provided. When none of the four models | |
79 | are suitable or the user can get the resistance directly, the user should | |
80 | provide read_ohm and _not_ provide the others. | |
81 | ||
82 | Sysfs Interface | |
83 | --------------- | |
84 | name the mandatory global attribute, the thermistor name. | |
85 | ||
86 | temp1_type always 4 (thermistor) | |
87 | RO | |
88 | ||
89 | temp1_input measure the temperature and provide the measured value. | |
90 | (reading this file initiates the reading procedure.) | |
91 | RO | |
92 | ||
93 | Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists. |