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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. | ||