| Donggeun Kim | f22aaaa | 2011-06-20 16:48:19 +0900 | [diff] [blame] | 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. |