| Kernel driver ntc_thermistor | |
| ================= | |
| Supported thermistors: | |
| * Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473, NCP15WL333 | |
| Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473', 'ncp15wl333' | |
| Datasheet: Publicly available at Murata | |
| Other NTC thermistors can be supported simply by adding compensation | |
| tables; e.g., NCP15WL333 support is added by the table ncpXXwl333. | |
| Authors: | |
| MyungJoo Ham <myungjoo.ham@samsung.com> | |
| Description | |
| ----------- | |
| The NTC thermistor is a simple thermistor that requires users to provide the | |
| resistance and lookup the corresponding compensation table to get the | |
| temperature input. | |
| The NTC driver provides lookup tables with a linear approximation function | |
| and four circuit models with an option not to use any of the four models. | |
| The four circuit models provided are: | |
| $: resister, [TH]: the thermistor | |
| 1. connect = NTC_CONNECTED_POSITIVE, pullup_ohm > 0 | |
| [pullup_uV] | |
| | | | |
| [TH] $ (pullup_ohm) | |
| | | | |
| +----+-----------------------[read_uV] | |
| | | |
| $ (pulldown_ohm) | |
| | | |
| --- (ground) | |
| 2. connect = NTC_CONNECTED_POSITIVE, pullup_ohm = 0 (not-connected) | |
| [pullup_uV] | |
| | | |
| [TH] | |
| | | |
| +----------------------------[read_uV] | |
| | | |
| $ (pulldown_ohm) | |
| | | |
| --- (ground) | |
| 3. connect = NTC_CONNECTED_GROUND, pulldown_ohm > 0 | |
| [pullup_uV] | |
| | | |
| $ (pullup_ohm) | |
| | | |
| +----+-----------------------[read_uV] | |
| | | | |
| [TH] $ (pulldown_ohm) | |
| | | | |
| -------- (ground) | |
| 4. connect = NTC_CONNECTED_GROUND, pulldown_ohm = 0 (not-connected) | |
| [pullup_uV] | |
| | | |
| $ (pullup_ohm) | |
| | | |
| +----------------------------[read_uV] | |
| | | |
| [TH] | |
| | | |
| --- (ground) | |
| When one of the four circuit models is used, read_uV, pullup_uV, pullup_ohm, | |
| pulldown_ohm, and connect should be provided. When none of the four models | |
| are suitable or the user can get the resistance directly, the user should | |
| provide read_ohm and _not_ provide the others. | |
| Sysfs Interface | |
| --------------- | |
| name the mandatory global attribute, the thermistor name. | |
| temp1_type always 4 (thermistor) | |
| RO | |
| temp1_input measure the temperature and provide the measured value. | |
| (reading this file initiates the reading procedure.) | |
| RO | |
| Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists. |