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Diffstat (limited to 'kernel/Documentation/hwmon/ntc_thermistor')
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diff --git a/kernel/Documentation/hwmon/ntc_thermistor b/kernel/Documentation/hwmon/ntc_thermistor new file mode 100644 index 000000000..c5e05e290 --- /dev/null +++ b/kernel/Documentation/hwmon/ntc_thermistor @@ -0,0 +1,98 @@ +Kernel driver ntc_thermistor +================= + +Supported thermistors from Murata: +* Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473, NCP15WL333 + Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473', 'ncp15wl333' + Datasheet: Publicly available at Murata + +Supported thermistors from EPCOS: +* EPCOS NTC Thermistors B57330V2103 + Prefixes: b57330v2103 + Datasheet: Publicly available at EPCOS + +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 (Negative Temperature Coefficient) 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. |