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diff --git a/Documentation/hwmon/ntc_thermistor.rst b/Documentation/hwmon/ntc_thermistor.rst new file mode 100644 index 000000000..d0e7f9172 --- /dev/null +++ b/Documentation/hwmon/ntc_thermistor.rst @@ -0,0 +1,111 @@ +Kernel driver ntc_thermistor +============================ + +Supported thermistors from Murata: + +* Murata NTC Thermistors NCP15WB473, NCP18WB473, NCP21WB473, NCP03WB473, + NCP15WL333, NCP03WF104, NCP15XH103 + + Prefixes: 'ncp15wb473', 'ncp18wb473', 'ncp21wb473', 'ncp03wb473', + 'ncp15wl333', 'ncp03wf104', 'ncp15xh103' + + 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. + +Using the following convention:: + + $ resistor + [TH] the thermistor + +The four circuit models provided are: + +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 RO always 4 (thermistor) + +temp1_input RO measure the temperature and provide the measured value. + (reading this file initiates the reading procedure.) +=============== == ============================================================= + +Note that each NTC thermistor has only _one_ thermistor; thus, only temp1 exists. |