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authorDonggeun Kim <dg77.kim@samsung.com>2011-06-20 16:48:19 +0900
committerGuenter Roeck <guenter.roeck@ericsson.com>2011-07-28 00:17:33 -0700
commitf22aaaa70d8c24e5dc7d23a219c4beace8354b65 (patch)
tree855158946f04f4d4846b7cab573d55652163ec18 /Documentation/hwmon/ntc_thermistor
parentdabaa0d2b4085a2037d80a40b86ba215f00b601e (diff)
downloadkernel-f22aaaa70d8c24e5dc7d23a219c4beace8354b65.tar.gz
hwmon: Driver for NTC Thermistors
Add support for NTC Thermistor series. In this release, the following thermistors are supported: NCP15WB473, NCP18WB473, NCP03WB473, and NCP15WL333. This driver is based on the datasheet of MURATA. The driver in the patch does conversion from the raw ADC value (either voltage or resistence) to temperature. In order to use voltage values as input, the circuit schematics should be provided with the platform data. A compensation table for each type of thermistor is provided for the conversion. Signed-off-by: Donggeun Kim <dg77.kim@samsung.com> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Signed-off-by: KyungMin Park <kyungmin.park@samsung.com> Reviewed-by: Shubhrajyoti D <shubhrajyoti@ti.com> Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
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+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.