kernel-ark/Documentation/hwmon/ntc_thermistor
Donggeun Kim f22aaaa70d 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>
2011-07-28 00:17:33 -07:00

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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.