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