General Purpose Analog To Digital Converter (ADC) based thermal sensor.
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On some of platforms, thermal sensor like thermistors are connected to
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one of ADC channel and sensor resistance is read via voltage across the
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sensor resistor. The voltage read across the sensor is mapped to
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temperature using voltage-temperature lookup table.
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Required properties:
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===================
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- compatible: Must be "generic-adc-thermal".
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- temperature-lookup-table: Two dimensional array of Integer; lookup table
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to map the relation between ADC value and
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temperature. When ADC is read, the value is
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looked up on the table to get the equivalent
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temperature.
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The first value of the each row of array is the
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temperature in milliCelsius and second value of
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the each row of array is the ADC read value.
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- #thermal-sensor-cells: Should be 1. See ./thermal.txt for a description
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of this property.
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Example :
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#include <dt-bindings/thermal/thermal.h>
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i2c@7000c400 {
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ads1015: ads1015@4a {
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reg = <0x4a>;
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compatible = "ads1015";
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sampling-frequency = <3300>;
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#io-channel-cells = <1>;
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};
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};
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tboard_thermistor: thermal-sensor {
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compatible = "generic-adc-thermal";
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#thermal-sensor-cells = <0>;
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io-channels = <&ads1015 1>;
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io-channel-names = "sensor-channel";
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temperature-lookup-table = < (-40000) 2578
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(-39000) 2577
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(-38000) 2576
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(-37000) 2575
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(-36000) 2574
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(-35000) 2573
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(-34000) 2572
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(-33000) 2571
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(-32000) 2569
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(-31000) 2568
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(-30000) 2567
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::::::::::
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118000 254
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119000 247
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120000 240
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121000 233
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122000 226
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123000 220
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124000 214
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125000 208>;
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};
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dummy_cool_dev: dummy-cool-dev {
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compatible = "dummy-cooling-dev";
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#cooling-cells = <2>; /* min followed by max */
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};
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thermal-zones {
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Tboard {
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polling-delay = <15000>; /* milliseconds */
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polling-delay-passive = <0>; /* milliseconds */
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thermal-sensors = <&tboard_thermistor>;
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trips {
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therm_est_trip: therm_est_trip {
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temperature = <40000>;
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type = "active";
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hysteresis = <1000>;
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};
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};
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cooling-maps {
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map0 {
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trip = <&therm_est_trip>;
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cooling-device = <&dummy_cool_dev THERMAL_NO_LIMIT THERMAL_NO_LIMIT>;
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contribution = <100>;
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};
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};
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};
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};
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