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/* Copyright 2015 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
/* Thermistor module for Chrome EC */
#ifndef __CROS_EC_TEMP_SENSOR_THERMISTOR_H
#define __CROS_EC_TEMP_SENSOR_THERMISTOR_H
struct thermistor_data_pair {
uint8_t mv; /* Scaled voltage level at ADC (in mV) */
uint8_t temp; /* Temperature in Celsius */
};
struct thermistor_info {
uint8_t scaling_factor; /* Scaling factor for voltage in data pair. */
uint8_t num_pairs; /* Number of data pairs. */
/*
* Values between given data pairs will be calculated as points on
* a line. Pairs can be derived using the Steinhart-Hart equation.
*
* Guidelines for data sets:
* - Must contain at least two pairs.
* - First and last pairs are the max and min.
* - Pairs must be sorted in descending order.
* - 5 pairs should provide reasonable accuracy in most cases. Use
* points where the slope changes significantly or to recalibrate
* the algorithm if needed.
*/
const struct thermistor_data_pair *data;
};
/**
* Calculate temperature using linear interpolation of data points.
*
* Given a set of datapoints, the algorithm will calculate the "step" in
* between each one in order to interpolate missing entries.
*
* @param mv Value read from ADC (in millivolts).
* @param info Reference data set and info.
*
* @return temperature in C
*/
int thermistor_linear_interpolate(uint16_t mv,
const struct thermistor_info *info);
#ifdef CONFIG_THERMISTOR_NCP15WB
/**
* ncp15wb temperature conversion routine.
*
* @param adc 10bit raw data on adc.
*
* @return temperature in C.
*/
int ncp15wb_calculate_temp(uint16_t adc);
#endif /* CONFIG_THERMISTOR_NCP15WB */
#ifdef CONFIG_STEINHART_HART_3V3_13K7_47K_4050B
/**
* Reads the specified ADC channel and uses a lookup table and interpolation to
* return a temperature in degrees K.
*
* The lookup table is based off of a resistor divider circuit on 3.3V with a
* 13.7K resistor in series with a thermistor with nominal value of 47K (at 25C)
* and a B (25/100) value of 4050.
*
* @param idx_adc The idx value from the temp_sensor_t struct, which is
* the ADC channel to read and convert to degrees K
* @param temp_ptr Destination for temperature (in degrees K)
*
* @return EC_SUCCESS, or non-zero if error.
*/
int get_temp_3v3_13k7_47k_4050b(int idx_adc, int *temp_ptr);
#endif
#ifdef CONFIG_STEINHART_HART_3V3_51K1_47K_4050B
/**
* Reads the specified ADC channel and uses a lookup table and interpolation to
* return a temperature in degrees K.
*
* The lookup table is based off of a resistor divider circuit on 3.3V with a
* 51.1K resistor in series with a thermistor with nominal value of 47K (at 25C)
* and a B (25/100) value of 4050.
*
* @param idx_adc The idx value from the temp_sensor_t struct, which is
* the ADC channel to read and convert to degrees K
* @param temp_ptr Destination for temperature (in degrees K)
*
* @return EC_SUCCESS, or non-zero if error.
*/
int get_temp_3v3_51k1_47k_4050b(int idx_adc, int *temp_ptr);
#endif
#endif /* __CROS_EC_TEMP_SENSOR_THERMISTOR_NCP15WB_H */
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