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/* Copyright 2018 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.
*/
/*
* Common thermistor code for Chrome EC. See ./thermistor.md for table of
* resistance of a 47kΩ B4050 thermistor
*/
#include "adc.h"
#include "common.h"
#include "gpio.h"
#include "temp_sensor/thermistor.h"
#include "util.h"
int thermistor_linear_interpolate(uint16_t mv,
const struct thermistor_info *info)
{
const struct thermistor_data_pair *data = info->data;
int v_high = 0, v_low = 0, t_low, t_high, num_steps;
int head, tail, mid = 0;
/* We need at least two points to form a line. */
ASSERT(info->num_pairs >= 2);
/*
* If input value is out of bounds return the lowest or highest
* value in the data sets provided.
*/
if (mv > data[0].mv * info->scaling_factor)
return data[0].temp;
else if (mv < data[info->num_pairs - 1].mv * info->scaling_factor)
return data[info->num_pairs - 1].temp;
head = 0;
tail = info->num_pairs - 1;
while (head != tail) {
mid = (head + tail) / 2;
v_high = data[mid].mv * info->scaling_factor;
v_low = data[mid + 1].mv * info->scaling_factor;
if ((mv <= v_high) && (mv >= v_low))
break;
else if (mv > v_high)
tail = mid;
else if (mv < v_low)
head = mid + 1;
}
t_low = data[mid].temp;
t_high = data[mid + 1].temp;
/*
* The obvious way of doing this is to figure out how many mV per
* degree are in between the two points (mv_per_deg_c), and then how
* many of those exist between the input voltage and voltage of
* lower temperature :
* 1. mv_per_deg_c = (v_high - v_low) / (t_high - t_low)
* 2. num_steps = (v_high - mv) / mv_per_deg_c
* 3. result = t_low + num_steps
*
* Combine #1 and #2 to mitigate precision loss due to integer division.
*/
num_steps = ((v_high - mv) * (t_high - t_low)) / (v_high - v_low);
return t_low + num_steps;
}
#if defined(CONFIG_STEINHART_HART_3V3_51K1_47K_4050B) || \
defined(CONFIG_STEINHART_HART_3V3_13K7_47K_4050B) || \
defined(CONFIG_STEINHART_HART_6V0_51K1_47K_4050B) || \
defined(CONFIG_STEINHART_HART_3V0_22K6_47K_4050B) || \
defined(CONFIG_STEINHART_HART_3V3_30K9_47K_4050B) || \
defined(CONFIG_ZEPHYR)
int thermistor_get_temperature(int idx_adc, int *temp_ptr,
const struct thermistor_info *info)
{
int mv;
#ifdef CONFIG_TEMP_SENSOR_POWER_GPIO
/*
* If the power rail for the thermistor circuit is not enabled, then
* need to ignore any ADC measurments.
*/
if (!gpio_get_level(CONFIG_TEMP_SENSOR_POWER_GPIO))
return EC_ERROR_NOT_POWERED;
#endif /* CONFIG_TEMP_SENSOR_POWER_GPIO */
mv = adc_read_channel(idx_adc);
if (mv < 0)
return EC_ERROR_UNKNOWN;
*temp_ptr = thermistor_linear_interpolate(mv, info);
*temp_ptr = C_TO_K(*temp_ptr);
return EC_SUCCESS;
}
#endif
#ifdef CONFIG_STEINHART_HART_3V3_51K1_47K_4050B
/*
* Data derived from Steinhart-Hart equation in a resistor divider circuit with
* Vdd=3300mV, R = 51.1Kohm, and thermistor (B = 4050, T0 = 298.15 K, nominal
* resistance (R0) = 47Kohm).
*/
#define THERMISTOR_SCALING_FACTOR_51_47 11
static const struct thermistor_data_pair thermistor_data_51_47[] = {
{ 2484 / THERMISTOR_SCALING_FACTOR_51_47, 0 },
{ 2142 / THERMISTOR_SCALING_FACTOR_51_47, 10 },
{ 1767 / THERMISTOR_SCALING_FACTOR_51_47, 20 },
{ 1400 / THERMISTOR_SCALING_FACTOR_51_47, 30 },
{ 1072 / THERMISTOR_SCALING_FACTOR_51_47, 40 },
{ 802 / THERMISTOR_SCALING_FACTOR_51_47, 50 },
{ 593 / THERMISTOR_SCALING_FACTOR_51_47, 60 },
{ 436 / THERMISTOR_SCALING_FACTOR_51_47, 70 },
{ 321 / THERMISTOR_SCALING_FACTOR_51_47, 80 },
{ 276 / THERMISTOR_SCALING_FACTOR_51_47, 85 },
{ 237 / THERMISTOR_SCALING_FACTOR_51_47, 90 },
{ 204 / THERMISTOR_SCALING_FACTOR_51_47, 95 },
{ 177 / THERMISTOR_SCALING_FACTOR_51_47, 100 },
};
static const struct thermistor_info thermistor_info_51_47 = {
.scaling_factor = THERMISTOR_SCALING_FACTOR_51_47,
.num_pairs = ARRAY_SIZE(thermistor_data_51_47),
.data = thermistor_data_51_47,
};
int get_temp_3v3_51k1_47k_4050b(int idx_adc, int *temp_ptr)
{
return thermistor_get_temperature(idx_adc, temp_ptr,
&thermistor_info_51_47);
}
#endif /* CONFIG_STEINHART_HART_3V3_51K1_47K_4050B */
#ifdef CONFIG_STEINHART_HART_3V3_13K7_47K_4050B
/*
* Data derived from Steinhart-Hart equation in a resistor divider circuit with
* Vdd=3300mV, R = 13.7Kohm, and thermistor (B = 4050, T0 = 298.15 K, nominal
* resistance (R0) = 47Kohm).
*/
#define THERMISTOR_SCALING_FACTOR_13_47 13
static const struct thermistor_data_pair thermistor_data_13_47[] = {
{ 3033 / THERMISTOR_SCALING_FACTOR_13_47, 0 },
{ 2882 / THERMISTOR_SCALING_FACTOR_13_47, 10 },
{ 2677 / THERMISTOR_SCALING_FACTOR_13_47, 20 },
{ 2420 / THERMISTOR_SCALING_FACTOR_13_47, 30 },
{ 2119 / THERMISTOR_SCALING_FACTOR_13_47, 40 },
{ 1799 / THERMISTOR_SCALING_FACTOR_13_47, 50 },
{ 1485 / THERMISTOR_SCALING_FACTOR_13_47, 60 },
{ 1197 / THERMISTOR_SCALING_FACTOR_13_47, 70 },
{ 947 / THERMISTOR_SCALING_FACTOR_13_47, 80 },
{ 839 / THERMISTOR_SCALING_FACTOR_13_47, 85 },
{ 741 / THERMISTOR_SCALING_FACTOR_13_47, 90 },
{ 653 / THERMISTOR_SCALING_FACTOR_13_47, 95 },
{ 576 / THERMISTOR_SCALING_FACTOR_13_47, 100 },
};
static const struct thermistor_info thermistor_info_13_47 = {
.scaling_factor = THERMISTOR_SCALING_FACTOR_13_47,
.num_pairs = ARRAY_SIZE(thermistor_data_13_47),
.data = thermistor_data_13_47,
};
int get_temp_3v3_13k7_47k_4050b(int idx_adc, int *temp_ptr)
{
return thermistor_get_temperature(idx_adc, temp_ptr,
&thermistor_info_13_47);
}
#endif /* CONFIG_STEINHART_HART_3V3_13K7_47K_4050B */
#ifdef CONFIG_STEINHART_HART_6V0_51K1_47K_4050B
/*
* Data derived from Steinhart-Hart equation in a resistor divider circuit with
* Vdd=6000mV, R = 51.1Kohm, and thermistor (B = 4050, T0 = 298.15 K, nominal
* resistance (R0) = 47Kohm).
*/
#define THERMISTOR_SCALING_FACTOR_6V0_51_47 18
static const struct thermistor_data_pair thermistor_data_6v0_51_47[] = {
{ 4517 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 0 },
{ 3895 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 10 },
{ 3214 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 20 },
{ 2546 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 30 },
{ 1950 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 40 },
{ 1459 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 50 },
{ 1079 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 60 },
{ 794 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 70 },
{ 584 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 80 },
{ 502 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 85 },
{ 432 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 90 },
{ 372 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 95 },
{ 322 / THERMISTOR_SCALING_FACTOR_6V0_51_47, 100 },
};
static const struct thermistor_info thermistor_info_6v0_51_47 = {
.scaling_factor = THERMISTOR_SCALING_FACTOR_6V0_51_47,
.num_pairs = ARRAY_SIZE(thermistor_data_6v0_51_47),
.data = thermistor_data_6v0_51_47,
};
int get_temp_6v0_51k1_47k_4050b(int idx_adc, int *temp_ptr)
{
return thermistor_get_temperature(idx_adc, temp_ptr,
&thermistor_info_6v0_51_47);
}
#endif /* CONFIG_STEINHART_HART_6V0_51K1_47K_4050B */
#ifdef CONFIG_STEINHART_HART_3V0_22K6_47K_4050B
/*
* Data derived from Steinhart-Hart equation in a resistor divider circuit with
* Vdd=3000mV, R = 22.6Kohm, and thermistor (B = 4050, T0 = 298.15 K, nominal
* resistance (R0) = 47Kohm).
*/
#define THERMISTOR_SCALING_FACTOR_22_47 11
static const struct thermistor_data_pair thermistor_data_22_47[] = {
{ 2619 / THERMISTOR_SCALING_FACTOR_22_47, 0 },
{ 2421 / THERMISTOR_SCALING_FACTOR_22_47, 10 },
{ 2168 / THERMISTOR_SCALING_FACTOR_22_47, 20 },
{ 1875 / THERMISTOR_SCALING_FACTOR_22_47, 30 },
{ 1563 / THERMISTOR_SCALING_FACTOR_22_47, 40 },
{ 1262 / THERMISTOR_SCALING_FACTOR_22_47, 50 },
{ 994 / THERMISTOR_SCALING_FACTOR_22_47, 60 },
{ 769 / THERMISTOR_SCALING_FACTOR_22_47, 70 },
{ 588 / THERMISTOR_SCALING_FACTOR_22_47, 80 },
{ 513 / THERMISTOR_SCALING_FACTOR_22_47, 85 },
{ 448 / THERMISTOR_SCALING_FACTOR_22_47, 90 },
{ 390 / THERMISTOR_SCALING_FACTOR_22_47, 95 },
{ 340 / THERMISTOR_SCALING_FACTOR_22_47, 100 },
};
static const struct thermistor_info thermistor_info_22_47 = {
.scaling_factor = THERMISTOR_SCALING_FACTOR_22_47,
.num_pairs = ARRAY_SIZE(thermistor_data_22_47),
.data = thermistor_data_22_47,
};
int get_temp_3v0_22k6_47k_4050b(int idx_adc, int *temp_ptr)
{
return thermistor_get_temperature(idx_adc, temp_ptr,
&thermistor_info_22_47);
}
#endif /* CONFIG_STEINHART_HART_3V0_22K6_47K_4050B */
#ifdef CONFIG_STEINHART_HART_3V3_30K9_47K_4050B
/*
* Data derived from Steinhart-Hart equation in a resistor divider circuit with
* Vdd=3300mV, R = 30.9Kohm, and thermistor (B = 4050, T0 = 298.15 K, nominal
* resistance (R0) = 47Kohm).
*/
#define THERMISTOR_SCALING_FACTOR_31_47 11
static const struct thermistor_data_pair thermistor_data_31_47[] = {
{ 2753 / THERMISTOR_SCALING_FACTOR_31_47, 0 },
{ 2487 / THERMISTOR_SCALING_FACTOR_31_47, 10 },
{ 2165 / THERMISTOR_SCALING_FACTOR_31_47, 20 },
{ 1813 / THERMISTOR_SCALING_FACTOR_31_47, 30 },
{ 1145 / THERMISTOR_SCALING_FACTOR_31_47, 50 },
{ 878 / THERMISTOR_SCALING_FACTOR_31_47, 60 },
{ 665 / THERMISTOR_SCALING_FACTOR_31_47, 70 },
{ 500 / THERMISTOR_SCALING_FACTOR_31_47, 80 },
{ 375 / THERMISTOR_SCALING_FACTOR_31_47, 90 },
{ 282 / THERMISTOR_SCALING_FACTOR_31_47, 100 },
};
static const struct thermistor_info thermistor_info_31_47 = {
.scaling_factor = THERMISTOR_SCALING_FACTOR_31_47,
.num_pairs = ARRAY_SIZE(thermistor_data_31_47),
.data = thermistor_data_31_47,
};
int get_temp_3v3_30k9_47k_4050b(int idx_adc, int *temp_ptr)
{
return thermistor_get_temperature(idx_adc, temp_ptr,
&thermistor_info_31_47);
}
#endif /* CONFIG_STEINHART_HART_3V3_30K9_47K_4050B */
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