diff options
| author | Vijay Hiremath <vijay.p.hiremath@intel.com> | 2019-04-02 21:58:22 -0700 |
|---|---|---|
| committer | chrome-bot <chrome-bot@chromium.org> | 2019-04-26 00:17:33 -0700 |
| commit | 2362b119299e2122832656aa0a1affda74654ce6 (patch) | |
| tree | 286725ba65299777114b03bf076fb4d04017c542 /driver/temp_sensor/thermistor.c | |
| parent | 5c931074f53de0bcac655d60e5867b3eb0959864 (diff) | |
| download | chrome-ec-2362b119299e2122832656aa0a1affda74654ce6.tar.gz | |
thermistor: Add STEINHART-HART lookup table for NCP15WB473F03RC
The lookup table is based off of a resistor divider circuit on 3.0V with
a 22.6K resistor in series with a thermistor with nominal value of 47K
(at 25C) and a B (25/100) value of 4050.
Calculation:
1. Get the thermistor resistance for a given temperature from the
datasheet.
2. Calculate the ADC input voltage.
Vout = (Vdd * Rt) / (Rt + Rs)
Where:
Vdd - Source voltage (Constant)
Vout - ADC value read on STEINHART-HART voltage divider circuit
Rt - Resistance of thermistor at given temperature
Rs - Series resistance value (constant)
3. Form a STEINHART-HART lookup table for 0 to 100 deg C
4. Add a scaling factor so that the STEINHART-HART lookup table data
is 1-byte per pair.
BUG=b:131060744
BRANCH=none
TEST=Manually tested on ICLRVP, able to read correct temperature
Change-Id: Ib0e7b1ab6d6d4c5bcb14ff4ab0e830881e9864e6
Signed-off-by: Vijay Hiremath <vijay.p.hiremath@intel.com>
Reviewed-on: https://chromium-review.googlesource.com/1577741
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Vijay P Hiremath <vijay.p.hiremath@intel.com>
Reviewed-by: Jett Rink <jettrink@chromium.org>
Diffstat (limited to 'driver/temp_sensor/thermistor.c')
| -rw-r--r-- | driver/temp_sensor/thermistor.c | 39 |
1 files changed, 38 insertions, 1 deletions
diff --git a/driver/temp_sensor/thermistor.c b/driver/temp_sensor/thermistor.c index 15295a00ea..25ff819321 100644 --- a/driver/temp_sensor/thermistor.c +++ b/driver/temp_sensor/thermistor.c @@ -65,7 +65,8 @@ int thermistor_linear_interpolate(uint16_t mv, #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_6V0_51K1_47K_4050B) || \ + defined(CONFIG_STEINHART_HART_3V0_22K6_47K_4050B) static int thermistor_get_temperature(int idx_adc, int *temp_ptr, const struct thermistor_info *info) { @@ -196,3 +197,39 @@ int get_temp_6v0_51k1_47k_4050b(int idx_adc, int *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[] = { + { 2625 / THERMISTOR_SCALING_FACTOR_22_47, 0 }, + { 2425 / THERMISTOR_SCALING_FACTOR_22_47, 10 }, + { 2170 / THERMISTOR_SCALING_FACTOR_22_47, 20 }, + { 1875 / THERMISTOR_SCALING_FACTOR_22_47, 30 }, + { 1563 / THERMISTOR_SCALING_FACTOR_22_47, 40 }, + { 1263 / THERMISTOR_SCALING_FACTOR_22_47, 50 }, + { 995 / THERMISTOR_SCALING_FACTOR_22_47, 60 }, + { 770 / THERMISTOR_SCALING_FACTOR_22_47, 70 }, + { 589 / THERMISTOR_SCALING_FACTOR_22_47, 80 }, + { 514 / THERMISTOR_SCALING_FACTOR_22_47, 85 }, + { 448 / THERMISTOR_SCALING_FACTOR_22_47, 90 }, + { 391 / THERMISTOR_SCALING_FACTOR_22_47, 95 }, + { 341 / 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 */ |