78 lines
2.1 KiB
C++
78 lines
2.1 KiB
C++
/**
|
|
* @author Matthew Kennedy, (c) 2019
|
|
*/
|
|
|
|
#include "pch.h"
|
|
|
|
#include "thermistor_func.h"
|
|
|
|
#include <math.h>
|
|
|
|
SensorResult ThermistorFunc::convert(float ohms) const {
|
|
// This resistance should have already been validated - only
|
|
// thing we can check is that it's non-negative
|
|
if (ohms <= 0) {
|
|
return UnexpectedCode::Low;
|
|
}
|
|
|
|
float lnR = logf(ohms);
|
|
|
|
float lnR3 = lnR * lnR * lnR;
|
|
|
|
float recip = m_a + m_b * lnR + m_c * lnR3;
|
|
|
|
float kelvin = 1 / recip;
|
|
|
|
float celsius = convertKelvinToCelcius(kelvin);
|
|
|
|
// bounds check result - please don't try to run rusEfi when colder than -50C
|
|
// high end limit is required as this could be an oil temp sensor on an
|
|
// air cooled engine
|
|
if (celsius < -50) {
|
|
return UnexpectedCode::Low;
|
|
}
|
|
|
|
if (celsius > 250) {
|
|
return UnexpectedCode::High;
|
|
}
|
|
|
|
return celsius;
|
|
}
|
|
|
|
void ThermistorFunc::configure(thermistor_conf_s &cfg) {
|
|
// https://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation
|
|
float l1 = logf(cfg.resistance_1);
|
|
float l2 = logf(cfg.resistance_2);
|
|
float l3 = logf(cfg.resistance_3);
|
|
|
|
float y1 = 1 / convertCelsiusToKelvin(cfg.tempC_1);
|
|
float y2 = 1 / convertCelsiusToKelvin(cfg.tempC_2);
|
|
float y3 = 1 / convertCelsiusToKelvin(cfg.tempC_3);
|
|
|
|
float u2 = (y2 - y1) / (l2 - l1);
|
|
float u3 = (y3 - y1) / (l3 - l1);
|
|
|
|
m_c = ((u3 - u2) / (l3 - l2)) / (l1 + l2 + l3);
|
|
m_b = u2 - m_c * (l1 * l1 + l1 * l2 + l2 * l2);
|
|
m_a = y1 - (m_b + l1 * l1 * m_c) * l1;
|
|
|
|
float resistance10percent = cfg.resistance_1 + 0.1 * (cfg.resistance_2 - cfg.resistance_1);
|
|
float tempAt10percentPoint = convert(resistance10percent).Value;
|
|
|
|
if (tempAt10percentPoint < cfg.tempC_1) {
|
|
#if EFI_UNIT_TEST
|
|
throw std::logic_error("Bad thermistor configuration at the left");
|
|
#endif
|
|
criticalError("Thermistor configuration has failed 10% test");
|
|
}
|
|
|
|
float resistance90percent = cfg.resistance_2 + 0.9 * (cfg.resistance_3 - cfg.resistance_2);
|
|
float tempAt90percentPoint = convert(resistance90percent).Value;
|
|
if (tempAt90percentPoint > cfg.tempC_3) {
|
|
#if EFI_UNIT_TEST
|
|
throw std::logic_error("Bad thermistor configuration at the right");
|
|
#endif
|
|
criticalError("Thermistor configuration has failed 90% test");
|
|
}
|
|
}
|