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1 | /** | |||
2 | * @author Matthew Kennedy, (c) 2019 | |||
3 | */ | |||
4 | ||||
5 | #include "pch.h" | |||
6 | ||||
7 | #include "thermistor_func.h" | |||
8 | ||||
9 | #include <cmath> | |||
10 | ||||
11 | 31 | SensorResult ThermistorFunc::convert(float ohms) const { | ||
12 | // This resistance should have already been validated - only | |||
13 | // thing we can check is that it's non-negative | |||
14 |
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31 | if (ohms <= 0) { |
15 | ✗ | return UnexpectedCode::Low; | ||
16 | } | |||
17 | ||||
18 | 31 | float lnR = logf(ohms); | ||
19 | ||||
20 | 31 | float lnR3 = lnR * lnR * lnR; | ||
21 | ||||
22 | 31 | float recip = m_a + m_b * lnR + m_c * lnR3; | ||
23 | ||||
24 | 31 | float kelvin = 1 / recip; | ||
25 | ||||
26 | 31 | float celsius = convertKelvinToCelcius(kelvin); | ||
27 | ||||
28 | // bounds check result - please don't try to run rusEfi when colder than -50C | |||
29 | // high end limit is required as this could be an oil temp sensor on an | |||
30 | // air cooled engine | |||
31 |
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31 | if (celsius < -50) { |
32 | ✗ | return UnexpectedCode::Low; | ||
33 | } | |||
34 | ||||
35 |
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31 | if (celsius > 250) { |
36 | ✗ | return UnexpectedCode::High; | ||
37 | } | |||
38 | ||||
39 | 31 | return celsius; | ||
40 | } | |||
41 | ||||
42 | 7 | void ThermistorFunc::configure(thermistor_conf_s &cfg) { | ||
43 | // https://en.wikipedia.org/wiki/Steinhart%E2%80%93Hart_equation | |||
44 | 7 | float l1 = logf(cfg.resistance_1); | ||
45 | 7 | float l2 = logf(cfg.resistance_2); | ||
46 | 7 | float l3 = logf(cfg.resistance_3); | ||
47 | ||||
48 | 7 | float y1 = 1 / convertCelsiusToKelvin(cfg.tempC_1); | ||
49 | 7 | float y2 = 1 / convertCelsiusToKelvin(cfg.tempC_2); | ||
50 | 7 | float y3 = 1 / convertCelsiusToKelvin(cfg.tempC_3); | ||
51 | ||||
52 | 7 | float u2 = (y2 - y1) / (l2 - l1); | ||
53 | 7 | float u3 = (y3 - y1) / (l3 - l1); | ||
54 | ||||
55 | 7 | m_c = ((u3 - u2) / (l3 - l2)) / (l1 + l2 + l3); | ||
56 | 7 | m_b = u2 - m_c * (l1 * l1 + l1 * l2 + l2 * l2); | ||
57 | 7 | m_a = y1 - (m_b + l1 * l1 * m_c) * l1; | ||
58 | ||||
59 | 7 | float resistance10percent = cfg.resistance_1 + 0.1 * (cfg.resistance_2 - cfg.resistance_1); | ||
60 | 7 | float tempAt10percentPoint = convert(resistance10percent).Value; | ||
61 | ||||
62 |
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7 | if (tempAt10percentPoint < cfg.tempC_1) { |
63 | #if EFI_UNIT_TEST | |||
64 | ✗ | throw std::logic_error("Bad thermistor configuration at the left"); | ||
65 | #endif | |||
66 | criticalError("Thermistor configuration has failed 10% test"); | |||
67 | } | |||
68 | ||||
69 | 7 | float resistance90percent = cfg.resistance_2 + 0.9 * (cfg.resistance_3 - cfg.resistance_2); | ||
70 | 7 | float tempAt90percentPoint = convert(resistance90percent).Value; | ||
71 |
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7 | if (tempAt90percentPoint > cfg.tempC_3) { |
72 | #if EFI_UNIT_TEST | |||
73 |
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1 | throw std::logic_error("Bad thermistor configuration at the right"); | |
74 | #endif | |||
75 | criticalError("Thermistor configuration has failed 90% test"); | |||
76 | } | |||
77 | 6 | } | ||
78 |