27 lines
793 B
C
27 lines
793 B
C
#include <math.h>
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#define NTC_A1 0.003354016f // see NTC RT csv from Vishay
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#define NTC_B1 0.000300131f
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#define NTC_C1 5.08516E-06f
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#define NTC_D1 2.18765E-07f
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#define NTC_R25 10000.0f // 10k ohm at 25C
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#define NTC_R_DIVIDER 10000.0f
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#define NTC_V_DIVIDER 3.000f // 3V
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[[gnu::always_inline]]
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static inline float ntc_ohms_to_celsius(float ohms) {
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float log_ohms = logf(ohms / NTC_R25);
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return 1.0f / (NTC_A1 + NTC_B1 * log_ohms + NTC_C1 * log_ohms * log_ohms + NTC_D1 * log_ohms * log_ohms * log_ohms) - 273.15f;
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}
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[[gnu::always_inline]]
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static inline float ohms_from_ntc_v(float v) {
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return (NTC_R_DIVIDER * v) / (NTC_V_DIVIDER - v);
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}
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[[maybe_unused]]
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static int ntc_mv_to_celsius(int mv) {
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float v = (float)mv * 0.001f;
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return (int)ntc_ohms_to_celsius(ohms_from_ntc_v(v));
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} |