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Test different approach for resistance calculation

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This commit is contained in:
Leon Krieg
2024-09-19 21:34:24 +02:00
parent a548518b9c
commit 053ee1674d
1 changed files with 11 additions and 9 deletions
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20
src/common/math.c
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@@ -10,16 +10,19 @@
// TODO: Is resistance function semantically correct?
// TODO: Check results for humidity conversion functions.
// Thermistor general constants
#define R1 10000.0f // Resistor ohm value
#define VRES 0xFFFF // 16-bit ADC resolution
// Thermistor coeficients
static const float SC1 = 1.009249522e-3f;
static const float SC2 = 2.378405444e-4f;
static const float SC3 = 2.019202697e-7f;
static const float R1 = 10000.0f;
#define SC1 1.009249522e-3f
#define SC2 2.378405444e-4f
#define SC3 2.019202697e-7f
// Humidity conversion constants
static const float TH1 = 100.0f;
static const float TH2 = 243.04f;
static const float TH3 = 17.625f;
#define TH1 100.0f
#define TH2 243.04f
#define TH3 17.625f
float Resistance(int adc_raw)
{
@@ -30,10 +33,9 @@ float Resistance(int adc_raw)
// [GND] - [10K RESISTOR] - [ADC INPUT] - [THERMISTOR] - [VCC]
// return ((VRES - adc_raw) * R1) / adc_raw;
r2 = (float) adc_raw / 264.8f * 0.05f;
// XXX: Ohms Law solved for resistance?
// R = V / I
return R1 / (5.0f / r2 - 1.0f);
}