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/*
* Thermistor.h
*
* Created on: 10 Nov 2016
* Author: David
*/
#ifndef SRC_HEATING_THERMISTOR_H_
#define SRC_HEATING_THERMISTOR_H_
#include "TemperatureSensor.h"
// The Steinhart-Hart equation for thermistor resistance is:
// 1/T = A + B ln(R) + C [ln(R)]^3
//
// The simplified (beta) equation assumes C=0 and is:
// 1/T = A + (1/Beta) ln(R)
//
// The parameters that can be configured in RRF are R25 (the resistance at 25C), Beta, and optionally C.
class Thermistor : public TemperatureSensor
{
public:
Thermistor(unsigned int channel); // create an instance with default values
bool Configure(unsigned int mCode, unsigned int heater, GCodeBuffer& gb, StringRef& reply, bool& error) override; // configure the sensor from M305 parameters
void Init() override;
TemperatureError GetTemperature(float& t) override;
private:
float CalcTemperature(int32_t adcReading) const; // calculate temperature from an ADC reading in the range 0..1
int32_t CalcAdcReading(float temperature) const; // calculate expected ADC reading at a particular temperature
float GetR25() const { return r25; }
float GetBeta() const { return beta; }
float GetShc() const { return shC; }
float GetSeriesR() const { return seriesR; }
int8_t GetLowOffset() const { return adcLowOffset; }
int8_t GetHighOffset() const { return adcHighOffset; }
void SetLowOffset(int8_t p_offset) { adcLowOffset = p_offset; }
void SetHighOffset(int8_t p_offset) { adcHighOffset = p_offset; }
// For the theory behind ADC oversampling, see http://www.atmel.com/Images/doc8003.pdf
static const unsigned int AdcOversampleBits = 2; // we use 2-bit oversampling
void CalcDerivedParameters(); // calculate shA and shB
// The following are configurable parameters
float r25, beta, shC, seriesR; // parameters declared in the M305 command
int8_t adcLowOffset, adcHighOffset; // ADC low and high end offsets
// The following are derived from the configurable parameters
float shA, shB; // derived parameters
static const unsigned int AdcBits = 12; // the ADCs in the SAM processors are 12-bit
static const int32_t AdcRange = 1 << (AdcBits + AdcOversampleBits); // The readings we pass in should be in range 0..(AdcRange - 1)
};
#endif /* SRC_HEATING_THERMISTOR_H_ */
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