Diff: app/ad7124_temperature_sensor.cpp

Revision:

1:c863d7e9e272

Child:

3:f20f09251190

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/ad7124_temperature_sensor.cpp	Mon Feb 22 05:13:58 2021 +0000
@@ -0,0 +1,262 @@
+
+/***************************************************************************//*
+ * @file    ad7124_temperature_sensor.cpp
+ * @brief   AD7124 temperature sensor functionality
+ * @details
+******************************************************************************
+ * Copyright (c) 2021 Analog Devices, Inc. All Rights Reserved.
+ *
+ * This software is proprietary to Analog Devices, Inc. and its licensors.
+ * By using this software you agree to the terms of the associated
+ * Analog Devices Software License Agreement.
+******************************************************************************/
+
+/******************************************************************************/
+/***************************** Include Files **********************************/
+/******************************************************************************/
+
+#include <stdint.h>
+#include <math.h>
+
+#include <thermocouple.h>
+#include <ptxxx.h>
+#include <ntc_10k_44031.h>
+#include <ptc_ky81_110.h>
+
+#include "ad7124_temperature_sensor.h"
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif //  _cplusplus
+
+#include "ad7124_regs_configs.h"
+#include "ad7124_support.h"
+
+#ifdef __cplusplus  // Closing extern c
+}
+#endif //  _cplusplus
+
+/******************************************************************************/
+/********************* Macros and Constants Definitions ***********************/
+/******************************************************************************/
+
+/* NTC thermistor Rsense value (in ohms) */
+#define NTC_RSENSE			10000
+
+/* PTC thermistor Ref Resistance value (in ohms) */
+#define PTC_RREF			5110
+
+/******************************************************************************/
+/******************** Variables and User Defined Data Types *******************/
+/******************************************************************************/
+
+/* Calibration constant (iout ratio) for RTD resistance measurement */
+static float calibration_iout_ratio = 1;
+
+/******************************************************************************/
+/************************** Functions Definitions *****************************/
+/******************************************************************************/
+
+/*!
+ * @brief	Convert the ADC raw value into equivalent RTD resistance
+ * @param	adc_raw[in]- ADC raw sample
+ * @return	RTD resistance value
+ * @note	RTD is biased with constant excitation current. Below formula
+ *			is based on ratiometric measurement, where fixed value of RTD RREF
+ *			(reference resistor) and gain is taken into account
+ */
+static float convert_adc_raw_into_rtd_resistance(int32_t adc_raw)
+{
+	float rtd_res;
+
+	/* Below equation is for bipolar inputs as all ADC configurations for
+	 * sensor measurement are having default bipolar mode */
+	rtd_res = (((float)adc_raw - (1 << (AD7124_ADC_N_BITS - 1))) *
+		   (calibration_iout_ratio * RTD_RREF)) / ((
+					   AD7124_PGA_GAIN(RTD_GAIN_VALUE)) * (1 << (AD7124_ADC_N_BITS - 1)));
+
+	return rtd_res;
+}
+
+
+/*!
+ * @brief	Store the RTD calibration Iout ratio for 3-wire RTD calibration
+ *			based measurement
+ * @param	iout_ratio[in]- Iout1/Iout0 ratio
+ * @param	status[in] - Calibration ratio set/reset flag
+ * @return	none
+ */
+void store_rtd_calibrated_iout_ratio(float iout_ratio, bool status)
+{
+	if (status) {
+		calibration_iout_ratio = 1 + iout_ratio;
+	} else {
+		calibration_iout_ratio = 1;
+	}
+}
+
+
+/*!
+ * @brief	Convert the ADC raw value into equivalent PTC thermistor resistance
+ * @param	adc_raw[in]- ADC raw sample
+ * @return	PTC resistance value
+ * @note	PTC is biased with constant excitation current. Below formula
+ *			is based on ratiometric measurement, where fixed value of PTC RREF
+ *			(reference resistor) and gain is taken into account
+ */
+static float convert_adc_raw_into_ptc_resistance(int32_t adc_raw)
+{
+	float ptc_res;
+
+	/* Below equation is for bipolar inputs as all ADC configurations for
+	 * sensor measurement are having default bipolar mode */
+	ptc_res = (((float)adc_raw - (1 << (AD7124_ADC_N_BITS - 1))) * PTC_RREF) / ((
+				AD7124_PGA_GAIN(THERMISTOR_GAIN_VALUE)) * (1 << (AD7124_ADC_N_BITS - 1)));
+
+	return ptc_res;
+}
+
+
+/*!
+ * @brief	Convert the ADC raw value into equivalent NTC thermistor voltage
+ * @param	adc_raw[in]- ADC raw sample
+ * @return	NTC Thermistor voltage value
+ * @note	The NTC is biased with constant ADC reference voltage. Below formula
+ *			is based on ratiometric measurement, where fixed value of ADC REF
+ *			and gain is taken into account
+ */
+static float convert_adc_raw_into_ntc_voltage(int32_t adc_raw)
+{
+	float ntc_voltage;
+
+	/* Below equation is for bipolar inputs as all ADC configurations for
+	 * sensor measurement are having default bipolar mode */
+	ntc_voltage = (((float)adc_raw - (1 << (AD7124_ADC_N_BITS - 1))) *
+		       AD7124_REF_VOLTAGE) / ((
+				       AD7124_PGA_GAIN(THERMISTOR_GAIN_VALUE)) * (1 << (AD7124_ADC_N_BITS - 1)));
+
+	return ntc_voltage;
+}
+
+
+/*!
+ * @brief	Convert the NTC thermistor voltage into equivalent resistance
+ * @param	voltage[in]- NTC Thermistor voltage
+ * @return	NTC Thermistor resistance value
+ */
+static float convert_ntc_voltage_into_resistance(float ntc_voltage)
+{
+	float ntc_resistance = (ntc_voltage * NTC_RSENSE) / (AD7124_REF_VOLTAGE -
+			       ntc_voltage);
+	return ntc_resistance;
+}
+
+
+/**
+ * @brief  	Converts raw ADC code to millivolts
+ * @param	raw_adc_code[in] Raw ADC code
+ * @return	voltage in millivolts
+ * @details	This converts the raw ADC code to millivolts for thermocouple channel,
+ *          based on the AD7124 Eval board configuration
+ */
+static float convert_raw_adc_into_tc_mv(uint32_t raw_adc_code)
+{
+	return (((((float)raw_adc_code - (1 << (AD7124_ADC_N_BITS - 1))) /
+		  (AD7124_PGA_GAIN(THERMOCOUPLE_GAIN_VALUE) *
+		   (1 << (AD7124_ADC_N_BITS - 1)))) * AD7124_REF_VOLTAGE) * 1000);
+}
+
+
+/**
+ * @brief  	Convert ADC raw value into TC temperature
+ * @param	tc_sample[in] Raw TC sample
+ * @param	cjc_sample[in] Raw CJC sample
+ * @param	cjc_sensor[in] CJC sensor type
+ * @return	TC temperature
+ */
+float get_tc_temperature(float tc_sample, float cjc_sample,
+			 cjc_sensor_type cjc_sensor)
+{
+	Thermocouple_Type_T tcSensor;
+	float tc_mv;
+	float tc_temperature;
+	float cjc_temperature;
+
+	tc_mv = convert_raw_adc_into_tc_mv(tc_sample);
+	tc_temperature = tcSensor.convert(tc_mv);
+
+	if (cjc_sensor == PT100_4WIRE_RTD) {
+		cjc_temperature = get_rtd_temperature(cjc_sample);
+	} else if (cjc_sensor == THERMISTOR_PTC_KY81_110) {
+		cjc_temperature = get_ptc_thermistor_temperature(cjc_sample);
+	} else if (cjc_sensor == PT1000_4WIRE_RTD) {
+		PT1000 rtd_sensor;
+		float rtd_resistance;
+
+		rtd_resistance = convert_adc_raw_into_rtd_resistance(cjc_sample);
+		cjc_temperature = rtd_sensor.convertResistanceToTemperature(rtd_resistance);
+	} else {
+		return 0;
+	}
+
+	/* NOTE The simplest approach of adding the CJC temperature to TC temperature is taken here.
+	 * A better method is to convert RTD back to thermocouple mV, and add that to TC value
+	 * then do the thermocouple to degC conversion.
+	 * */
+	return (tc_temperature + cjc_temperature);
+}
+
+
+/**
+ * @brief  	Convert ADC raw value into RTD temperature
+ * @param	rtd_sample[in] Raw RTD sample
+ * @return	RTD temperature
+ * @note	Fixed PT100 RTD sensor is used
+ */
+float get_rtd_temperature(int32_t rtd_sample)
+{
+	PT100 rtd_sensor;
+	float rtd_resistance;
+
+	rtd_resistance = convert_adc_raw_into_rtd_resistance(rtd_sample);
+
+	return rtd_sensor.convertResistanceToTemperature(rtd_resistance);
+}
+
+
+/**
+ * @brief  	Convert ADC raw value into NTC temperature
+ * @param	ntc_sample[in] Raw NTC sample
+ * @return	NTC temperature
+ * @note	Fixed NTC 10K 44031RC sensor is used
+ */
+float get_ntc_thermistor_temperature(int32_t ntc_sample)
+{
+	ntc_10k_44031rc ntc_thermistor;
+	float ntc_voltage;
+	float ntc_resistance;
+
+	ntc_voltage = convert_adc_raw_into_ntc_voltage(ntc_sample);
+	ntc_resistance = convert_ntc_voltage_into_resistance(ntc_voltage);
+
+	return ntc_thermistor.convert(ntc_resistance);
+}
+
+
+/**
+ * @brief  	Convert ADC raw value into PTC temperature
+ * @param	ptc_sample[in] Raw PTC sample
+ * @return	PTC temperature
+ * @note	Fixed PTC KY81/110 Thermistor sensor is used
+ */
+float get_ptc_thermistor_temperature(int32_t ptc_sample)
+{
+	ptc_ky81_110 ptc_thermistor;
+	float ptc_resistance;
+
+	ptc_resistance = convert_adc_raw_into_ptc_resistance(ptc_sample);
+
+	return ptc_thermistor.convert(ptc_resistance);
+}
+