Diff: thermistor.cpp

Revision:

0:854742598c2c

Child:

1:851dbb04c1e5

diff -r 000000000000 -r 854742598c2c thermistor.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/thermistor.cpp	Fri Feb 19 16:05:58 2021 +0530
@@ -0,0 +1,87 @@
+/*!
+ *****************************************************************************
+  @file:  thermistor.cpp
+
+  @brief: Thermistor sensor module
+
+  @details:
+ -----------------------------------------------------------------------------
+ Copyright (c) 2020 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 <math.h>
+#include "thermistor.h"
+
+/******************************************************************************/
+/************************** Functions Definitions *****************************/
+/******************************************************************************/
+
+thermistor::thermistor() {};
+thermistor::~thermistor() {};
+
+/*!
+ * @brief	Convert the thermistor resistance into equivalent temperature
+ * @param	resistance[in]- Thermistor resistance (Rth)
+ * @param	coeff_A[in] - A coefficient for conversion
+ * @param	coeff_B[in] - B coefficient for conversion
+ * @param	coeff_C[in] - C coefficient for conversion
+ * @return	Thermistor temperature value
+ * @note	This function uses Steinhart-Hart equation for converting Thermistor
+ *			resistance into temperature. Refer below design note for more details:
+ *			https://www.analog.com/en/design-center/reference-designs/circuits-from-the-lab/cn0545.html
+ */
+float thermistor::convert(const float resistance, float coeff_A, float coeff_B,
+			  float coeff_C)
+{
+	float temperature = 25.0;
+
+	/* Get temperature into celcius */
+	temperature = 1 / (coeff_A + (coeff_B * log(resistance)) + (coeff_C * pow(log(
+				   resistance), 3)));
+	temperature -= 273.15;
+
+	return temperature;
+}
+
+
+/*!
+ * @brief	Convert the thermistor resistance into equivalent temperature using
+ *			lookup table
+ * @param	lut[in]- Pointer to look-up table
+ * @param	resistance[in] - thermistor resistance
+ * @param	size[in] - look-up table size
+ * @param	offset[in] - look-up table offset
+ * @return	Thermistor temperature value
+ */
+float thermistor::lookup(const uint32_t *lut, uint32_t resistance,
+			 uint16_t size, int16_t offset)
+{
+	uint16_t first = 0;
+	uint16_t last = size - 1;
+	uint16_t middle = (first + last) / 2;
+
+	while (first <= last) {
+		if (resistance < lut[middle])
+			first = middle + 1;
+		else if (lut[middle] == resistance) {
+			return static_cast<float>(middle + offset);
+		} else
+			last = middle - 1;
+
+		middle = (first + last) / 2;
+	}
+
+	if (first > last)
+		return static_cast<float>(first + offset);
+
+	return 0; // should never get here
+}