From 8cf17dc774b44a37c075a9117cf492ab8e103913 Mon Sep 17 00:00:00 2001
From: BlackMark <me@blackmark.me>
Date: Sun, 29 Mar 2020 06:20:21 +0200
Subject: [PATCH] Implement temperature calculation

---
 thermistor/main.cpp           |  48 +++++++-
 thermistor/thermistor.cppproj | 218 +++++++++++++++++-----------------
 2 files changed, 157 insertions(+), 109 deletions(-)

diff --git a/thermistor/main.cpp b/thermistor/main.cpp
index d87c722..d8ccdc6 100644
--- a/thermistor/main.cpp
+++ b/thermistor/main.cpp
@@ -1,6 +1,8 @@
 #include "clock.hpp"
 
+#include <math.h>
 #include <stdint.h>
+#include <stdio.h>
 
 #include "flash/flash.hpp"
 #include "io/io.hpp"
@@ -12,6 +14,38 @@
 #define UART0_INT_VECTORS
 #include "uart/hardware0.hpp"
 
+static constexpr auto SERIES_RESISTOR = 9951;
+static constexpr auto THERMISTOR_NOMINAL = 9270;
+static constexpr auto BETA_COEFFICIENT = 3212;
+static constexpr auto NOMINAL_TEMPERATURE = 25;
+
+template <typename Adc>
+double sampleAdc(Adc &adcPin, uint16_t numSamples = 100)
+{
+	double samples = 0;
+
+	for (uint16_t i = 0; i < numSamples; ++i)
+		samples += adcPin.read();
+
+	return samples / numSamples;
+}
+
+double getResistance(double adcSample)
+{
+	return SERIES_RESISTOR * adcSample / (1023 - adcSample);
+}
+
+double getTemperature(double resistance)
+{
+	double steinhart = resistance / THERMISTOR_NOMINAL;
+	steinhart = log(steinhart);
+	steinhart /= BETA_COEFFICIENT;
+	steinhart += 1.0 / (NOMINAL_TEMPERATURE + 273.15);
+	steinhart = 1.0 / steinhart;
+	steinhart -= 273.15;
+	return steinhart;
+}
+
 int main()
 {
 	uart::Uart0<> serial;
@@ -25,8 +59,18 @@ int main()
 	adcPin.init();
 
 	while (true) {
-		auto adcSample = adcPin.read();
-		serial << F("Read ADC: ") << adcSample << F("\r\n");
+		const auto adcSample = sampleAdc(adcPin, 1000);
+		const auto thermistorResistance = getResistance(adcSample);
+		const auto temperature = getTemperature(thermistorResistance);
+
+		char floatBuffer[16];
+
+		sprintf(floatBuffer, "%.2f", adcSample);
+		serial << F("Read ADC: ") << floatBuffer << F("\r\n");
+		sprintf(floatBuffer, "%.2f", thermistorResistance);
+		serial << F("Resistance: ") << floatBuffer << F("\r\n");
+		sprintf(floatBuffer, "%.2f", temperature);
+		serial << F("Temperature: ") << floatBuffer << F(" C \r\n");
 
 		_delay_ms(1000);
 	}
diff --git a/thermistor/thermistor.cppproj b/thermistor/thermistor.cppproj
index 21b9891..65221a8 100644
--- a/thermistor/thermistor.cppproj
+++ b/thermistor/thermistor.cppproj
@@ -61,118 +61,122 @@
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