From b9b94fcadc6a6deaffe16c613446b02d6da41095 Mon Sep 17 00:00:00 2001
From: rusefillc <48498823+rusefillc@users.noreply.github.com>
Date: Sat, 7 May 2022 14:12:20 -0400
Subject: [PATCH] Temperature (#63)

* integer id interpolation

* Calculate sensor temperature based on Ri

* Sensor Ri around 25C

Co-authored-by: Andrey Gusakov <dron0gus@gmail.com>
---
 firmware/Makefile          |  1 +
 firmware/interpolation.cpp | 37 +++++++++++++++++++++++++++++++++++++
 firmware/interpolation.h   | 10 ++++++++++
 firmware/sampling.cpp      | 27 +++++++++++++++++++++++++++
 firmware/sampling.h        |  1 +
 5 files changed, 76 insertions(+)
 create mode 100644 firmware/interpolation.cpp
 create mode 100644 firmware/interpolation.h

diff --git a/firmware/Makefile b/firmware/Makefile
index 92bfbc9..795f7bc 100644
--- a/firmware/Makefile
+++ b/firmware/Makefile
@@ -144,6 +144,7 @@ CPPSRC = $(ALLCPPSRC) \
           pid.cpp \
           pump_control.cpp \
           uart.cpp \
+          interpolation.cpp \
           main.cpp
 
 # List ASM source files here.
diff --git a/firmware/interpolation.cpp b/firmware/interpolation.cpp
new file mode 100644
index 0000000..2f99e12
--- /dev/null
+++ b/firmware/interpolation.cpp
@@ -0,0 +1,37 @@
+#include "interpolation.h"
+
+int interpolateInt(int x1, int y1, int x2, int y2, int x)
+{
+	if (x1 == x2)
+		return y1;
+
+	return (y1 + (y2 - y1) * (x - x1) / (x2 - x1));
+}
+
+int interpolateIntClamped(int x1, int y1, int x2, int y2, int x)
+{
+	if (x <= x1)
+		return y1;
+	if (x >= x2)
+		return y2;
+
+	return interpolateInt(x1, y1, x2, y2, x);
+}
+
+int interpolate_1d_int(const struct inter_point *p, int size, int x)
+{
+	int i;
+
+	/* no exterpolation */
+	if (x < p[0].x)
+		return p[0].y;
+
+	for (i = 0; i < size - 1; i++) {
+		if ((x >= p[i].x) && (x < p[i + 1].x)) {
+			return interpolateInt(p[i].x, p[i].y, p[i + 1].x, p[i + 1].y, x);
+		}
+	}
+
+	/* no exterpolation */
+	return p[size - 1].y;
+}
diff --git a/firmware/interpolation.h b/firmware/interpolation.h
new file mode 100644
index 0000000..aa79d25
--- /dev/null
+++ b/firmware/interpolation.h
@@ -0,0 +1,10 @@
+#pragma once
+
+struct inter_point {
+	int		x;
+	int		y;
+};
+
+int interpolateInt(int x1, int y1, int x2, int y2, int x);
+int interpolateIntClamped(int x1, int y1, int x2, int y2, int x);
+int interpolate_1d_int(const struct inter_point *p, int size, int x);
diff --git a/firmware/sampling.cpp b/firmware/sampling.cpp
index 4810e8a..8ea72e7 100644
--- a/firmware/sampling.cpp
+++ b/firmware/sampling.cpp
@@ -1,4 +1,5 @@
 #include "sampling.h"
+#include "interpolation.h"
 
 #include "ch.h"
 #include "hal.h"
@@ -14,6 +15,27 @@ static float nernstDc = 0;
 static float pumpCurrentSenseVoltage = 0;
 static float internalBatteryVoltage = 0;
 
+static const struct inter_point lsu49_r_to_temp[] =
+{
+    {   80, 1030},
+    {  150,  890},
+    {  200,  840},
+    {  250,  805},
+    {  300,  780},
+    {  350,  760},
+    {  400,  745},
+    {  450,  730},
+    {  550,  705},
+    {  650,  685},
+    {  800,  665},
+    { 1000,  640},
+    { 1200,  630},
+    { 2500,  565},
+    { 6000,   25}   /* measured while cold */
+};
+
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+
 constexpr float f_abs(float x)
 {
     return x > 0 ? x : -x;
@@ -86,6 +108,11 @@ float GetSensorInternalResistance()
     return totalEsr - VM_RESISTOR_VALUE;
 }
 
+float GetSensorTemperature()
+{
+    return interpolate_1d_int(lsu49_r_to_temp, ARRAY_SIZE(lsu49_r_to_temp), GetSensorInternalResistance());
+}
+
 float GetNernstDc()
 {
     return nernstDc;
diff --git a/firmware/sampling.h b/firmware/sampling.h
index 34c796d..e376e05 100644
--- a/firmware/sampling.h
+++ b/firmware/sampling.h
@@ -4,6 +4,7 @@ void StartSampling();
 
 float GetNernstAc();
 float GetSensorInternalResistance();
+float GetSensorTemperature();
 float GetNernstDc();
 
 float GetPumpNominalCurrent();