From d18b6072ba07af3a1efaa91633c434201bdd195a Mon Sep 17 00:00:00 2001
From: Leon Krieg <info@madcow.dev>
Date: Thu, 19 Sep 2024 15:11:32 +0200
Subject: [PATCH] Define conversion functions for TD, T and RH

---
 src/common.h      |  1 +
 src/common/math.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 src/common/math.h |  8 ++++++++
 3 files changed, 52 insertions(+)
 create mode 100644 src/common/math.c
 create mode 100644 src/common/math.h

diff --git a/src/common.h b/src/common.h
index f79b699..f1d0c78 100644
--- a/src/common.h
+++ b/src/common.h
@@ -1,6 +1,7 @@
 #ifndef MAD_CORE_COMMON_H
 #define MAD_CORE_COMMON_H
 
+#include "common/math.h"
 #include "common/types.h"
 #include "common/watchdog.h"
 
diff --git a/src/common/math.c b/src/common/math.c
new file mode 100644
index 0000000..be86f41
--- /dev/null
+++ b/src/common/math.c
@@ -0,0 +1,43 @@
+#include "common.h"
+
+// https://bmcnoldy.earth.miami.edu/Humidity.html
+// https://onlinelibrary.wiley.com/doi/abs/10.1002/andp.18280890511
+// https://onlinelibrary.wiley.com/doi/abs/10.1002/andp.18441370202
+
+// NOTE: EXP and LN are exponential and natural logarithm functions
+
+// Dewpoint TD
+// 243.04*(LN(RH/100)+((17.625*T)/(243.04+T)))/
+// (17.625-LN(RH/100)-((17.625*T)/(243.04+T)))
+float Dewp(float t, float rh)
+{
+	// TODO
+	UNUSED(tc);
+	UNUSED(rh);
+
+	return 0.0f;
+}
+
+// Temperature T
+// 243.04*(((17.625*TD)/(243.04+TD))-LN(RH/100))/
+// (17.625+LN(RH/100)-((17.625*TD)/(243.04+TD)))
+float Temp(float td, float rh)
+{
+	// TODO
+	UNUSED(dc);
+	UNUSED(rh);
+
+	return 0.0f;
+}
+
+// Relative Humidity RH
+// 100*(EXP((17.625*TD)/(243.04+TD))/
+//      EXP((17.625*T)/(243.04+T)))
+float Rhum(float t, float td)
+{
+	// TODO
+	UNUSED(tc);
+	UNUSED(dc);
+
+	return 0.0f;
+}
diff --git a/src/common/math.h b/src/common/math.h
new file mode 100644
index 0000000..624dd03
--- /dev/null
+++ b/src/common/math.h
@@ -0,0 +1,8 @@
+#ifndef MAD_CORE_COMMON_MATH_H
+#define MAD_CORE_COMMON_MATH_H
+
+float Dewp(float t, float rh);
+float Temp(float td, float rh);
+float Rhum(float t, float td);
+
+#endif // MAD_CORE_COMMON_MATH_H