embedded code copied from jankae/VNA and adjusted for STM32G4

Software/VNA_embedded/Application/Drivers/algorithm.cpp

@@ -0,0 +1,44 @@
+#include "algorithm.hpp"
+
+#include "stm.hpp"
+#include <cmath>
+
+Algorithm::RationalApproximation Algorithm::BestRationalApproximation(float ratio, uint32_t max_denom) {
+	RationalApproximation result;
+	uint32_t a = 0, b = 1, c = 1, d = 1;
+	while (b + d <= max_denom) {
+		auto mediant = (float) (a + c) / (b + d);
+		if (ratio == mediant) {
+			if (b + d <= max_denom) {
+				result.num = a + c;
+				result.denom = b + d;
+				return result;
+			} else if (d > b) {
+				result.num = c;
+				result.denom = d;
+				return result;
+			} else {
+				result.num = a;
+				result.denom = b;
+				return result;
+			}
+		} else if (ratio > mediant) {
+			a = a + c;
+			b = b + d;
+		} else {
+			c = a + c;
+			d = b + d;
+		}
+	}
+	// check which of the two is the better solution
+	float dev_ab = (float) a / b - ratio;
+	float dev_cd = (float) c / d - ratio;
+	if(fabs(dev_cd) < fabs(dev_ab)) {
+		result.num = c;
+		result.denom = d;
+	} else {
+		result.num = a;
+		result.denom = b;
+	}
+	return result;
+}