From e0c9f4dcee8672866fa0f6df0ef8eec6a148da02 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jan=20K=C3=A4berich?= <j.kaeberich@gmx.de>
Date: Sat, 13 Nov 2021 19:32:58 +0100
Subject: [PATCH] Fix fractional calculation for frequencies close to integer
 multiples

---
 Software/VNA_embedded/Application/Drivers/max2871.cpp | 8 ++++++++
 Software/VNA_embedded/Application/VNA.cpp             | 6 ++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/Software/VNA_embedded/Application/Drivers/max2871.cpp b/Software/VNA_embedded/Application/Drivers/max2871.cpp
index 9781898..54fa29b 100644
--- a/Software/VNA_embedded/Application/Drivers/max2871.cpp
+++ b/Software/VNA_embedded/Application/Drivers/max2871.cpp
@@ -190,6 +190,14 @@ bool MAX2871::SetFrequency(uint64_t f) {
 
 	auto approx = Algorithm::BestRationalApproximation(fraction, 4095);
 
+	if (approx.denom == approx.num) {
+		// got an impossible result due to floating point limitations(?)
+		// Set fractional part to zero, increase integer part instead
+		approx.num = 0;
+		approx.denom = 2;
+		N++;
+	}
+
 	if(approx.denom == 1) {
 		// M value must be at least 2
 		approx.denom = 2;
diff --git a/Software/VNA_embedded/Application/VNA.cpp b/Software/VNA_embedded/Application/VNA.cpp
index 9e0b4c3..65b0973 100644
--- a/Software/VNA_embedded/Application/VNA.cpp
+++ b/Software/VNA_embedded/Application/VNA.cpp
@@ -180,9 +180,11 @@ bool VNA::Setup(Protocol::SweepSettings s) {
 					// Configure LO2 for the changed IF1. This is not necessary right now but it will generate
 					// the correct clock settings
 					last_LO2 = actualFirstIF - HW::IF2;
-					LOG_INFO("Changing 2.LO to %lu at point %lu (%lu%06luHz) to reach correct 2.IF frequency",
+					LOG_INFO("Changing 2.LO to %lu at point %lu (%lu%06luHz) to reach correct 2.IF frequency (1.LO: %lu%06luHz, 1.IF: %lu%06luHz)",
 							last_LO2, i, (uint32_t ) (freq / 1000000),
-							(uint32_t ) (freq % 1000000));
+							(uint32_t ) (freq % 1000000), (uint32_t ) (actualLO1 / 1000000),
+							(uint32_t ) (actualLO1 % 1000000), (uint32_t ) (actualFirstIF / 1000000),
+							(uint32_t ) (actualFirstIF % 1000000));
 				} else {
 					// last entry in IF table, revert LO2 to default
 					last_LO2 = HW::IF1 - HW::IF2;