From 5eef8dc91921e89cf20e0b738d9f23199de755f1 Mon Sep 17 00:00:00 2001
From: c vw <dl1ycf@darc.de>
Date: Thu, 10 Jun 2021 12:38:45 +0200
Subject: [PATCH] Avoid division by zero when calculating SWR
---
transmitter.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/transmitter.c b/transmitter.c
index d751cbf..6d4dcd5 100644
--- a/transmitter.c
+++ b/transmitter.c
@@ -570,6 +570,7 @@ static gboolean update_display(gpointer data) {
fwd_average=fwd_average-fwd_cal_offset;
rev_average=rev_average-fwd_cal_offset;
if (rev_average < 0) rev_average=0;
+ if (fwd_average < 0) fwd_average=0;
break;
case NEW_PROTOCOL:
@@ -634,6 +635,7 @@ static gboolean update_display(gpointer data) {
fwd_average=fwd_average-fwd_cal_offset;
rev_average=rev_average-fwd_cal_offset;
if (rev_average < 0) rev_average=0;
+ if (fwd_average < 0) fwd_average=0;
break;
@@ -663,8 +665,10 @@ static gboolean update_display(gpointer data) {
// tx->swr can be used in other parts of the program to
// implement SWR protection etc.
// The SWR is calculated from the (time-averaged) forward and reverse voltages.
+ // Take care that no division by zero can happen, since otherwise the moving
+ // exponential average cannot survive from a "nan".
//
- if (tx->fwd > 0.1) {
+ if (tx->fwd > 0.1 && fwd_average > 0.01) {
//
// SWR means VSWR (voltage based) but we have the forward and
// reflected power, so correct for that
--
2.45.2