From d50a3c902a5a0b60dd0f820fa01a64fad48a0c3c Mon Sep 17 00:00:00 2001
From: PhysicistJohn <54456354+PhysicistJohn@users.noreply.github.com>
Date: Tue, 14 Jul 2026 22:04:58 -0700
Subject: [PATCH] fix: initialize complete backup checksum image

The RTC backup checksum covers every byte except the checksum itself, including a reserved packed byte that was never assigned. Its stack value could therefore make otherwise valid state fail verification after reset.

Zero-initialize the complete backup image before assigning persisted fields so the checksum and reserved byte are deterministic.
---
 main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/main.c b/main.c
index 09fc658..745074a 100644
--- a/main.c
+++ b/main.c
@@ -161,7 +161,8 @@ static THD_FUNCTION(Thread1, arg)
   while (1) {
 //  START_PROFILE
     if (sweep_mode&(SWEEP_ENABLE|SWEEP_ONCE)) {
-      backup_t b;
+      /* Initialize the reserved byte covered by the checksum too. */
+      backup_t b = {0};
       b.data.frequency0 = setting.frequency0;
       b.data.frequency1 = setting.frequency1;
       if (setting.auto_attenuation)