From ece7fb2b733c81001b8a8588914d14df42cc90b8 Mon Sep 17 00:00:00 2001
From: daijoubu <daijoubu@gmail.com>
Date: Tue, 14 Jul 2026 20:26:03 -0700
Subject: [PATCH] dronecan: log cumulative bus-off count to blackbox slow frame

Adds droneCANBusOffCount to the blackbox S-frame, sourced from the
existing dronecanGetBusOffCount() counter, so intermittent CAN bus
faults are diagnosable from flight logs instead of requiring a live
`dronecan` CLI session. TEC/REC/LEC/state and RX-drop-count were
considered and dropped/deferred (see PLAN.md) as poor fits for the
slow frame's throttled, change-triggered sampling model.
---
 src/main/blackbox/blackbox.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/main/blackbox/blackbox.c b/src/main/blackbox/blackbox.c
index 75ab075feac..2ea27307e1c 100644
--- a/src/main/blackbox/blackbox.c
+++ b/src/main/blackbox/blackbox.c
@@ -83,7 +83,9 @@
 #include "sensors/esc_sensor.h"
 #include "flight/wind_estimator.h"
 #include "sensors/temperature.h"
-
+#ifdef USE_DRONECAN
+#include "drivers/dronecan/dronecan.h"
+#endif
 
 #if defined(ENABLE_BLACKBOX_LOGGING_ON_SPIFLASH_BY_DEFAULT)
 #define DEFAULT_BLACKBOX_DEVICE     BLACKBOX_DEVICE_FLASH
@@ -470,6 +472,9 @@ static const blackboxSimpleFieldDefinition_t blackboxSlowFields[] = {
     {"escRPM",                -1, UNSIGNED, PREDICT(0),             ENCODING(UNSIGNED_VB)},
     {"escTemperature",        -1, SIGNED,   PREDICT(PREVIOUS),      ENCODING(SIGNED_VB)},
 #endif
+#ifdef USE_DRONECAN
+    {"droneCANBusOffCount",   -1, UNSIGNED, PREDICT(0),      ENCODING(UNSIGNED_VB)},
+#endif
 };
 
 #define BLACKBOX_FIRST_HEADER_SENDING_STATE BLACKBOX_STATE_SEND_HEADER
@@ -579,6 +584,9 @@ typedef struct blackboxSlowState_s {
 #endif
     uint16_t rxUpdateRate;
     uint8_t activeWpNumber;
+#ifdef USE_DRONECAN
+    uint32_t droneCANBusOffCount;
+#endif
 } __attribute__((__packed__)) blackboxSlowState_t; // We pack this struct so that padding doesn't interfere with memcmp()
 
 //From rc_controls.c
@@ -1365,6 +1373,10 @@ static void writeSlowFrame(void)
     blackboxWriteSignedVB(slowHistory.escTemperature);
 #endif
 
+#ifdef USE_DRONECAN
+    blackboxWriteUnsignedVB(slowHistory.droneCANBusOffCount);
+#endif
+
     blackboxSlowFrameIterationTimer = 0;
 }
 
@@ -1439,6 +1451,10 @@ static void loadSlowState(blackboxSlowState_t *slow)
     slow->escRPM = escSensor->rpm;
     slow->escTemperature = escSensor->temperature;
 #endif
+
+#ifdef USE_DRONECAN
+    slow->droneCANBusOffCount = dronecanGetBusOffCount();
+#endif
 }
 
 /**