Merge pull request #936 from sherlockflight/blackbox-arm-beep

Fix Blackbox arming beep time logging

docs/Blackbox.md

@@ -203,9 +203,9 @@ flight problems like vibration or PID setting issues.
 
 The Blackbox starts recording data as soon as you arm your craft, and stops when you disarm.
 
-If your craft has a buzzer attached, a short beep will be played when you arm and recording begins. You can later use
+If your craft has a buzzer attached, you can use Cleanflight's arming beep to synchronize your Blackbox log with your
-this beep to synchronize your recorded flight video with the rendered flight data log (the beep is shown as a blue line
+flight video. Cleanflight's arming beep is a "long, short" pattern. The beginning of the first long beep will be shown 
-in the flight data log, which you can sync against the beep in your recorded audio track).
+as a blue line in the flight data log, which you can sync against your recorded audio track.
 
 You should wait a few seconds after disarming your craft to allow the Blackbox to finish saving its data.
 
@@ -224,8 +224,9 @@ minutes.
 ![Dataflash tab in Configurator](Screenshots/blackbox-dataflash.png)
 
 After downloading the log, be sure to erase the chip to make it ready for reuse by clicking the "erase flash" button.
-If you try to start recording a new flight when the dataflash is already full, the Blackbox will not make its regular
+
-arming beep and nothing will be recorded.
+If you try to start recording a new flight when the dataflash is already full, Blackbox logging will be disabled and
+nothing will be recorded.
 
 ## Converting logs to CSV or PNG
 After your flights, you'll have a series of flight log files with a .TXT extension. You'll need to decode these with

src/main/blackbox/blackbox.c

@@ -250,7 +250,6 @@ typedef enum BlackboxState {
     BLACKBOX_STATE_SEND_GPS_H_HEADERS,
     BLACKBOX_STATE_SEND_GPS_G_HEADERS,
     BLACKBOX_STATE_SEND_SYSINFO,
-    BLACKBOX_STATE_PRERUN,
     BLACKBOX_STATE_RUNNING,
     BLACKBOX_STATE_SHUTTING_DOWN
 } BlackboxState;
@@ -268,6 +267,8 @@ extern uint32_t currentTime;
 
 static BlackboxState blackboxState = BLACKBOX_STATE_DISABLED;
 
+static uint32_t blackboxLastArmingBeep = 0;
+
 static struct {
     uint32_t headerIndex;
 
@@ -684,6 +685,12 @@ void startBlackbox(void)
          */
         blackboxBuildConditionCache();
 
+        /*
+         * Record the beeper's current idea of the last arming beep time, so that we can detect it changing when
+         * it finally plays the beep for this arming event.
+         */
+        blackboxLastArmingBeep = getArmingBeepTimeMicros();
+
         blackboxSetState(BLACKBOX_STATE_SEND_HEADER);
     }
 }
@@ -1012,16 +1019,19 @@ void blackboxLogEvent(FlightLogEvent event, flightLogEventData_t *data)
     }
 }
 
-// Write the time of the last arming beep to the log as a synchronization point
+/* If an arming beep has played since it was last logged, write the time of the arming beep to the log as a synchronization point */
-static void blackboxLogArmingBeep()
+static void blackboxCheckAndLogArmingBeep()
 {
     flightLogEvent_syncBeep_t eventData;
 
-    // Get time of last arming beep (in system-uptime microseconds)
+    // Use != so that we can still detect a change if the counter wraps
-    eventData.time = getArmingBeepTimeMicros();
+    if (getArmingBeepTimeMicros() != blackboxLastArmingBeep) {
+        blackboxLastArmingBeep = getArmingBeepTimeMicros();
 
-    // Write the time to the log
+        eventData.time = blackboxLastArmingBeep;
-    blackboxLogEvent(FLIGHT_LOG_EVENT_SYNC_BEEP, (flightLogEventData_t *) &eventData);
+
+        blackboxLogEvent(FLIGHT_LOG_EVENT_SYNC_BEEP, (flightLogEventData_t *) &eventData);
+    }
 }
 
 /**
@@ -1082,14 +1092,9 @@ void handleBlackbox(void)
 
             //Keep writing chunks of the system info headers until it returns true to signal completion
             if (blackboxWriteSysinfo()) {
-                blackboxSetState(BLACKBOX_STATE_PRERUN);
+                blackboxSetState(BLACKBOX_STATE_RUNNING);
             }
         break;
-        case BLACKBOX_STATE_PRERUN:
-            blackboxSetState(BLACKBOX_STATE_RUNNING);
-
-            blackboxLogArmingBeep();
-        break;
         case BLACKBOX_STATE_RUNNING:
             // On entry to this state, blackboxIteration, blackboxPFrameIndex and blackboxIFrameIndex are reset to 0
 
@@ -1099,6 +1104,8 @@ void handleBlackbox(void)
                 loadBlackboxState();
                 writeIntraframe();
             } else {
+                blackboxCheckAndLogArmingBeep();
+
                 /* Adding a magic shift of "masterConfig.blackbox_rate_num - 1" in here creates a better spread of
                  * recorded / skipped frames when the I frame's position is considered:
                  */