logger: new optional start delay time (SDLOG_DELAY_S)

- this can be useful when using PX4 as a standalone data logger

src/drivers/drv_hrt.h

@@ -61,6 +61,8 @@ __BEGIN_DECLS
  */
 typedef uint64_t	hrt_abstime;
 
+#define HRT_ABSTIME_INVALID UINT64_MAX
+
 /**
  * Callout function type.
  *

src/modules/logger/logger.cpp

@@ -1127,20 +1127,41 @@ bool Logger::should_start_logging()
 		}
 	}
 
+	const bool delayed_start = (_param_sdlog_delay_s.get() > 0);
+
+	if (delayed_start && (_start_requested_time != HRT_ABSTIME_INVALID)) {
+		desired_state = true;
+		updated = true;
+	}
+
 	desired_state = desired_state || _manually_logging_override;
 
 	// only start/stop if this is a state transition
 	if (updated && _prev_state != desired_state) {
-		_prev_state = desired_state;
 
 		if (desired_state) {
-
 			if (_should_stop_file_log) { // happens on quick stop/start toggling
 				_should_stop_file_log = false;
 				stop_log_file(LogType::Full);
 			}
 
-			return true;
+			if (delayed_start) {
+				if (_start_requested_time == HRT_ABSTIME_INVALID) {
+					_start_requested_time = hrt_absolute_time();
+
+					PX4_INFO("Delayed start in %" PRIi32 " seconds", _param_sdlog_delay_s.get());
+					return false;
+
+				} else if (hrt_elapsed_time(&_start_requested_time) > _param_sdlog_delay_s.get() * 1_s) {
+					_start_requested_time = HRT_ABSTIME_INVALID; // reset
+					_prev_state = true;
+					return true;
+				}
+
+			} else {
+				_prev_state = true;
+				return true;
+			}
 
 		} else {
 			// delayed stop: we measure the process loads and then stop
@@ -1150,6 +1171,8 @@ bool Logger::should_start_logging()
 			if ((MissionLogType)_param_sdlog_mission.get() != MissionLogType::Disabled) {
 				stop_log_file(LogType::Mission);
 			}
+
+			_prev_state = false;
 		}
 	}
 

src/modules/logger/logger.h

@@ -332,6 +332,8 @@ private:
 	bool						_manually_logging_override{false};
 	bool						_start_immediately{false};
 
+	hrt_abstime                                     _start_requested_time{HRT_ABSTIME_INVALID};
+
 	Statistics					_statistics[(int)LogType::Count];
 	hrt_abstime					_last_sync_time{0}; ///< last time a sync msg was sent
 
@@ -381,7 +383,8 @@ private:
 		(ParamInt<px4::params::SDLOG_PROFILE>) _param_sdlog_profile,
 		(ParamInt<px4::params::SDLOG_MISSION>) _param_sdlog_mission,
 		(ParamBool<px4::params::SDLOG_BOOT_BAT>) _param_sdlog_boot_bat,
-		(ParamBool<px4::params::SDLOG_UUID>) _param_sdlog_uuid
+		(ParamBool<px4::params::SDLOG_UUID>) _param_sdlog_uuid,
+		(ParamInt<px4::params::SDLOG_DELAY_S>) _param_sdlog_delay_s
 #if defined(PX4_CRYPTO)
 		, (ParamInt<px4::params::SDLOG_ALGORITHM>) _param_sdlog_crypto_algorithm,
 		(ParamInt<px4::params::SDLOG_KEY>) _param_sdlog_crypto_key,

src/modules/logger/params.c

@@ -176,6 +176,17 @@ PARAM_DEFINE_INT32(SDLOG_DIRS_MAX, 0);
  */
 PARAM_DEFINE_INT32(SDLOG_UUID, 1);
 
+/**
+ * Start delay
+ *
+ * Start delay in seconds, only enabled if > 0.
+ *
+ * @unit s
+ * @min 0
+ * @group SD Logging
+ */
+PARAM_DEFINE_INT32(SDLOG_DELAY_S, 0);
+
 /**
  * Logfile Encryption algorithm
  *