Add PPS capture message to logged topics, simplify timestamp logic and small cleanup

src/drivers/pps_capture/PPSCapture.cpp

@@ -99,14 +99,12 @@ void PPSCapture::Run()
 	pps_capture_s pps_capture;
 	pps_capture.timestamp = _hrt_timestamp;
 	// GPS UTC time when the GPIO interrupt was triggered
-	// UTC time + elapsed time since the UTC time was received - eleapsed time since the PPS interrupt
-	// event
-	uint64_t gps_utc_time = _last_gps_utc_timestamp + hrt_elapsed_time(&_last_gps_timestamp)
-				- hrt_elapsed_time(&_hrt_timestamp);
+	// Last UTC time received from the GPS + elapsed time to the PPS interrupt
+	uint64_t gps_utc_time = _last_gps_utc_timestamp + (_hrt_timestamp - _last_gps_timestamp);
 
 	// (For ubx F9P) The rising edge of the PPS pulse is aligned to the top of second GPS time base.
 	// So, remove the fraction of second and shift to the next second. The interrupt is triggered
-	// before the matching timestamp tranfered, which means the last received GPS time is always
+	// before the matching timestamp is received via a UART message, which means the last received GPS time is always
 	// behind.
 	pps_capture.rtc_timestamp = gps_utc_time - (gps_utc_time % USEC_PER_SEC) + USEC_PER_SEC;
 

src/drivers/pps_capture/PPSCapture.hpp

@@ -73,12 +73,9 @@ private:
 	uORB::Publication<pps_capture_s>	_pps_capture_pub{ORB_ID(pps_capture)};
 	uORB::Subscription								_sensor_gps_sub{ORB_ID(sensor_gps)};
 
-	static constexpr unsigned USEC_IN_1_SEC{1000000}; // microseconds in 1 second
-	static constexpr unsigned MAX_POSITIVE_DRIFT{USEC_IN_1_SEC / 2}; // microseconds
-
 	hrt_abstime _hrt_timestamp{0};
 
-	uint64_t _last_gps_timestamp{0};
-	uint64_t _last_gps_utc_timestamp{0};
+	hrt_abstime	_last_gps_timestamp{0};
+	uint64_t		_last_gps_utc_timestamp{0};
 
 };