public async void StopTimer()
        {
            // pag di enabled, return lng
            if (!IsEnabled)
            {
                return;
            }

            // enabled, so pwede i-stop
            IsEnabled = false;

            // get time when stopped
            stopTime    = DateTime.Now;
            stopTimeStr = stopTime.ToLongTimeString();
            activity.SetStopTime(stopTimeStr);

            // pagkastop write ulit last
            await WriteEntries();

            // create model TODO
            AccelerometerRecord record = new AccelerometerRecord()
            {
                Filename  = currentFilename,
                ClientId  = cliSession.ClientId,
                StartTime = startTime,
                StopTime  = stopTime
            };

            Logger.Debug(record);

            // save to db
            var response = await cliService.AddAccelerometerRecord(record);
        }