Cannot download dataflash logs after power off the vehicle

Ground Control Software Mission Planner
1

I have been downloading data flash log using mavlink without problems on my Pixhawk. Recently, when I did the same thing, it says No log to download.

I then powered up the quad on the bench, changed to different flight modes, and WITHOUT unplugging the flight battery, I can download the dataflash logs. But once after I disconnect the flight battery, and also unplug the USB cable connecting Pixhawk to computer, when powering up again, I cannot download the logs.

Appreciate any help on this.
Arducopter 3.5.3 MP 1.3.52

2

Yestarday I had almost the same problem, when trying to download the logs with my quad without battery and only usb connection MP gave me a strange error I never saw “Error:System.TimeoutException: Timeout on read - GetLogEntry
at MissionPlanner.MAVLinkInterface.GetLogEntry(UInt16 startno, UInt16 endno) in C:\Users\michael\Source\Repos\MissionPlanner\Mavlink\MAVLinkInterface.cs:line 4565
at MissionPlanner.MAVLinkInterface.GetLogList() in C:\Users\michael\Source\Repos\MissionPlanner\Mavlink\MAVLinkInterface.cs:line 4505
at MissionPlanner.Log.LogDownloadMavLink.b__12_0() in C:\Users\michael\Source\Repos\MissionPlanner\Log\LogDownloadMavLink.cs:line 90”

As soon as I put the battery and switch on the drone, I’m able to download the logs as usual.

3

Try arming the drone before downloading the log. It works for me. It did
not require this some time ago.

4

I have been downloading data flash log using mavlink without problems on my
Pixhawk. Recently, when I did the same thing, it says No log to download.

I then powered up the quad on the bench, changed to different flight modes,
and WITHOUT unplugging the flight battery, I can download the dataflash
logs. But once after I disconnect the flight battery, and also unplug the
USB cable connecting Pixhawk to computer, when powering up again, I cannot
download the logs.

Are the logs present on the SD card after a reboot?

5

After a reboot, when I tried to download the log again, the message said
there is no file to download.

But I managed to download the logs before the power down.