Can't get USB to work correctly

[mikefromsac]

I just received my DM42. I set the time and date and keyed in a short program (8 steps). All works great.

I then tried to add a program via the USB connection. The first time I tried, there was no "Program" folder on the calculator. When I ejected the calculator and then unplugged the cable, the whole calculator was reset to factory specs and it seemed to be reinstalling the operating system. No time or day setting were saved and my program was gone.

So I set the time and date and hand-typed the short program again, and then connected the USB again. This time there was a "Program" folder in the drive, so I copied the larger program I wanted to add to the DM42, but after ejecting the calculator, the same thing happened. Everything was reset to factory with no settings saved and no programs.

Any ideas?

[mikefromsac]

Now all the calculator folders show up on my computer. Maybe the USB needed a little scrubbing by having a cable inserted a few times? No matter ... all good and love this calculator.

[svarre69]

Hi!

You have to be very carefull when using the USB connection. Because of the shape of the DM42 the cable cannot be fully inserted into the socket. However this seldom give problems - when you know of it.

And furthermore it needs to be a data transfer micro USB cable - not just a charging cable.

Use the USB eject feature on the PC and the Exit function on the DM42, before disconnecting the data transfer cable. Never just pull out the cable, since it can damage the file system.

All the best
Peter

[Thomas_ER]

more infos about slightly modifying / shaping the USB plug
at viewtopic.php?f=18&t=290

[ijabbott]

Some Micro-B cables seem to have longer plugs, i.e. they stick out from the plastic moulding more. Use those.

[nephilim]

I am not sure anymore it's the cable. I got a cable with longer connector which yields a very secure fit. A minute ago I connected the DM42, tidied up the offimg folder, ejected, saved a state file and then decided to do a full backup. So I connected again and started to copy files. The DM42 disconnected while copying the content of the offimg folder and has now to be reset. I am sure this time it was not the cable.

I also wonder why in such a situation (copy from DM42) the FAT partition is wiped. Does the hardware reset button on the back cause the wiping? If so is it possible to implement a "soft" reset which restarts the device?

[EM41]

A hard disconnect can corrupt the FAT drive, had this a few times with a particular bad USB cable.
A reset should be no problem.
If there is anything important on the disk you may want to recover you can use photorec.
I runs it under linux but it seems to be also available for windows now https://www.cgsecurity.org/wiki/TestDisk_Download
Its very effective even for disks you consider lost forever.