I plugged in a USB drive with a gcode file, and SM2 is not recognizing the drive. It says the USB drive size is zero with no files in it. Clearly this sounds like a drive failuire, except that it works fine on a regular computer.
I saw in the discussion group that the SM2 comes with a flash thumb drive. I do not recall seeing such a thing in my package.
I also tried plugging in my Android phone via a USB cable, and enabled file transfer. Normally the host should recognize it as a storage device. SM2 did not recognize it as a drive in this case.
The only way I could upload my gcode was from a laptop running SM Luban software and connecting over wifi.