USB flash drive upgrade steps and precautions:

1. Prepare a USB flash drive in fat32 format;
2. Put the USB flash drive upgrade package (update.zip) into the root directory of USB flash drive;
3. Insert the USB flash drive into the machine and wait for about 20 seconds.
An upgrade window will pop up on the interface.

Note:
1. Do not unplug the USB flash drive during the upgrade process. The machine should not be powered off.
2. Fat32 format is required for U disk;
3. The upgrade package cannot be identified until it is placed in the root directory of the U disk;
4. Make sure the power is above 30%, otherwise the upgrade may be unsuccessful;