Howto Boot Into Upgrade Mode
There are many different ways to boot into upgrade mode listed as following:
Usually, the first two methods will meet most of the user needs, but in some case, for example, if burnning a wrong u-boot, or your device cannot even boot any more, in thus cases, you can try with MRegister mode.
Keys Mode(U-Boot is running)
Power on Vim. Long press Power key without release Short press ‘Reset’ key and release Count 2-3 seconds and release the ‘Power’ key to enter into upgrade mode
Serial Mode(For developers)
Refer this guidance to setup serial tool for Vim. Make sure again you've done the right connections and setup. Hit any keys at the moment of booting to stop autoboot. This step will let Vim boot into u-boot mode. Type update on the terminal of u-boot as belowing:
Vim# update 这里出不来。