In message 42C2050F.8050009@avantwave.com you wrote:

1. why uboot support downloading from Kermit rather than from minicom ?

U-Boot does not care for any special terminal emulation program; it supports download _protocols_, i. e. S-Record and kermit binary protocol.

Some terminal programs implement these protocols correctly and can be used with U-Boot, others have bugs or need non-trivial configurations, and are thus depracated.

It is more convinent if uboot can download from minicom.

Feel free to use minicom, but don't complain if you run into problems. Minicom is broken. You have been warned.

2.as topic , do uboot support downloading from USB ?

Yes.

wd