I have some problems about building my own uboot

Dear all,
I try to build uboot and want to boot-up from SD card. I have several questions.
1.Could I use the /origin/master branch in git://git.denx.de/u-boot.git ?
2.Currently, my latest code is commit 73b6e6ad25 which the commit date is Nov. 4 2019
Could I use the config file /configs/am335x_boneblack_vboot_defconfig?

I use the setting as above to generate MLO and u-boot.img, but it seems the boot-up from SD card is fail. BBB connects to my windows laptop via USB cable. I just see the COM port is showed in my laptop and disappeared again repeatedly. I don’t know why? Does anyone have any suggestion? Thanks a lot.


For any u-boot work, you need a real usb-serial adapter plugged into
J1, to monitor u-boot booting, otherwise you'll just waste your own