my bricked tvbox into fel mode, Using linux-fexi tools, I tested my usb2ttl on my tvbox , without any output. I do not know why? Test command: https://github.com/linux-sunxi/sunxi-tools sunxi-fel -p write 0x4000 uart0-helloworld-sdboot.sunxi (succeed) sunxi-fel -p exec 0x4000 picocom -b 115200 /dev/ttyUSB0

armbian-config submenu STO001

My USB2TTL is tested on other tvbox such as Amlogic tvbox, works

Yeah, don't do that.. At least read "<application> --help" before doing sensitive stuff like that if you are unfamiliar. If that happened to you, and that is the reason you typed that.. For future reference: If you have a root account, you can change to root user with "su root" and enter passwd. You are then root and can add your user back to the groups needed. Or you can use the debian "child safe" way, "adduser <user> <group>" (only works on already existing users and groups) instead of usermod to begin with. But best is you learn usermod, since that will let you utilize that knowledge on pretty much any unix system.