This section documents how to use the UART to load files to boot the board into U-Boot. After that the user is expected to know how they want to continue loading files. Booting U-Boot from the console UART

In some cases we support loading SPL and U-Boot over the console UART. You will need to use the spl/u-boot-spl.bin and u-boot.img files to boot. As per the TRM, the file is to be loaded via the X-MODEM protocol at 115200 baud 8 stop bits no parity (same as using it for console). SPL in turn expects to be sent u-boot.img at the same rate but via Y-MODEM. An example session from the host PC, assuming console is on ttyUSB0 and already configured would be and the lrzsz package is installed

$ sx -kb /path/to/u-boot-spl.bin < /dev/ttyUSB0 > /dev/ttyUSB0
$ sx -kb --ymodem /path/to/u-boot.img < /dev/ttyUSB0 > /dev/ttyUSB0