All COM are delivered with pre-installed U‑Boot bootloader firmware. U‑Boot supports several low-level-debugging options and file download via Ethernet (TFTP), USB or via UART/serial X/Y/Z-Modem. These files can additionally be stored into the permanent flash-memory (NAND/eMMC) to be started by command or power-on.
Furthermore, the user can communicate with the bootloader via serial console, provided via RS232 using a Terminal Program.
For full documentation, incl. comprehensive command reference of U‑Boot please refer to: The U-Boot Documentation
To communicate with the CoM’s bootloader users need to connect to it via RS232 serial port, which dependent on the baseboard either is a D-SUB9 or pin-header (see Baseboard Pinouts, or TTL Debug UART pin header) connector, where the latter requires a TTL-2-USB RS232 converter.