Capturing coreboot console with FTDI FT2232H Mini Module
FT2232H Mini Module is a USB-to-serial/FIFO multipurpose development module. I will briefly show how to use it as a USB EHCI debug device to retrieve coreboot debug messages.
You need the module itself, a USB-UART converter, for example pl2303, a USB Mini-B-USB-A cable and 3 female-female jumper wires (and 3 more for pl2303, in my case).
With jumper wires, connect pins CN3-1 to CN3-3, CN2-3 to CN3-12 and CN2-5 to CN2-11.
Then attach USB-UART: pl2303's GND to CN2-6, pl2303's TXD to CN2-10 and pl2303's RXD to CN2-7.
The result should look something like:
(For detailed information on FT2232H pinouts, check out the FT2232H and FT2232H Mini Module datasheets.)
When the wiring is done, plug the USB cable into the debug port on a corebooted machine you want to get debug log from. Of course, coreboot has to be built with following options:
CONFIG_CONSOLE_USB=y CONFIG_USBDEBUG=y CONFIG_USBDEBUG_DONGLE_FTDI_FT232H=y CONFIG_USBDEBUG_DONGLE_FTDI_FT232H_BAUD=115200
Plug the USB-UART adapter (pl2303 in this example) into another computer and launch screen (or some other client of your choice):
# screen /dev/ttyUSB0 115200
Then power up the corebooted machine, and debug messages should appear.