There is a dedicated header (J1) for getting to the UART0 pins and connecting a debug cable. Five additional serial ports are brought to the expansion headers P8 and P9, but one of them only has a single direction brought to the headers.

Two point five ways to access the serial console on your Beaglebone Black

$ sudo su -
$ echo BB-UART1 > $SLOTS # /sys/devices/bone_capemgr.9/slots
$ echo BB-UART2 > $SLOTS
$ ...

TODO: Enable at startup

    |  RX	| TX	| CTS	| RTS	| Device	| Remark

------- | ----- | ----- | ----- | ----- | ------------- | ------------ UART0 | J1_4 | J1_5 | | | /dev/ttyO0 | BeagleBone Black only UART1 | P9_26 | P9_24 | P9_20 | P9_19 | /dev/ttyO1 | UART2 | P9_22 | P9_21 | P8_37 | P8_38 | /dev/ttyO2 | UART3 | | P9_42 | P8_36 | P8_34 | /dev/ttyO3 | TX only UART4 | P9_11 | P9_13 | P8_35 | P8_33 | /dev/ttyO4 |
UART5 | P8_38 | P8_37 | P8_31 | P8_32 | /dev/ttyO5 |

Port settings

• Debug Cables
• Terminal Shells

Using a FTDI cable on Mac OSX, you can connect using:

screen /dev/tty.usbserial-AFWR836M 115200 8n1
# or
minicom -D /dev/tty.usbserial-AFWR836M -b 115200

To exit screen, you can either detach using Ctrl-a Ctrl-d and resume using screen -r or kill the window using Ctrl-a Ctrl-k

Screen command reference

stty -F /dev/ttyO1 9600

stty -F /dev/ttyO1 -a

from: https://groups.google.com/forum/#!topic/beagleboard/p8oEVlENq44 Instructions like http://www.armhf.com/beaglebone-black-serial-uart-device-tree-overlays-for-ubuntu-and-debian-wheezy-tty01-tty02-tty04-tty05-dtbo-files/ will help you enable one of the other serial ports after boot. You'll want to modify the default am335x-bone.dts to enable the ttyO4 at boot and add console=ttyO4 to the uenv.txt, so that you'll start seeing kernel output. I suggest you get to that point before trying to patch u-boot to use a different default serial port.

• Serial UART Header Pins
• BeagleBone Black Serial UART Device Tree Overlays for Ubuntu and Debian Wheezy (tty01, tty02, tty04, tty05 .dtbo files)
• Serial tty Device Tree Overlays (scroll down)
• Serial over USB
• Enable serial/UART/tty on BeagleBone Black
• BeagleBone Black Serial Debug Connection
• Flyswatter2 BeagleBone Black How To
• BeagleBone Black JTAG Adapter Kit
• Enabling ttyO1 on BeagleBone