Using Serial Debug Port on BeagleBone Black

It is interesting to see boot messages while the OS is coming up on BeagleBone Black. The messages are useful to debug any boot issues, for example, when bringing up a new device. This post gives step-by-step instructions to setup Serial Debug port of BeagleBone Black.

To get a handle on the things happening with the board, Serial Debug port on BBB comes very handy. With appropriate cable & software program on the host system, one can easily bring up a terminal that-

  • Shows the BBB boot progress
  • Allows you to login
  • Lets you do usual activity – editing, file system browsing, s/w installation etc. 

Hardware Required

FTDI USB-to-Serial cable

Software Required

Install your favorite terminal program on the host system. Screen, Putty for Linux based systems and Mini-com, Putty or similar for Windows based systems are some popular terminal programs.

Serial Cable Connection

Connect the serial end (6-pin all female jumper) of FTDI USB-to-Serial cable to BeagleBone Black as shown in the picture. Ensure Pin-1 (GND) is aligned to the white dot on J1 serial header.
Plug in the other end of USB-to-Serial cable to any free USB slot of the host system.

Terminal Program

The next step depends on whether you are using a Windows or Linux based PC to connect to BBB. I’m using two specific terminal programs, but the instructions should work for any other program as well.

Putty on Widows 7

After plugging in serial cable to Windows PC, open Control Panel\Hardware and Sound\Devices and Printers. Ensure this new device (USB <-> Serial Cable) is listed.
Right click to view device properties. Under Hardware, note down the COM* port name of USB Serial Port function (mine is COM3).
Open Putty. In session, select serial. Enter your COM* name, speed as 115200 and click Open .

Screen on Ubuntu

If you have connected USB-end of the serial cable to a Linux based system like Ubuntu, a new tty* device appears in the system. Note down its name. In my case, it was /dev/ttyUSB0. Open a term and issue below command-

 (Tip: Do ls /dev/ before and after connecting cable to find the new device name)

Now, the terminal (Putty or Screen) is waiting to receive data from serial debug port connected to BBB. Power ON the board and you should see bunch of OS messages showing boot progress and the login prompt.
Note that 115200 is the recommended baud-rate setting for the BBB. Below is the list of all settings. Often you will have to change only the baud-rate.
Baud  : 115200
Bits : 8
Parity : N
Stop Bits : 1
Handshake : None

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