Objective 2: Establish Serial Port Communication

You most definitely will want to load a custom Linux distribution onto a microSD card, and when booting from said card, you may encounter bugs especially if you will be modifying and boot arguments.  A good way to view the boot log is to set up a serial communication between your computer and the Beagleboard-xM.

1. Power down your Beagleboard-xM and connect a serial cable (If your computer has a serial port) or a USB to Serial adapter  between your computer and the Beagleboard-xM.
2. Open up a terminal and execute the command:

  sudo minicom -s


This will bring up the minicom program which will look something like:

  +-----[configuration]------+ 
  | Filenames and paths      | 
  | File transfer protocols  | 
  | Serial port setup        | 
  | Modem and dialing        | 
  | Screen and keyboard      | 
  | Save setup as dfl        | 
  | Save setup as..          | 
  | Exit                     | 
  | Exit from Minicom        | 
  +--------------------------+  



3. Select “Serial port setup” and a sub menu will come up with will look something like:

  +-----------------------------------------------------------------------+
  | A -    Serial Device      : /dev/tty8                                 |
  | B - Lockfile Location     : /var/lock                                 |
  | C -   Callin Program      :                                           |
  | D -  Callout Program      :                                           |
  | E -    Bps/Par/Bits       : 115200 8N1                                |
  | F - Hardware Flow Control : Yes                                       |
  | G - Software Flow Control : No                                        |
  |                                                                       |
  |    Change which setting?                                              |
  +-----------------------------------------------------------------------+
          | Screen and keyboard      |
          | Save setup as dfl        |
          | Save setup as..          |
          | Exit                     |
          | Exit from Minicom        |
          +--------------------------+



4. If you are using a serial port change the Serial Device to /dev/ttyS0.  If you are using a USB to Serial Adapter  change the Serial Device to /dev/ttyUSB0.  Ensure selection E is set to 115200 8N1 and change Hardware Flow Control to “No”.  After updating it will look something like:

  +-----------------------------------------------------------------------+ 
  | A -    Serial Device      : /dev/ttyUSB0                              |
  | B - Lockfile Location     : /var/lock                                 |
  | C -   Callin Program      :                                           | 
  | D -  Callout Program      :                                           |
  | E -    Bps/Par/Bits       : 115200 8N1                                | 
  | F - Hardware Flow Control : No                                        |
  | G - Software Flow Control : No                                        |
  |                                                                       | 
  |    Change which setting?                                              |
  +-----------------------------------------------------------------------+ 
          | Screen and keyboard      |
          | Save setup as dfl        |
          | Save setup as..          |
          | Exit                     |
          | Exit from Minicom        |
          +--------------------------+



5. Select “Save setup as dfl” to save these settings as the default and then select “Exit”.  The communication port will now open and the terminal will look something like:

  Welcome to minicom 2.5

  OPTIONS: I18n                                                               
  Compiled on May  2 2011, 00:39:27.                                          
  Port /dev/ttyUSB0                                                           
                                                                            
  Press CTRL-A Z for help on special keys 



6. Power on the Beagleboard-xM and the boot log will display on your computer's terminal.  It will look something like:

  Texas Instruments X-Loader 1.5.0 (Mar 27 2011 - 17:37:56)
  Beagle xM
  Reading boot sector
  Loading u-boot.bin from mmc


  U-Boot 2011.03-rc1-00000-g9a3cc57-dirty (Apr 01 2011 - 17:41:42)

  OMAP36XX/37XX-GP ES2.1, CPU-OPP2, L3-165MHz, Max CPU Clock 1 Ghz
  OMAP3 Beagle board + LPDDR/NAND
  I2C:   ready
  DRAM:  512 MiB
  NAND:  0 MiB                                                                   
  MMC:   OMAP SD/MMC: 0                                                          
  *** Warning - readenv() failed, using default environment                      
                                                                              
  In:    serial                                                                  
  Out:   serial                                                                  
  Err:   serial                                                                   
  Beagle xM Rev C                                                                
  No EEPROM on expansion board                                                   
  Die ID #765000229ff80000016849a90100f016                                       
  Hit any key to stop autoboot:  0



7. At this point you can hit any key on your computer's keyboard to stop the boot sequence if you want to add any on-the-fly modifications.
8. While using minicom, you can press Crtl+A to enter minicom commands.  To exit minicom press Ctrl+A followed by X.  Since we set the necessary minicom parameters as default, the next time you want to start minicom just use the command:

  sudo minicom

The configuration menu will not execute and it will start communication. 

How I learned this:

• http://elinux.org/BeagleBoardBeginners#Setting_up_serial_connection_between_your_desktop_machine_and_the_BeagleBoard
• http://www.ibm.com/developerworks/linux/library/l-beagle-board/