Setting up a Serial Connection

Connect Peripherals

  1. Insert your microSD card into the card slot on top of the COM. Be sure it clicks securely into place.
  2. Connect any peripherals you wish to use. For most first time users, the following peripherals are highly recommended:
    • A powered USB hub on the expansion board's USB Host port or an unpowered USB hub on the expansion board's USB OTG port with a USB On-the-Go cable
      • A keyboard via the USB hub
      • A mouse via the USB hub
    • A LAN connection via the Ethernet port for Internet access
    • If supported by your expansion board, a DVI-D capable display via an HDMI to DVI-D cable

USB Peripherals and USB Ports

Many Gumstix expansion boards come with both USB Host ports and USB On-the-Go (OTG) ports. The USB Host port is used exlusively for connecting peripherals to the system, while the USB OTG port may be used to either connect peripherals via a USB OTG cable, or to connect the Gumstix system as a peripheral to a separate host.

USB Host ports and USB OTG ports differ in the USB data signaling rates and electrical current they offer:

  USB HostUSB On-the-Go
Current (mA) 500 100
Signaling Rate High-speed (HS) @ 480 Mbit/s
  • Low-speed (LS) @ 1.5 Mbit/s
  • Full-speed (FS) @ 12 Mbit/s
  • High-speed (HS) @ 480 Mbit/s

Many USB peripherals use a full-speed (FS) signalling rate, and will not work on the USB Host port, which is high-speed (HS) only. If you are experiencing issues connecting USB peripherals directly to the Gumstix system, connecting peripherals first to a powered USB hub and then connecting the powered hub to the Gumstix system will often solve the problem.

Establishing the Serial Connection

Select your development platform below for the appropriate instructions:

Connect from Linux

Establish a Serial Connection via the Console

  1. Connect your development machine to the expansion board's console port with a USB A to mini-B cable.
  2. You will need to determine the device name of the USB serial port using the following command:
    $ dmesg | grep tty
    Your Gumstix COM should be the last entry. E.g.,
    [ 0.000000] console [tty0] enabled
    [ 0.853593] serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
    [ 1.047979] 00:09: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
    [ 127.108578] usb 1-1.6: FTDI USB Serial Device converter now attached to ttyUSB0

    In this example, the serial connection to our Gumstix COM is on the device /dev/ttyUSB0.

  3. Use the following command to start a serial connection with your Gumstix COM:
    $ sudo screen <USB DEVICE NAME> 115200

    Where <USB DEVICE NAME> is the fully qualified path to the device name determined in the last step. E.g.,

    $ sudo screen /dev/ttyUSB0 115200

    If Screen is not installed, you can install it by typing:

    $ sudo apt-get install screen

Connect from Microsoft Windows

  1. First, plug in and power your Gumstix board (as above).
  2. Install the FTDI Virtual COM Port driver if you have not already done so.
  3. From Windows, you will need to find out which COM port on which your device will show.  To do so, open the device manager.  The fastest way to do this is via the Run dialog.  Press Start->Run from your desktop or press Winkey->R from your keyboard.  A small dialog box should pop up.  Type in devmgmt.msc and then press enter.


  4. Scroll through the device manager and expand the Ports section.  When plugged in, your Gumstix board should show up.  If unsure, you can unplug and replug the device.


  5. Next, download Putty from hereand run it.  Set Putty to connect via Serial and set the speed to 115200.  Make sure the COM port is set to exactly what you saw in the device manager.


  6. Click on Open to connect to your device.  You should now see a black box.  Restart your Gumstix device by pressing the reset button.  You should now see the bootup sequence.
  7. Log in as in the Kermit tutorial.

Connect with SSH or VNC

By default, it is possible to connect to Gumstix COMs using SSH or VNC.  Overo COMs will broadcast their presence on the mDNS; with the standard 'local' domain, you could connect to a single Overo on your local network via ssh:

$ ssh overo.local

COM modules run X11VNC to enable users to view the root desktop which is useful if you need remote graphical access to your computer.  Note that X11VNC will display the first X display (i.e. 0.0) where many other VNC programs will display a new X display (e.g. 10.0).


Boot Your System

  1. Connect the 5 Volt power supply to your expansion board.
  2. The LED indicators on the COM should illuminate blue and green. The boot process will display on your development machine's terminal.

    • If your expansion board is connected to its own monitor, you will not see the boot process until after the display drivers are loaded at a later stage.
    • If the blue and green LEDs on the COM do not illuminate and you see nothing in your terminal, try pressing the reset button on your expansion board until you see a boot process. If the problem persists, the image may not have been flashed successfully. You can try flashing it again, or try using a different image.
  3. Press any key when prompted to hit any key to stop autoboot.

    The typical boot process looks similar to the following:

    reading u-boot.img
    reading u-boot.img
    U-Boot 2012.04.01 (Jul 19 2012 - 17:31:34)
    OMAP36XX/37XX-GP ES1.2, CPU-OPP2, L3-165MHz, Max CPU Clock 1 Ghz
    Gumstix Overo board + LPDDR/NAND
    I2C:   ready
    DRAM:  512 MiB
    NAND:  512 MiB
    MMC:   OMAP SD/MMC: 0
    In:    serial
    Out:   serial
    Err:   serial
    Board revision: 1
    Direct connection on mmc2
    timed out in wait_for_pin: I2C_STAT=1000
    I2C read: I/O error
    Unrecognized expansion board
    Die ID #2d3800229ff8000001683b060a00b012
    Net:   smc911x-0
    Hit any key to stop autoboot:  0 
    Overo # 
  4. Das U-Boot bootloader comes with a default set of environment variables that may change as new versions are released. Users should clear their current set of environment variables the first time booting with a new version.

    This applies to systems with NAND flash only.

    At the U-Boot prompt, type the following commands:
    # nand erase 240000 20000
    # reset

    Verdex Pro users may need to change the U-Boot environment variables to specify that the kernel must be loaded from the microSD card. Use the following commands:

    # mmcinit
    # fatload mmc 0 a2000000 uimage
    # setenv bootargs console=ttyS0,115200n8 root=/dev/mmcblk0p2 rw rootdelay=1
    # saveenv
        Note: users need only add saveenv if they want to save this setup for future boots
    # bootm a2000000
  5. Users of Gumstix LCD panels with AltoPalo or Chestnut expansion boards only: Click here for some additional instructions on using your LCD panel.

    Additional Steps for Users of LCD Panels on Alto, Palo or Chestnut Expansion Boards

    To use one of the Gumstix LCD panels, you will need to modify Das U-Boot's default display variable to instruct the kernel to load the corresponding driver with the following steps:

    Alto users must be using the custom MLO and U-Boot binaries explained in step two.

    1. Interrupt the autoboot sequence by pressing any key at the following prompt:
      Hit any key to stop autoboot: 5
    2. Depending on the size of your LCD screen, you will need to type one of the following at the U-Boot prompt:
      Screen Size: 4.3" 3.5"
      setenv defaultdisplay lcd43
      setenv defaultdisplay lcd35
    3. You can save this setting for future boots with the following command:

      Saving environment variables only works on COMs with NAND flash. On COMs such as the Overo Tide COM and Overo Sand COM, which do not have NAND flash, creating persistent environment variables requires recompiling U-Boot's source code after altering include/configs/omap3_overo.h. See Accessing Source Code for more information.

    4. Finally, instruct U-Boot to continue with the boot process:

Your COM will now go through the boot process, ending at a Linux login prompt in the terminal similar to the following:

Linaro 12.11 overo tty1
overo login:

Enter the username root at the prompt and press Enter to login. There is no password on newly-flashed images. Users of Yocto Project images will not be able to login as root via the GUI due to an upstream Yocto Project bug.

The XFCE graphical login screen on Linaro-based images from Gumstix.

For users of Linaro images logging in via GUI: The username and password for this login are both gumstix.

Congratulations! Your Gumstix system is set up and ready to use.

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