Troubleshoot DragonBoard Boot

You may have a scenario where you cannot boot the OS and see the display via HDMI. This section will give some alternative ways to troubleshoot this situation.

Monitor Compatibility

It is possible that the monitor you are using does not work with the HDMI output from this board. This is because you need to use a monitor that natively "speaks" HDMI. Even though you are using an HDMI to DVI cable, the GUI will only display on a monitor that can natively display HDMI output.

Many of the labs in the CSE building have monitors that do not use HDMI. Make sure to try using your board with a monitor that has a physical HDMI input. The instructors have monitors that use HDMI available at office hours.

Serial Debugging

If all else fails, you will need to borrow a serial cable and debug the situation. This subsection will explain how to connect the serial cable and read the serial data during boot up.

Make sure the µUSB and the jumper are removed so the board doesn't boot into fastboot. Plug your USB to serial cable into the serial header on the board (next to power).

Four our RS232 cable, the black wire is for pin 1 on the header. The connector is not the right size so it will barely go down at all on the pins. DO NOT FORCE THE CONNECTOR DOWN!

On your computer, run lsusb to make sure a serial device came up. You should see someting like:

Bus 002 Device 003: ID 067b:2303 Prolific Technology, Inc. PL2303 Serial Port

We need a terminal emulator to talk to the device over serial. We will use picocom for this. To install it on your computer, type:

sudo apt-get install picocom

The device may come up as either ttyUSB or ttyACM. Run ls /dev/tty* to check.

Now we'll connect to the device. Run:

sudo picocom -b 115200 /dev/ttyUSB0

replacing /dev/ttyUSB0 with the correct device port from the previous step. The -b flag sets the baud rate.

You will see output from the USB to Serial device that looks like this:

picocom v1.7

port is        : /dev/ttyUSB0
flowcontrol    : none
baudrate is    : 115200
parity is      : none
databits are   : 8
escape is      : C-a
local echo is  : no
noinit is      : no
noreset is     : no
nolock is      : no
send_cmd is    : sz -vv
receive_cmd is : rz -vv
imap is        : 
omap is        : 
emap is        : crcrlf,delbs,

Terminal ready

Once you have powered on the board, you will see serial output at this terminal. When the board boots up, you will see many kernel messages displayed.

Eventually it will display root@linaro-gnome:~#. If you don't see this, hit return and this prompt will show up.

Once you see the root prompt, you have a working serial connection to the board and the board is logged in as root.

Note: When booting the DragonBoard, you may have a scenario where you cannot see the keys on screen as you type. This is a serial timing issue of some sort. Type exit and then enter and you should get keys echoed.