Objective 4: Get the LVDS LCD Touchscreen to Display

The Beagleboard-xM provides an amazing amount of processing power and application flexibility in a tiny package. The small size of the Beagleboard-xM lends itself to small devices, many of which must display information to its users. Low power LVDS touchscreen displays are ideal for this type of application because of their low power consumption and scalable size. The following instructions use a 10” LVDS touchscreen display from Chalkboard Electronics.

1. With the Beagleboard-xM off, connect the touchscreen to the LVDS interface board using the LVDS cable and connect the LVDS interface board to the LCD Expansion headers on the bottom of the Beagleboard-xM.
2. Insert the microSD card that contains the console version of Angstrom (built in Objective 3 of the blog) into your computer and navigate to the boot partition.
3. In order to send video signals to the LVDS touchscreen, custom boot arguments must be sent to the U-Boot bootloader. U-Boot looks for these boot arguments in the “uEnv.txt” file. Using a text editor create a file called “uEnv.txt” with the following content:

mpurate=1000
dvimode="1280x800MR-16@60 omapfb.vram=0:8M,1:4M,2:4M"
vram=16M
optargs="consoleblank=0"
console="tty0 console=ttyS2,115200n8"


The display I am using provides a maximum resolution of 1280 by 800. The resolution set in the “dvimode” property must match the maximum resolution of the display. If they do not match, the display will remain black.

On a side note, there is a lot of information on the Internet that claims that the boot arguments are modified using a “boot.scr” script to create a “boot.txt” file in the boot partition. This was the correct approach for earlier versions of Angstrom but the display driver of the most recent stable release (2011.03) has changed so that now it searches for a “uEnv.txt” file for its boot arguments.


4. Save the “uEnv.txt” file to the boot partition of the microSD card.
5. Eject the card from your computer, insert it into the Beagleboard-xM and apply power to boot up. The boot log will appear on the LVDS screen followed by the Angstrom ASCII art and the console prompt. 

How I learned this:

• https://groups.google.com/forum/?fromgroups=#!topic/beagleboard/4E8_puIhrm8
• http://www.sakoman.com/OMAP/how-to-change-the-display-resolution.html