...and there was light

Beagleblog

Jul 02, 2009 GMT
Oliver Frommel

I got mail! Snail mail, that is. It's a package from Lyon in the south of France where Texas Instruments' DLP subsidiary is located (did you know that the DLP projector technology is owned by TI? see Wikipedia for more). Peeling away the packaging layer after layer I finally get to the actual package that contains the micro projector. After opening it I grab something small and black, but it's just the power supply. Finally I manage to find the projector which is really really tiny, about the size of a match box. Under a double bottom there's the requisite cable for attaching the DLP projector to the Beagleboard (it's HDMI to Mini-HDMI).

After connecting it to the board the first thing is to change the resolution to match the projectors maximum resolution, that is 640x480. I am doing that in the terminal program that is connected to the Beagleboard over a serial connection (see my older blog entry).
When you are trying to find the requisite boot options on the Internet you will find quite a lot of Howtos, many of them outdated. Some of them even suggest to update the boot loader or compile a kernel yourself.

Anyway, I was using the TI X-Loader 1.4.2 und U-Boot 2009.01-00013. Having updated the Angstrom distribution once I am also running a fairly recent kernel version 2.6.28. This is especially important because the format for specifying the screen resolution has changed during the course of kernel development (see this for more). The settings I have finally used successfully are the following, entered in the TI boot loader:

setenv bootargs console=ttyS2,115200n8 root=/dev/mmcblk0p2 rw rootwait omapfb.vram=2M,4M,4M omapfb.video_mode=640x480MR-24@60
saveenv

Even with some daylight from outside it's easy to read the characters on the projection screen. Even more so when the projected image is bright. With a distance of about one meter to the board the projection screen has a screen size of about one foot. I managed to get a bright projection with up to three meters but then the image becomes impossible to focus. This is not so easy anway because the small projector becomes so hot that you can barely touch it. The small size of the knob adds to that problem.

I probably shouldn't blame the micro DLP because after all it's a development device. It's still a good replacement for an LCD screen when you are on the road and have something to project on. It might even work for a movie night with your friends or family (both together might become difficult due to the limited screen size :).

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