Using framebuffer with AOC E1649FWU monitor on Ubuntu 14.04

[berryja]

I am trying to use an AOC E1649FWU monitor on a system running Ubuntu 14.04.3 LTS (64-bit). The monitor is recognized and after installing the latest DisplayLink drivers, the backlight comes on, but I cannot get anything to be displayed on the monitor. I am not running X on the system and would like to just use the framebuffer to display things on the monitor. I see that a framebuffer device is created /dev/fb1 (and sometimes /dev/fb2, it seems to always create a new device) but writing to it does not seem to do anything. The monitor just remains black with the backlight on.

Most people seem to be concerned with getting X to run, but I would rather avoid using X if I can. Anyone get a DisplayLink monitor working with the framebuffer?

[samjam]

I see from the spec sheet that this monitor has
Display Colours: 262K
well lower that the typical 16.7 million.

So I'm guessing it is an older DL-1x5 and DL-1x0 hardware (total guess).

If I am right, then try using udlfb instead of udl+evdi.

Right now I am typing this on LinuxMint 17.3 with an old USB adaptor and udlfb on an ESXi virtual machine on a DELL T320 server.

If I use udl, I get your problem - just a blank screen, and even the "fbi" program can show nothing on the monitor (although it thinks it is).

So try blacklisting evdi and udl, and modprobe udlfb and then see if the framebuffer works.

[berryja]

I am not sure what the hardware is exactly, but using the udlfb driver, I am able to get images to display using the fbi program. Interestingly, the display stays off (backlight off) until I display something on it. The first run seems to have some issues (black pixels show a random line pattern), but after I get all the pixels painted not-black, everything seems to work. The display comes up in 16-bit mode (5, 6, 5) which is not as convenient to work with, but I guess better than not working at all.

I have not gotten it to work with a custom app I wrote to draw on the framebuffer. I guess now it's just comparing to the fbi code to see what it is doing differently. I am not doing any VT stuff in my app, so maybe that is it.

Thanks for the suggestion.

[berryja]

I finally got it working using my custom code. After ripping apart the fbi app code, I figured out the trick was writing to the buffer twice with a little bit of time between.

[samjam]

I finally got it working using my custom code. After ripping apart the fbi app code, I figured out the trick was writing to the buffer twice with a little bit of time between.

That is very unexpected. You just write the image twice with a small delay?