Using HDMI with the Toshiba AC100

1. Introduction

With the latest Kernel from jak, HDMI works on Ubuntu with the Toshiba AC100. The displays could be configured through “xrandr”. This article quickly describes how to use “xrandr” to setup different display modes.

Note: If you boot with the HDMI monitor connected, your desktop will be displayed on both, the AC100 screen and the HDMI screen. It is most likely, that the AC100 screen (since it has a smaller resolution) only shows the top left part of what is shown on the HDMI display. If you connect your HDMI display later on, it stays black. Both issues could be “fixed” with “xrandr”.

2. Check your Screen Capabilities

Connect your HDMI screen, and type on the command line:

xrandr

This lists all detected screens with their capabilities. E.g.:

Screen 0: minimum 256 x 128, current 1280 x 1024, maximum 2048 x 2048
LVDS-1 connected (normal left inverted right x axis y axis)
   1024x600       51.6 +
HDMI-1 connected (normal left inverted right x axis y axis)
   1280x1024      60.0
   1024x768       60.0
   800x600        60.3
   640x480        59.9     59.9

LVDS-1 is the build in screen, HDMI-1 the external one. Also note the first line stating ” maximum 2048 x 2048″. This means, the total screen size in with+height for both screens together must not exceed 2048×2048.

3. Configuring Dual Head with a Left/Right Screen

To get a desktop over both screens, use this command (makes the AC100 the left, and the HDMI the right screen):

xrandr --output LVDS-1 --mode 1024x600 --output HDMI-1 --mode 1024x768 --right-of LVDS-1

Note, that the following will not work (since it exceeds the above mentioned screen limits):

xrandr  --output LVDS-1 --mode 1024x600 --output HDMI-1 --mode 1280x1024 --right-of LVDS-1

Gives you an error like this:

xrandr: screen cannot be larger than 2048x2048 (desired size 2304x1024)

4. Only use the HDMI Display

To use the HDMI display, and switch the AC100 display off, use:

xrandr --output LVDS-1 --off --output HDMI-1 --mode 1280x1024

To revert this use:

xrandr --output HDMI-1 --off --output LVDS-1 --mode 1024x600