Adding USB SVGA

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On XO-1.5 and using recent Operating Systems, it is easy to make a USB2VGA adapter work. Using USB2VGA adapters slows your XO down, and has some limitations (see below for details).

Selecting the right USB-SVGA adapter

This technique is supported with some USB-SVGA adapters based on the SIS USB-SVGA device, which uses the 'sisusbvga'(kernel) and 'sisusb'(xorg) drivers.

This driver supports cards based on the Net2280/SiS315 chipset, according to the author's page here. Some devices reported to work according to the NSLU2 wiki

Using lsusb, we have seen these identifiers on devices that work: 

 Bus 004 Device 005: ID 0711:0900 Magic Control Technology Corp. SVGA Adapter

Important notice : In older OSs, unless you compiled the sisusbvga module for your kernel, the module can possibly not be fully powered on, do not think the XO is not powerful enough to handle it, just insert the module to make sure it gets powered on.

On XO OS 10.1.3

Just plug the USB2VGA device to the XO, and start it up (or restart it if it is on). The desktop will only appear on the external display. The LCD of the XO will not be operational.

On XO OS 10.1.1 and 10.1.2

You will need to install some required modules from the main repositories 

yum install xorg-x11-drv-sisusb

And the RPM containing the required auto-configuration scripts 

wget http://dev.laptop.org/~martin/public_rpms/10.1.3/olpc-utils-1.0.31-1.fc11.i586.rpm

rpm -Uvh olpc-utils-1.0.31-1.fc11.i586.rpm

Connect the USB SVGA adapter, and restart your XO.

Notes

  • No mirroring, external display only. When you are using the USB VGA device, we disable the internal LCD screen. This is for two reasons
    • Performance is bad when trying to drive the 2 screen simultaneously. This is in part because the internal display is very differentrom a conventional screen.
    • On XO-1, the OS releases based on Fedora 11 (the 10.1.x series) cannot run both the internal video card and a SiS USB device.
  • Sometimes changes are not shown on screen immediately. Move the pointer to get the external display updated. There is a bug in the SiSUSBVGA driver that "forgets" to update the screen. We are investigating.

On XO OS 8.2.1 and earlier

The process is more complex as you will have to compile kernel and xorg modules. See Adding_USB_SVGA/Fedora_9_and_earlier

Limitations and quirks

  • When using the USB SVGA device, power saving mode is disabled so you battery will drain faster.
  • Performance is slower.
  • Sometimes, the image on the SVGA output will not be updated immediately. Moving the pointer (touchpad or mouse) a bit will fix it.
  • Minor screen corruption is sometimes visible.
  • Switching between VT (Text console) and X shows some minor screen corruption.
  • After a bit of inactivity, the SVGA port will "blank".
  • It does not interact well with sleep -- if you close the XO lid, and reopen, the behaviour might be buggy.
  • It does not constrain the mouse to the desktop area
  • Some activities (for example Pippy) do not work or display correctly on the "smaller" screen.
  • There may be a visible difference in color temperature
  • Some alternate keyboard glyphs are unreachable

Pictures

Here are some pictures of the OLPC working with the USB-SVGA adapter.

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Other Resources

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