Thread: [ANNOUNCE] Proof of Concept for extrenal screen display (USB VGA)
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Graham Cobb is offline Graham Cobb
2008-04-26 , 10:10
Posts: 162 | Thanked: 351 times | Joined on Apr 2006 @ Cotswolds, UK
#3
IMPORTANT: The instructions for using the proof-of-concept release of xsisusb are now at: http://xsisusb.garage.maemo.org/. The instructions given below are out of date and should no longer be used. They are left here just so that the flow of the thread make sense.

NOTE: This release has hardly been tested and has a number of restrictions. It is mainly intended for developers and is only really usable if you are comfortable using the Linux command line.
  • Hardware requirements and connectivity
  • Installing the software
  • Linux kernel driver
  • Image display
  • X-server

Hardware requirements and connectivity

The software requires an external VGA adapter attached using USB 2.0 and using a SiS USB VGA chipset. The adapter I am using is made by StarTech.com and is called "USB 2.0 to VGA Display Adaptor USB2VGA2". There are other adapters available and it would be useful if people could reply here if they can report success using any other adapter.

The adapter needs to be connected to the tablet, with the tablet operating in USB host mode (a powered hub will be needed). There is information on how to set that up for the N810 in this thread.

My configuration uses: the Nokia-supplied USB cable, a USB-A to USB-A gender changer, the standard A-to-B cable for my hub, the powered hub, the USB2VGA2 USB cable. I turn on USB host mode using:

Code:
echo host >/sys/devices/platform/musb_hdrc/mode
Installing the software

The software is currently hosted in my experimental repository: http://www.cobb.uk.net/NokiaIT/experimental.html.

To install the software, add a new Application Catalogue to the Application Manager with the following details:
  • Catalogue name: Graham's experimental repository
  • Web address: http://www.cobb.uk.net/apt/
  • Distribution: chinook
  • Components: experimental
  • Disabled: X

I recommend you keep this repository disabled except when you are actually installing stuff from it (nothing in that repository is normally expected to work!).

To install the software, enable the repository and install the following packages: sisusbvga-2.6.21, sisbit, xsisusb. Then disable the repository again.

Linux kernel driver

The kernel driver is installed as /lib/modules/2.6.21-omap1/sisusbvga.ko.

First, plug in the USB device (and enable USB host mode if you have not done that yet). Check using dmesg that the device has been seen by the kernel.

To start the driver, issue the following commands as root:

Code:
insmod /lib/modules/2.6.21-omap1/sisusbvga.ko
chmod 777 /dev/sisusbvga0
Check, using dmesg, that the driver has configured the device.

Image display

Static images can be displayed on the external screen using the sisbit program. At the moment, sisbit only supports images in the PPM format. A sample image is installed in /usr/share/sisbit/test.ppm.

This program can be run by the user, it does not need to run as root.

Code:
sisbit [-m mode] [-b bytesperpixel] [-s sisusbdevice] ppmfile
 where m=0,1,2,3 for 640x480, 800x600, 1024x768, 1280x1024
 and b=2 or 4 bytes per pixel
X-server

The X server is an integrated, non-configurable server, based on kdrive, just like the Nokia-supplied Xomap server. It is installed as /usr/sbin/Xsisusb and it can be run by the user, it does not need to run as root.

This server has null drivers for keyboard and mouse: no input or pointer events happen. It should be possible to send keyboard and mouse events using something like x11vnc (although it doesn't seem to work at the moment).

To see the list of options, use:

Code:
Xsisusb -help
I normally run the server with the following command line:

Code:
Xsisusb :1 -ac -screen 1024x768x24/32 -noreset
  • :1 -- this is the X display to use. Note that the normal screen is using display :0 so it is necessary to specify a different display.
  • -ac -- this turns off all access control (security) so anyone who has TCP/IP connectivity to the tablet can create windows on the external screen.
  • -screen 1024x768x24/32 -- this specifies the display mode to use. The following values are allowed: 640x480x16/16, 640x480x24/32, 800x600x16/16, 800x600x24/32, 1024x768x16/16, 1024x768x24/32, 1280x1024x16/16, 1280x1024x24/32.
  • -noreset -- do not reset the X-server when there are no clients left. This is because I typically do not run a window manager.

There are no ordinary X-windows programs available on the Internet Tablet, as far as I am aware, so to display something on the screen you need to use a remote system. The following command line will display a clock at the bottom right hand corner of the screen:

Code:
xclock -display 192.168.1.247:1 -update 10 -hands red -geometry 164x164-0-0 -norender
192.168.1.247 must be replaced with the IP address (or hostname) of the Internet Tablet.

Note: the Xsisusb server currently displays a . whenever a screen update occurs (it then copies the whole framebuffer to the device). This is to help me judge whether too many updates may be happening.
Last edited by Graham Cobb; 2008-05-01 at 11:57. Reason: Mark as obsolete
 

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