Tag Archives: backlight

Building the Intel EMGD display driver for Sony VAIO P with fully working backlight control


The Windows 7 driver for the GMA 500 GPU has not been updated for nearly two years now (v2030 from September 2010). According to this document Intel will only support and continue to maintain the EMGD driver going forward. This is a driver for Linux and Windows primarily for embedded systems, but unfortunately its target audience is system manufacturers and not end users (it’s distributed as a driver build kit). You need quite a detailed technical understanding of the hardware you’re creating the driver for, in particular the LCD panel specifications. Sony are unlikely to provide new driver builds for a three year old laptop, and it will most likely be needed for Windows 8 compatibility. I seem to remember reading that the Windows 8 Release Preview will not accept the GMA 500 Windows 7 driver. The EMGD driver does also have one big advantage in that it includes an OpenGL ICD, which the Windows 7 GMA 500 driver has always lacked.

Thanks in part to ‘viewtiful’ on the Pocketables forum having shared the DTD details for the 1600×768 panel, several people (myself included) had built prior versions of EMGD for the VAIO P, but no one was able to get the LCD backlight working correctly. The onscreen control provided by Sony Shared Library has 8 different levels, and it would turn off the backlight completely at levels 1-3. Experimenting with building new drivers is an extremely slow and painstaking process, especially when you’re not very clear on which values may need tweaking, but I’m pleased to say that I finally got all 8 brightness levels working this evening. And rather than keeping that knowledge secret, I’m sharing it here so that other Vaio users can build their own EMGD drivers for future release versions.


Here is my pre-built driver:


Download and install Intel EMGD (version 1.16 from November 2012 is the latest at the time of writing). Launch the emgd-ced shortcut it has created on your desktop. This will start the java builder application.

Firstly create a new DTD called 1600×768@60Hz with settings as shown. Don’t worry about the greyed out values at the bottom of the screenshot – they’re not used.


Next create a new configuration called 16x7Sony like so:


Define the LVDS port name as MID (the name the regular GMA 500 driver uses), select the options as shown, taking care to select the custom DTD you just created:


In that same screen, click the Attributes button and set the Inverter Frequency to 300. Many thanks to Kirk over at the Intel Embedded Communities Forum for helping me to home in on this being the crucial setting. There are several mentions in the EMGD documentation of a reference value of 20300 which turns out to be incorrect for the VAIO P’s screen. I spent hours searching high and low in vain for a datasheet for this LCD panel (a Toshiba LT080EE04000). Eventually I discovered on the Notebook Review forum that a user called jeonghun had created an EMGD 1.10 build crucially with all eight backlight levels working for the VAIO X laptop which also has a GMA 500, though with a different 1366×768 panel. Since at this point I knew what to look for I opened his driver inf and discovered the magic value of 300. I took a guess that the motherboard-to-LCD circuitry would probably be similar for both models of VAIO.


Click Finish to close that window, and now click on Flat Panel Settings. The VAIO P panel is an 18bit panel. I can’t remember exactly, but I think all these values are the defaults:


Now that we’re finished with the LVDS settings (the built-in screen), click Next to move on to configuring the sDVO external monitor connection. Name it Monitor to keep it consistent with the Windows 7 GMA 500 driver. We don’t need any customization other than what is shown in this screenshot:


The final screen after this relates to building a video BIOS which we aren’t interested in so leave these settings on the defaults. Once finished, create a new package called SonyVaioP:


Finally while selecting the package, click on Generate Installation in the toolbar. This will create your zipped driver which can be found in: