AD725 issues

We have an ongoing project which is using ivy bridge + QM77 platform + AD725. The system equipped with on TVOUT(NTSC) by extract analog signal from standard VGA output. Following picture is the result of display.

Unfortunately, I checked the datasheet as following description. It look like “noninterlaced” and “interlaced” mode is the first problem to me. How do I check and modify the “internal register” to make it work? Do you have any similar application or customer that are using the same platform?

Displaying VGA Output on a TV

The AD725 can be used to convert the analog RGB output from a personal computer’s VGA card to the NTSC or PAL television standards. To accomplish this it is important to understand that the AD725 requires interlaced RGB video and clock rates that are consistent with those required by the television standards.

In most computers the default output is a noninterlaced RGB signal at a frame rate higher than used by either NTSC or PAL. Most VGA controllers support a wide variety of output modes that are controlled by altering the contents of internal Registers  It is best to consult with the VGA controller manufacturer to determine the exact configuration required to provide an interlaced output at 60 Hz (50 Hz for PAL)

I saw there is a tool to make the resolution and display mode fit in the standard of NTSC from your website. Do you have any kind of the tools that can help me to test the functionality of AD725.

  • 0
    •  Analog Employees 
    on Aug 27, 2013 10:36 PM

    Hello,

    This part really can do no timing conversions of any kind, to be clear. I don't believe there is any current program that we could provide that woud do this but I'll check.

    Why not simply use an ADV7513 or ADV7511 and have a HDMI/DVI out to a TV instead of such a low resolution NTSC?

    Dave

  • 0
    •  Analog Employees 
    on Aug 29, 2013 8:33 PM

    Hi Hank,

    The TV.EXE program that is cited in the "Eval Board Instructions" is an old (20 years or so) DOS program that is not compatible with current Windows operating systems.  You will need an interlaced RGB source at a resolution that is scaled to match the composite output -- see page 14 of the data sheet for details.  As Dave indicated, the AD725 does not do any scaling -- its basic function is to do the matrix conversion of RGB to YUV and the chroma modulation.

    Best regards.

    --Jonathan

  • Dear Dave:

          Thanks for your reply. Actually, our platform is QM77. We need to have the TVOUT on our platform. So we are using VGA to NTSC encoder generating the output for our customer. Does Analog Devices have any customer they are using any chipset like us to meet the demand of old product? ADV7513 or ADV7511 are not suitable for us since the output must be NTSC. We already have three other different digitalize video ouptu at our platform. In the mean time, we was asking vendor of chipset how do we do the modification, too. Allow me to narrow down my question here, if we can get the solution of modifying register or VBIOS, AD725 is not suitable for us.

    Thanks.

  • 0
    •  Analog Employees 
    on Sep 6, 2013 6:05 PM

    Hello,

    The timing parameters of NTSC are a standard so it's a matter of understanding the details in programming your video card. This is not something we know about.

    Dave

  • 0
    •  Analog Employees 
    on Aug 2, 2018 2:27 PM
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin