AnsweredAssumed Answered

AD9889B as DVI transmitter

Question asked by poluekt on Feb 20, 2011
Latest reply on Feb 23, 2011 by poluekt



I'm asking for some help or direction...


The problem, in general, is: the HDMI transmitter AD9889B does not toggle the TMDS lines. There is a constant voltage of ~2.6..2.8V on the lines.


The transmitter is not in power-down mode and senses the monitor:

Reg. 0x41 = 0x10;

Reg. 0x42 = 0xE0;


The initialization was performed accordingly to the "Quick Start Guide", on p. 11 of the AD9889B programming guide (Rev. A, October 2010).


AD9889 device implemented in our board must currently act as DVI transmitter, e.g. no audio, no encryption, no CSC (RGB24, 4:4:4) and connected to the standard PC monitor (LCD, 1280x1024) via standard DVI-D connection.


I could not find proper clarification in the AD9889B documents which PC standards does it support in DVI mode and made an assumption that DVI-compatible device will accept video stream accordingly to the VESA DMT standards (in my case: DMT ID = 23h, 1280x1024, 60Hz, pixel clk = 108MHz, syncs polarity = positive).

Is this assumption correct?


If not, where can I find a description of the DVI timings for Computer Monitors which are supported by AD9889B? (such as: 1024x768, 1280x1024, 1600x1200, etc.).


If the video stream timing is not the problem, I would very appreciate any advices and directions to find out why the transmitter remains idle...


Thank you very much in advance!


-- Andrey