AnsweredAssumed Answered

7842 Auto Mode for Non Standard Resolutions

Question asked by nabs on Aug 28, 2011
Latest reply on Sep 1, 2011 by DaveD

Hi

 

This topic has been discussed many times but I am not sure there was any clear answer to it.

 

Using ADV7842. Have a VGA input which should be able to support 1920x1080p resolution. I go in Auto Graphics mode and configure three registers:

 

PLL_DIV_RATIO

CH1_FR_LL

CP_LCOUNT_MAX

 

I get a video but the image is shifted left. I looked at the scripts that came with 7842 and in the script, they are adjusting DE_START and DE_END. DE_START is set to 0x320 and DE_END is set to 0x3ED.  Start HS and End HS is still set to 0. What I dont understand is how are we setting these values. Why is DE_START shifted left -224 Pixels. Is there any algorithm to calulate these values, eg based onHysnc Width, Blanking Time, Front Porch and Back Porch?

 

Same case for 1280x720p. I really dont want to go down a path of creating tables for every non supported resolution and have custom values for DE_START, START HS and START VBI. I would rather calculate these values based on the timing information I already have like Hsync Width and H Blanking time. If ther are any known default length of DE (x number of pixels) or Hsync, then I will know exactly how many pixels to shift left or right. But if I dont know then I will have to have a huge data base made spicifically for 7842.

 

Nabeel

 

 

 

Outcomes