Mark Roy

LVDS and VGA at the same time?

Discussion created by Mark Roy on Jan 19, 2012
Latest reply on Mar 13, 2012 by Mark Roy

Hey folks, 

I'm evaluating the i.mx53 for an embedded linux project but require duel lvds display.  Since the start board only makes available one of the two ldb outputs from the chip, I thought I would at least try and get LVDS and VGA at the same time.  


I've got LVDS working with a 10" SVGA panel by modifying the ldb driver which was fairly straight forward, but it took some effort to get the clocks working correctly.  It seemed that whenever I would boot, the ldb clock would be overwritten.  Later I discovered pll4 was being set by both the ldb driver and the tve driver. 


Anyways, so I got it working by disabling the tve when booting and then the LVDS panel works correctly.  However, both lvds and tve drivers require different clocks to display correctly, so I thought that maybe I coulld switch tve over to pll3.   I made the changes to the clock.c and tve.c and now when I boot up, I get an unstable image on my VGA display.   I also cant seem to get the LDB driver to work at the same time still.  Looking closer at clock.c I can see that many other peripherals are using pll3 so what I think may be happening is that these peripherals drivers are changing the pll3 which causes the display clock to change and thus disrupts the VGA output temporarily.  


Is this something I should even bother messing around with or is it not possible to have both TVE and LDB at the same time on the quick start board?  Maybe if I disable the other peripherals on pll3 (there are a lot of them!  csi0, csi1, hsi2, cspi, ieee_rtc, ssi1, ssi2, ssi_ext1, ssi_ext2 , esai, usb_phy). 


I'm also working on a simple adapter board that will take the parallel display output from the expansion connector and put it through an lvds transmitter chip for my second output.  In this case I was thinking I would try and configure the second LDB display on the imx53 and just grab the same data that it would see on the parallel for my lvds transmitter.  Should work right?


Suggestions or ideas would be appreciated.