Single Channel LVDS Display with 1920x1080@60Hz

[schulerstephan]

Hello Community,

I want to use a LVDS display with a resolution of 1920x1080 Pixel @60Hz (Dotclock = 148.5 MHz). The display has only a single LVDS Channel with 4 differntial data lines.

I think the limitation is the serializer clock of the LDB which must not be higher than 595 MHz. When I calculate the clock for my display (148.5 MHz Dotclock * 7 Databit = 1039.5 MHz Serializer Clock) this will not work.

Is this up to this point correct?

The solution now is to use the SPLIT mode. But then I have to use both LVDS channels of the i.MX6. One for the ODD data and one for the EVEN data. I have then a SerialzerClock of 519.75MHz, which is lower than the 595 MHz. But than I need an other display that supports the two LVDS channels.

Is this up to this point correct?

The last question is now: Where can I find the information which LVDS channel is responsible for the ODD data and which one for the EVEN data?

Thanks in advance,

Stephan

[sebastiannowack]

Hallo Stephan

I had similar problemes with the same display (I guess).

I build an android with the sabrelite BSP and changed my parameters

     described in:  https://community.freescale.com/docs/DOC-93617

After I set a frequency lower than 148.5 M pixel / s, I got a running system with a flickering screen. ( pixclock approx. 9000 )

Later I changed an entry kernel_imx/arch/arck/mach-mx6/ckolck.c in function int __init mx6_clocks_init(. . .)

     clk_set_parent(&ldb_di0_clk, &pll2_pfd_352M);

to:

     clk_set_parent(&ldb_di0_clk, &pll5_video_main_clk);

To exclude a conflict while initialising I switched off some entrys in init.rc:

I found, that android boots without the console:

#service console /system/bin/sh

#    class core

#    console

#    user root

#    group root

The system didn't flicker any more, but it became so instable, that a mouse movement turned the screen to black for a second.

I am new in building android, so I don't know if that means, you can reach higher values, than described in the imx6q-specs.

So I think you're right, and the 595 MHz is the maximum for single channel lvds.  I was irritated  by some other entries in the datasheets of imx and/or sabrelite.

Thanks,

Sebastian

[alfred_liu]

Hi,Stephan

the attached LCD is a dual LVDS panel, Maybe you can refer to.

[EgleTeam]

Stephan,

please pay attention on page 482 of the reference manual (dual-quad): max. frequency for single channel is 85mhz, so it is not possible to achieve 1920x1080@60.

Regards,

Manuel.

[schulerstephan]

Hi Manuel,

thanks! The 85MHz Pixelclock are exactly the maximum serializer clock (85MHz * 7 Bit = 595 MHz). That will confirm my calculation! :smileyhappy:

Regards,

Stephan

[alfred_liu · Accepted solution]

Hi, Stephan

1, yes, your caculation is exactly correct, signle LVDS cannot reach 1920*1080/60Hz, we need two LVDS port to support this.

2, I believe the ODD data and EVEN data are configured in our i.mx side, you can refer to our BSP reference code to get it.

[schulerstephan]

Hi Weisong Liu,

thanks for you answer!

I have to check the configuration for odd an even with my colleagues. Maybe I will come back later to this point.

To solve the hardware point I think there are two possible solutions:

1. We have to change the display to a dual channel LVDS type

2. We will use the parallel RGB interface which supports a pixelclock up to 264 MHz (single port) and then we have to use a external LVDS seralizer that support a higher bitrate.

Are there any other thinks to regard relating to the parallel RGB interface with a FullHD resolution? For lower resolutions this works fine for us!

Regards,

Stephan

[alfred_liu]

Hi, Stephan

you really undersatand our RM document deeply.

there is indeed two way to meet your requirement.

while I recommend you use two LVDS port to do this.

because I don't think 148.5MHz dotclock is a good thing for us( jitter, PCB layout, EMI.......).

[schulerstephan]

Hi Weisong Liu,

i am completely with you!

Furthermore I couldn't find a RGB to LVDS bridge which supports the 148 MHz.

Many Thanks for your help!

Regards,

Stephan

[EgleTeam]

TI has few transmitters for >150Mhz. Unfortunately those work at 1.8V: almost sure due the arguments that said Weisong.

Thanks,

Manuel.

[EgleTeam]

Stephan,

In our modules we only did the fanout of one channel. Sounds interesting to use a LVDS serializer from RGB.

Thanks!

Manuel.