RGB(analog) question on the OMAP3730

Jack Chiu

Hi everyone:

I have a question about RGB(analog) on the OMAP3730.

In the design, we choose the CHIP "ADV7125" .

It use for convert Digital to analog signal.

When i study the SPEC, i found the chip only convert Red,Green,Blue signals.

And , the HSYNC & VSYNC is direct form OMAP3730's output (HSYNC&VSYNC)

Now, i contact the LCD Displayer, but something happend.

follow those picture: (the display is 1280*800@60)

you will see inside the red circle.

it's like some noise? Has anyone as same as problem?

How can i soultion the problem without change the chip?

Thanks a lot.

0 Steve Clynes over 14 years ago

Are you using the high speed DSS output pins?

The normal DSS output pins are only rated to 65MHz.

For the resolution you are using you need 75MHz, hence need to use the alternate DSS output pins.

BR,

Steve

0 Jack Chiu over 14 years ago in reply to Steve Clynes

hi, Steve:

Thanks for your response again.

we are already switch to the high speed DSS output, but it still has same problem.

so, will you have any idea about the problem resolution?

like a other attention in the S/W or H/W ?

BR,

Jack.

0 Steve Clynes over 14 years ago in reply to Jack Chiu

Try inverting the output pixel clock. It is possibly a set-up/hold violation problem.

This can be done with register DISPC_POL_FREQ (0x4805 046C) bit 14 (IPC)

BR,Steve

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