LCD to HDMI conversion

Jishor Emmanuel

Other Parts Discussed in Thread: AM3354

I am developing processor board based on AM3354 processor and i am planning to add a LCD to HDMI converter using TDA19988 chip similar to Beagle bone board.

But while referring to beagle bone board schematic , I have found that, it is using only LCD data 0:15 to interface with TDA19988 converter chip, why is it so,even TDA19988 chip could take whole 0:23 data lines?

Is there any reference design available using 0:23 data lines along with a TDA19988 chip?

Also please provide any linux drivers available for TDA19988 chip interface.

over 9 years ago

0 jelliott over 9 years ago

Expert 1510 points

Beaglebone only uses 16 of the 24 lcd data pins to keep pins open for other uses (The LCD capes work this way, too). The LSBs of the inputs to the TDA998x are grounded, and the 16 data pins are tied to the MSBs. You can easily pin mux out all 24 pins from AM335x and use them. Look at the GP EVM for an example of 24 pin usage.

All the drivers are in the kernel.

Here are the fbdev drivers: https://git.ti.com/ti-linux-kernel/ti-linux-kernel/blobs/ti-linux-3.12.y/drivers/video/da8xx-tda998x-hdmi.c

Here are the DRM drivers: https://git.ti.com/ti-linux-kernel/ti-linux-kernel/blobs/ti-linux-3.12.y/drivers/gpu/drm/i2c/tda998x_drv.c

If you don't know the difference between DRM and fbdev, look at the main SDK LCDC page: http://processors.wiki.ti.com/index.php/Sitara_SDK_Linux_LCDC

0 Jishor Emmanuel over 9 years ago in reply to jelliott

Prodigy 70 points

Hi Jelliott,

Thanks for the clarification,

While referring to the DRM and fbdev modes, i found that both are not supporting Hot plugging in HDMI.

Do you have any work around?

0 jelliott over 9 years ago in reply to Jishor Emmanuel

Expert 1510 points

Fbdev has no support for hotplug.

DRM has support for hotplug, but the driver for LCDC is not yet able to do hotplug. The LCDC Driver Guide from that wiki page I posted above has more details.

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LCD to HDMI conversion