DS90UB949-Q1: Not getting display 1280x768p connected to de-serialier with HDMI input given to serializer

Hello Chintha,

Are you linked to a remote deserializer device? You need to either have lock established or force a link through registers for this to work. Also are you using AC or DC coupled HDMI? Ensure that you have the proper VTERM voltage according to the datasheet. Finally, ensure that your video source can actually provide this somewhat uncommon resolution. In some cases the PC can identify that it is outputting the right resolution, but the timings coming out are actually not correct. I have seen this happen when trying to test non-standard custom resolutions with very obscure timings. 

Best Regards,

Casey 

Hi Casey,

Thank you for your reply. 

Yes. Our serializer is connected to deserializer remotely. We are able to generate test pattern from serialiser on the display connected to deserializer. we have measured 3.3V as VTERM.

As per your suggestion, I tested with standard resolution such as 1280x720 p. But still problem exists. Ensured that video source is providing mentioned resolution (1280x720p60). HDMI clock is detected as 75Mhz. 

I here by attaching Information and HDMI tab settings appeared on the ALP tool while giving HDMI input to serializer. One thing noticed is that, Serializer pixel clock is shown as 75.617Mhz where as deserializer pixel clock is shown as 71.304Mhz. Whether this difference in pixel clock is acceptable ? 

Also in HDMI tab, active video is shown as 0x0. Whether we are missing any register settings? Please help. Any hint will be greatly appreciated.

Regards,

Chintha

Hello Chintha,

Are you by chance using any sort of converter device here? For example Type-C to HDMI or DP to HDMI? Or is this a direct connection of the standard laptop HDMI port to the EVM? Also what shows up in the display settings for the laptop? Are you duplicating or extending the displays?

There are no register modifications needed to 949, so I really suspect the problem is with the source. 

By the way, the PCLK detect circuity in both sides is not meant to be highly accurate. It is normal to see a difference between source and sink reports. 

Best Regards,

Casey 

Hi Casey,

We are using direct connection from standard laptop HDMI port to serializer input. Display setting shows resolution of 1280x720p as per our EDID settings.

For the pattern generation, there are pattern generation registers to configure the LCD screen resolution but while giving the actual HDMI data we didn't see any registers apart from the EDID setting to specify the screen resolution. Our understanding is that we need to configure screen resolution only in the EDID while processing actual HDMI video, is this understanding correct? 

Regards,

Chintha

Hello Chintha,

Yes this is correct, you shouldn't need any additional configuration. I have done this many times before and have not seen this issue with our EVM where the detected resolution is 0x0 for one of the default EDIDs. Are you using the TI EVM or some other custom board?

Best Regards,
Casey