TFP410: Digitizing screen signal

Franz Schellhase

Part Number: TFP410
Other Parts Discussed in Thread: SN65LVDS301, SN65LVDS314

Hi Team,

Can you have a look at the following customer challenge, please?

We would like to take the image data of a screen and compare it with a reference. We have only currently the problem to digitize this screen signal.

In principle we have only 2 interfaces (see "sketch") where we could tap the signal: Parallel 24-bit RGB888 or LVDS. During the research I stumbled over the TFP410 chip.
Here is the application report: www.ti.com/.../slla559.pdf
This could convert RGB888 to HDMI which we could then digitize via HDMI->USB. But we would prefer LVDS to HDMI, because we can reach this signal better.
The screen resolution is 240x800px.

Would you have an appropriate solution there, or perhaps a completely different approach to digitizing the image data? (At the end would be the desire to be able to tap the image data via Ethernet).
(The idea to put a camera in front of the display is also there, but this brings other problems that we would like to avoid).

Thank you,

Franz

over 3 years ago

0 David (ASIC) Liu over 3 years ago

TI__Guru**** 177676 points

Hi, Franz

For LVDS to HDMI, you can refer to this app note and see if the proposed solution works, https://www.ti.com/lit/an/slla559/slla559.pdf.

Thanks

David

0 Lars Ostheim over 3 years ago

Prodigy 20 points

Thank you for your answer.

We need some more specific support regarding compatibility.

The app note states: "The TFP410 supports pixel clock frequencies in the range of 25 MHz to 165 MHz".
Our pixelclock is "only" 12 Mhz which i think excludes the TFP410, am I right?

But are there any other solutions to get the image from the screen? (Especially in combination with the LVDS signal from a SN65LVDS301)

0 David (ASIC) Liu over 3 years ago in reply to Lars Ostheim

TI__Guru**** 177676 points

Hi,

Unfortunately we do not have a LVDS to HDMI solution that can support pixel clock in the range of 12MHz.

Thanks

David

0 Lars Ostheim over 3 years ago in reply to David (ASIC) Liu

Prodigy 20 points

Maybe anything from parallel RGB888 to something we can easily digitalize?
SN65LVDS301 -> SN65LVDS314 -> (here we are at RGB888) -> ...???...-> PC

0 Casey McCrea over 3 years ago in reply to Lars Ostheim

TI__Guru** 103215 points

Lars,

TFP410 can be used - you will just need to implement pixel repetition on the source to get above the minimum 25MHz PCLK which is actually the minimum PCLK rate from the HDMI standard itself.:

Best Regards,

Casey

0 Franz Schellhase over 3 years ago in reply to Casey McCrea

TI__Expert 3605 points

Hi Casey,

As discussed, can you clarify a bit more?

What IC do you suggest for implementing pixel repetition?
With pixel repetition the customer would need at least a factor of 3 to get above 25MHz (12MHz * 3 = MHz), correct?
Do you have an easy alternative suggestion for digitizing the 24 Bit RGB signal?

Thank you,

Franz

0 Casey McCrea over 3 years ago in reply to Franz Schellhase

TI__Guru** 103215 points

Hello Franz,

1. Pixel repetition is something that would be done in the source side that is generating the original video. It could also be done in an external path through FPGA or video ASIC/processor.

2. Yes

3. When you say "digitizing" do you mean putting the signal into DVI/HDMI interface? From the diagram you provided originally, it seemed like the video signal is already digital

Best Regards,

Casey

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TFP410: Digitizing screen signal