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DS90UB947-Q1: Does DS90UB947-Q1 work with YUV data?

Victor Lee2
Prodigy 30 points
Part Number: DS90UB947-Q1
Other Parts Discussed in Thread: DS90UB940-Q1, DS90UB921-Q1

Hi, I am trying to convert the data out of Sony FCB-EV7520A camera to FPD-link 3 data using DS90UB947-Q1.

This chip uses an Open LDI standard, which I believe is compatible with the LVDS signals from the Sony camera.

However on the datasheet it shows a data structure that accepts 24 bit RGB pixel data, while the Sony camera outputs 16 bit YCbCr data stream, is this compatible?

If I pair DS90UB947-Q1 with DS90UB940-Q1 (de-serializer) to interface with MIPI CSI-2, am I going to get error or lose resolution?

Thank you,

Victor

  • 0
    TI__Guru** 103215 points

    Hello Victor,

    In the 947 datasheet you can find bit mapping diagrams for the OpenLDI signal to RGB888. Those can be compared to the corresponding diagrams starting on page 58 of the FCB-EV7520A data manual to see which bits map to which R/G/B bits in the 24 bit color space that 947/940 use. 

    However it's unclear to me if the FCB-EV7520A convention for sending HSYNC/VSYNC/DE signals on the D2 is the same as 947. Actually looking further in the document it does not appear that FCB-EV7520A follows standard bit positions for HSYNC/VSYNC/DE signals since the signal mappings provided for THC63LVD1024 as an example show these signals mapping to R/G/B data bits and R/G/B data bits mapping to HSYNC/VSYNC/DE (basically the ordering is swapped around). 

    This would be an issue specifically for connection with 940 because 940 uses the HSYNC/VSYNC/DE signals in order to determine packet boundaries - i.e. when to generate Frame Start, Frame End, Line Start, or Line End as part of the MIPI CSI-2 standard. So unfortunately I don't think this is a viable solution unless you have a way to remap so that the OpenLDI bit mapping going into 947 matches what is the in 947 datasheet - especially for the sync signals. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 30 points

    Hi Casey,

    Thanks for looking into this. I agree that the color mapping/Sync signals on the Sony camera appear to be different, not well explained in the manual.

    In fact all I am trying to do is to convert LVDS signals to a CSI-2 compatible format, would you have any solutions for parallel RGB/YUV to CSI-2 conversion?

    Thank you,

    Victor

  • 0 in reply to Victor Lee2
    TI__Guru** 103215 points

    Hey Victor,

    The solutions we have for this are DS90UB925-Q1 (85MHz PCLK max) or DS90UB921-Q1 (96MHz PCLK max). Those can take in parallel RGB and the you can connect the 92x to 940 and 940 will perform the CSI-2 conversion. 

    The only hard requirements are the maximum PCLK (<96MHz) and that the sync signal must be correctly provided (HSYNC, VSYNC, DE). Those are critical specifically for CSI-2 because they are used to define the data packet boundaries. Since CSI-2 is a packetized format it needs to know when to generate line start, line end, frame start, and frame end packets based on the sync signals. 

    So this could turn out to be quite a complex multi-chip solution: FCB-EV7520A -> LVDS to RGB converter -> 921 -> 940 -> CSI-2 

    The more practical option may be to use an FPGA or video processor for such a solution to avoid the need for so many steps. 

    Best Regards,

    Casey 

  • 0 in reply to Casey McCrea
    Prodigy 30 points

    Thanks Casey, that's very helpful. We are looking at other potential solutions at the same time, it seems TI doesn't provide a 1-2 chip solution for this problem.

    Regards,

    Victor