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D3-3P-TDA3X-SK: YUV422 8-bit causes Buffer Error

Andrew Flowers
Prodigy 10 points
Part Number: D3-3P-TDA3X-SK
Other Parts Discussed in Thread: DS90UB953-Q1, DS90UB935-Q1

I'm attempting to display YUV-422 8-Bit CSI-2 video on the D3-3P-TDA3X over FPD-link III, vision SDK 3.06.   While the serializer (UB935) appears to be sending valid YUV-422/8-bit, the RX_PORT_STS2 Register (Address 0x4E) on the UB960 is reporting buffer errors.  According to the UB960, the line length on he video appears to be correct.  We are able to display RGB888 video (using the pattern generator) but not YUV-422/8 with the same hardware. 

What might cause the Buffer Error bit in the UB960 (reg 0x4E) to be set in the YUV422 case?

Thanks.

  • +1
    TI__Mastermind 18755 points

    Hello,

    The 960 buffers a few lines of video data while it waits for the CSI transmitter.  If there is an error then it means the buffer is overflowing and some CSI data is getting lost.  Need to look at the throughput capabilities of the 960 and verify you are not going over what the device is able to handle.

    Regards,

    Nick

  • 0 in reply to Nicholas Darash
    Prodigy 10 points

    Thanks, Nick.  We increased the CSI output speed (register 0x1F) from 800Mb to 1.6 Gb and were able resolve the buffer overflow and get frames through the system.  What I'm seeing now is CSI_LEN_ERR and checksum errors.  We're also getting half the frame rate on the output.

    Having to bump the output rate to >800Mb makes me suspicious that the input to the UB935 might be getting too much data and we're loosing data at the serializer.  This is CSI-2 4-lanes at 832Mb per lane.  Is that going to be too much for the 935?  We verified the CSI2 clock rate at the 935 as 832mbit/s (416 MHz clock) and that the 935 is operating in 4 lane mode. This is clearly greater than the stated maximum combined CSI2 data rate of the 935 (2.5gbps).

    Can TI please confirm that in 4 lane mode CSI2 data rate can not exceed approximately 625mbit/s per lane, regardless of the video blanking scheme.

     

  • +1 in reply to Andrew Flowers
    TI__Guru** 103215 points

    Andrew,

    DS90UB935-Q1 supports up to 632Mbps/lane over 4 lanes so this will not work. If you use DS90UB953-Q1 then it can support up to 832Mbps/lane but only if you have supplied the 960 REFCLK with 26MHz instead of 25MHz (so that the link is running at 4.16Gbps instead of 4Gbps) 

    Best Regards,

    Casey