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DS90UB940-Q1: data format question

Jimmy Gong
Expert 3600 points
Part Number: DS90UB940-Q1

Hi team,

Can we give RGB data to UB681, use UB940 to receive data through FPD LINK III, and then convert the data to 8bit YUV422 data for output through UB940?

BR,

Jimmy

  • 0
    TI__Mastermind 18046 points

    Hi Jimmy, 

    The 940 can output data in 8bit YUV422. However with RBG input, the 681 will not be the right serializer as it supports MIPI-DSI input data. 

    For a FPD-Link III solution set that supports RGB input and output 8bit YUV422, I recommend the DS90UB947 paired with the DS90UB940. 

    Best,

    Shu\

  • 0 in reply to Shu Huang
    TI__Expert 3600 points

    Hi Shu,

    you are right, the customer is using RGB888 which is the data type for MIPI-DSI. but i have no idea that why you said 681 will not be the right serializer since I saw the datasheet said 681 can support RGB888.

     

    In addition. There is a crop function written in the datasheet of UB681. Can such a picture size be cropped? Input 1280*720 and output 320*320.

    ...

    BR,

    Jimmy

  • 0 in reply to Jimmy Gong
    TI__Mastermind 18046 points

    Hi Jimmy, 

    Thanks for the clarification. I made the assumption that you were referring to non-packetized RGB video via LVDS input. If the customer SoC supports and outputs DSI RGB then the 681 and 940 pairing in FPD3 mode will work. 

    However, the 320*320 output resolution is too small as the 681 cropping function can only support resolutions that have a minimum VP PCLK of 25MHz when operating in FPD3 mode. 

    Best,

    Shu

  • 0 in reply to Shu Huang
    TI__Expert 3600 points

    Hi Shu,

    As you said 320*320 output resolution is too small as the 681 cropping function can only support resolutions that have a minimum VP PCLK of 25MHz when operating in FPD3 mode. I don't know the correlation between 320*320 output resolution and PCLK 25MHz. Why you know 25MHz's PLCK can't support 320*320 output? if PLCK is using 25MHz, how can we know the size of output resolution?

    BR,

    Jimmy

  • 0 in reply to Jimmy Gong
    TI__Expert 3600 points

    Hi Shu,

    In addition, customer saw CSICFG1 Register's IFMT can program the input data in HDMI by RGB444.

    They would like to ask

    1. When UB681 inputs RGB888, can UB940 normally receive and process RGB888 data and convert it to YUV422?

    2. Is there any successful case under this configuration? since customer is worried that data distortion will occur abnormal color imaging of the screen.

    BR,

    Jimmy

  • 0 in reply to Jimmy Gong
    TI__Mastermind 18046 points

    Hi Jimmy, 

    The VP PCLK is determined by Htotal * Vtotal * fps(refresh rate). Since I only have the active video resolutions, I did the below calculations:


    320 (Hactive) * 320 *Vactive) * 1.10 (10% video blanking) * 60Hz = ~6.75MHz which is way too low. 

    The original 1280*720 input (~60.8MHz) will meet the 25MHz minimum if uncropped. 

    RGB888 format refers to the bits per pixel of each color data. However, in HDMI terminology, RGB444 actually refers to the YCrCb subsampling which can still be RGB888.

    If you refer to the below table in the 940 datasheet, CSICFG1 register bits [3:2] = 00 still indicates RGB888 input in bit depth terms. 

    Best,

    Shu

  • 0 in reply to Shu Huang
    TI__Expert 3600 points

    Hi Shu,

    thanks for your detail explanation! I may need your help if customer have more question.

    BR,

    Jimmy