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LVDS324 with IMX185 in long exposure mode

Edison Kang
Prodigy 80 points

If IMX185 exposure time is under  483ms, the output of LVDS324 is normal.

But if IMX185 exposure time is over 483ms, the output of LVDS324 is always 0x0FFF.

Do LVDS324 not support exposure time over 483ms?

  • 0
    TI__Mastermind 36085 points

    Hello Edison,

        Have you verified that the LVDS data is within the SN65LVDS324 bandwidth spec ( from 18.5MHz to 162MHz).

    Regards,

    Diego.

  • 0
    TI__Guru* 76130 points

    Hello Edison,

    What other parameters are affected when you change the exposure time (clk, bpp, etc) ?

    Please share what values you are writing to the LVDS324 CSR's.

    The LVDS324 only supports sony LVDS parallel at 60fps and with a clock of 74.25MHz, are you using 10-bit? 12-bit?

    Regards. 

  • 0 in reply to Elias Villegas M.
    Prodigy 80 points

    Hello ELIAS VILLEGAS,

    The value of Address 0x09~0x0E are 0x31, 0x62, 0x07, 0x80, 0x04, 0x38 .
    LVDS324 should be 1080p 60fs 12bits 74.25MHz.

    B.R.

  • 0 in reply to Edison Kang
    Prodigy 80 points

    If IMX185 is saturated, the maximum output value is 0xFFE not 0xFFF.

    The output of LVDS324 is 0xFFF only when the signal of IMX185 is blanking.

    When I set exposure time 500ms to IMX185, the VSYNC of IMX185 period is also 500ms.

    It means that the output of IMX185 is blanking almost 500ms.

    I guess that LVDS324 maximum detecting blanking time is under 500ms.

    If blanking time is over 500ms, the output of LVDS324 will become 0xFFF.

  • 0 in reply to Edison Kang
    TI__Guru* 76130 points

    Hello Edison,

    If the VSYNC period is 500ms that means that the frame rate is 2fps, with a resolution of 1920x1080 a 2fps rate will require a pixel clock of about 5MHz, the LVDS324 works only with a pixel clock of 18.5MHz to 162MHz, that will give you a minimum frame rate of about 10fps with that resolution.

    Regards.

  • 0 in reply to Elias Villegas M.
    Prodigy 80 points

    Hello ELIAS VILLEGAS,

    When VSYNC period is under 250ms, DM365 ISP always receive correct image data even if the frame rate is only 4fps. When IMX185 in long exposure mode, the output data is a very long V-blanking data with a 1080p image at the end. The clock of IMX185 is still 74.25MHz, LVDS324 receive data and HSYNC VSYNC of LVDS324 is correct. When V-blanking data VSYNC of LVD324 is driven high until the data is image then the VSYNC is driven low. DM365 ISP detect the VSYNC down trigger to skip V-blanking data receive the image data at the end. Only when exposure time is over then 500ms, DM365 ISP receive all 0x0FFF and that looks like blanking data.