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ADV7343 Test Pattern Issue

Hi All, We're using ADV7343 video encoder to convert 24bit RGB video to a single ended CVBS signal. For testing first we generated the test patterns as per the data sheet by successfully writing I2C data. But the LCD display at the other end does not have a sign of the video signal (nor for 24bit RGB signal). I'm pretty sure that the I2C writing and register settings are okay, specifically the following addresses loaded with the bold color values :

0x17 --> 0x02

0x00 --> 0xFC

0x82 --> 0xC9

0x84 --> 0x40

The retrieved CVBS signal from DAC4 (low drive) for the test pattern is shown below :

And the schematic we use is attached herewith. A 27MHz of clock signal is fed to the CLKIN_A of the encoder !

What could cause this issue ? I read somewhere that a termination resistor has been used to workaround a similar issue. Any suggestions would be appreciated !

Thanks in Advance


PS: More to this, I checked a BOSCAM with the same LCD (that's SEETEC) through CVBS. The screen displays the camera input without any issue. 

  • Dear Jey,

    Hi, I found out that the issue was in the clock generation and I was able to detect the SD color bars after resolving it. Now after feeding the RGB signals from the host device, I am receiving a CVBS signal like below :


    So here, the color burst can be seen, but no color levels. Does this mean the RGB signals are not available at all ? This is my i2c writings :

    0x2B 0x17 0x02 Software reset.
    0x2B 0x00 0xFC All DACs enabled. PLL enabled (16×).
    0x2B 0x01 0x00 SD input mode.
    0x2B 0x02 0x10 RGB output enabled. RGB output sync enabled.
    0x2B 0x80 0x10 NTSC standard. SSAF luma filter enabled. 1.3 MHz chroma filter enabled.
    0x2B 0x82 0xC9 Pixel data valid. RGB and CVBS/Y-C out. SSAF PrPb filter enabled. Active video edge control en

    0x2B 0x87 0x80 RGB input enabled.
    0x2B 0x88 0x10 24-bit RGB input enabled
    0x2B 0x8A 0x0C Timing Mode 2 (slave). HSYNC/VSYNC synchronization.

    What causing this issue ?

  • Hai what changes did you made in the clock? iam receiving the black and white image on the screen the people with same issue also said that there is problem with input clock.But iam giving input 27mhz clock when i checked it with the oscilloscope it was 26.8Mhz hope that wont be a problem.Thanks!

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