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DS90UB933-Q1: Use External PIXCLK issues

fabio ortolano
Intellectual 330 points
Part Number: DS90UB933-Q1

Hello 

we are debugging a board with DS90UB933 serializer (coupled with DS90UB934 deserialized) and we are facing problems using "PLL lock to PIXCLK". First we have to say that with external oscillator (32MHZ) on DES side we correctly receive 48 MHZ and LOCK is stable. Also on DES side we check REGS 0x55 and 0x56 and we found 0 errors.

After this test, we want to switch to PIXCLK mode. Our configuration is configured with MODE=ExternalOscillator (in GPO3) using resistors, but via I2C regs we set the following:

REG 0x3: 0xC2

REG 0x35: 0x0

With these configuration, we are still able to set the GPO from DES to SER, but DES does not receive nothing by SER (LOCK pin on DES blinks). Also we see that on SER side

REG 0xC: 0x7

That means "DES Error"

What is the right procedure to use directly the PIXCLK from sensor as reference? Have we to configure others registers?

  • 0
    TI__Expert 3390 points

    Hi Fabio,

    Just to confirm, initially you are in "External OSC Reference Clock" mode with an external clock value of 32MHz? This works fine but when you switch to "Pixel Clock From Imager as Reference Clock" Mode then you start to see some issues, is that correct?

    If on the 933 you set 0x03=0xc2, you are disabling i2c pass through. Leave this as default and set 0x03=0xC7.

    When reading register 0x0C[2], make sure you are clearing this register bit by reading 0x03[5].

    Regards,

    Mandeep Singh 

  • 0 in reply to Mandeep S
    Intellectual 330 points

    Hello

    thanks for your reply. I intentionally stopped I2C because the drivers from SER and DES are different. At the end, I found what was the problem with this issue and the other post (https://e2e.ti.com/support/interface/f/138/p/883598/3268877#3268877). For be able to switch from EXTERNAL to PIXCLK I was driving the same input of the SER with two signals in the same time coming from Sensor and from External clock of SER. Removed one of the two series resistor, PIXCLOCK issue and SPIKES on LV disappered. Now I'm able to see 1Mpx with 15mt cable, that's great!

    Thanks.