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SN75DP130: Displayport Redriver

J-ZHOU8
Intellectual 2690 points
Part Number: SN75DP130


Tool/software:

Hello experts

Hope this finds you well.

I am trying to change the SCL_CTL and SDA_CTL pins I2C for SN75DP130SSRGZ.


We think: If you change bit 7 of Offset 05h from 0 to 1 and change bit 4:3 value of Offset 15h, Preemphasis will change by 10%


The waveform changes as we want, but even if I change the EQ setting between Offset 05h and 0Ch, there was no change in waveform.
(If you change the bit 4:3 of 15h, you can see a change in the waveform, so I think that it is successfully accessed to I2C and write the value properly, but the EQ setting does not change.)
I looked at HBR1 and HBR2, and I didn’t feel any change in both.

https://www.ti.com/jp/lit/an/slla349/slla349.pdf?ts=1734066680261&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252Fja-jp%252FSN75DP130

I looked at this page and it says that Link training is disabled, but when Link training is disabled, it stopped and did not show anything even when the monitor is connected
Is there a procedure to turn Link training back on at the end?

Regards,

Jieyu 

  • +1
    TI__Mastermind 41340 points

    Hi Jieyu,

    what are you changing the values to in register 0x15h? 

    Its odd that the pre-emphasis and the EQ are mutually exclusive here. Is there a reason you want to set the pre-emphasis manually? 

    J-ZHOU8 said:
    Is there a procedure to turn Link training back on at the end?

    This will not work, as the manually selected pre-emphasis values will be reset.

    Link training for DisplayPort will reset all TX swing and pre-emphasis values and determine the best combination of the two for the link. Turning on link training at the end would reset the manual configuration done.

    When link training on this device is turned off it will no longer snoop the AUX bus, so the link training registers can be manually set. 

  • +1 in reply to Vishesh Pithadiya
    TI__Mastermind 41340 points

    Hi,

    I'm closing this thread due to inactivity