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I have designed board that carrier transmitter HDMI module. There are TX side and RX side, the board works well except one issue that which takes a lot of sleepless days from me. this is the description of the system: enter image description here

  • Test pattern board (TPB) is board that transmit constant pattern regularly. (I test it separately to check if LCD get the pattern and it works)
  • MB TX BOARD is the board that I designed that carrier transmitter TX module
  • MB RX BOARD is shelf product that carrier receiver RX module (same company module TX).

The issue is the video working ONLY after:

  • I connected the TPB (Test Pattern Board) to screen with HDMI cable
  • I saw some video on the screen - ok -> remove the HDMI cable again
  • Take the cable and connect again the TPB to MB TX board
  • now the video working and transmit to other side

I think at the beginning maybe screen send an HPD signal to TPB (Test Pattern Board), but the MB TX board sent it too. What could be the problem that the TPB connects to the screen and then to my board so it only transmits?

EDIT: The TPB does not need any EDID/HPD, it transmits anytime, now when I connect the TPB to another board with an HDMI connector (the other board without any voltage) it works too!!! Maybe it's ground issues>? the HDMI has Chasis and GND separately that are not connected.

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    \$\begingroup\$ wow! HDMI is a pretty broadband system with multiple parallel lanes! Kudos for designing this! \$\endgroup\$ Commented Jun 15, 2022 at 19:36
  • \$\begingroup\$ @MarcusMüller what? \$\endgroup\$ Commented Jun 15, 2022 at 19:40
  • \$\begingroup\$ I just said "It is a hard problem you solved! I admire that." \$\endgroup\$ Commented Jun 15, 2022 at 19:43
  • \$\begingroup\$ @MarcusMüller I didn't solve it, I just want some help from other peoples, this is not a solution to plug in the cable and remove it and connect again to my board, I want something that works regulary. \$\endgroup\$ Commented Jun 15, 2022 at 19:45
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    \$\begingroup\$ Are you handling EDID? \$\endgroup\$ Commented Jun 15, 2022 at 20:14

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