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When I try to write to I2C registers of the ADI HDMI transmitter, the register values do not change.  What is going on?

  • When Hot-Plug Detect (HPD) is low the HDMI Tx will automatically go into power down mode.

  • After an HPD interrupt, register 0x41[6] must be set to ‘0’ to power up the part

  • During power down all registers except for 0x97 – 0xAF are reset to defaults

  • Most HDMI Tx devices (except AD9889, AD9389, AD9387, ADV7520, ADV7521) have an "HPD Override" function
    • These devices will operate same as if HPD = 1 when HPD "override" is enabled
      • On the ADV7510, the registers will reset on an HPD = 1 -> 0 transition

      • On the rest of these HDMI Tx devices the registers will not reset on an HPD = 1 -> 0 transition
    • HPD state and interrupt registers remain avaiable even of HPD Override is enabled