This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

HD3SS215: 2:1 sink HDMI appllication issue about DDC channel

Part Number: HD3SS215

Hello,

I use HD3SS215 as 2:1 sink HDMI application, like Figure 8 of datasheet but has a little different.

My design has two HDMI source (2 IC's HDMI Tx port) and are connected to port A and port B of HD3SS215 . And the port C of HD3SS215 is connected to standard HDMI connector.

My test result: (Setting AUX="M" 1.65V, DX="L" ; port A--> Port C; OE = 3.3V (VDD) )

Test 1: HDMI connector (Port C) is connected to monitor by HDMI cable.

   - Measurement : DDC_SDA (port C) is about 4V.  DDC_SDA(port A) is about 3V. 

Test 2: HDMI connector (Port C) is open.

   - Measurement : DDC_SDA (port C) is about 4V.  DDC_SDA(port A) is about 3V.  (the result is same to Test 1)

My design has only one pair of pullups,  (2K ohm in Port C)

PS: the HDA works well.

When DDC is working, the level change is about 200~300mV (4V~3.8V). So monitor can't get the DDC command. 

What is consider about this issue?

Best Regards

  • Hi Mentor,

    This problem happens in DDC_SCL?

    With HDMI connector open and sources turned off, what voltage do you see on DDC_SDA (port C) and DDC_SDA(port A)?

    With HDMI connector open and sources turned on, could you remove the PULL-ups on DDC(port c), what voltage do you see on DDC_SDA (port C) and DDC_SDA(port A)?

    High voltage in DDC is 4V and low voltage is 3.8V, right? Do you have scope captures to share?

    Regards