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SN75DP159: HDMI Compliance Testing

Martin Seeger
Expert 5381 points
Part Number: SN75DP159

Dear Team,

our customer wants to use DP159 but runs into issues during the HDMI compliance testing. Below their description.

Any advice is very much appreciated.

Best Regards
Martin

Currently we are developing a product with an HDMI output based on a Xilinx Ultrascale+ FPGA and a SN75DP159RGZ. We have the HDMI output operational when it is connected to a monitor.

To make sure that our output is compliant with the HDMI standard, we want to do a compliancy test. We use a HDMI2-TPA-P adapter in combination with a Tektronix MSO73304DX scope.

Unfortunately, we have some issues in creating an output signal at the HDMI output connector when the compliancy tool is connected. The HPD pin is forced high, which should enable the output.
We see that the FPGA streams the TMDS signal towards the DP159. Though, the DP159 seems to block the signal and does not output it to the HDMI output connector.

When looking at the i2c control registers we see no differences between the state where a monitor is connected compared to the state where the compliance tool is connected:

Register

Register value
Monitor connected

Register value
Compliance tool connected

0x09

0x06

0x06

0x0a

0x31

0x31

0x0b

0x80

0x80

0x0c

0x48

0x48

0x0d

0x00

0x00

0x0e

0x00

0x00

0x0f

0x0f

0x0f

0x10

0x00

0x00

0x11

0x00

0x00

0x12

0x00

0x00

0x13

0x00

0x00

0x14

0x00

0x00

0x15

0x80

0x80

0x16

0x00

0x00

0x17

0x20

0x20

0x18

0x00

0x00

0x19

0x00

0x00

0x1a

0x00

0x00

0x1b

0x00

0x00

0x1c

0x00

0x00

0x1d

0x00

0x00

0x1e

0xa8

0xa8

0x1f

0x0f

0x0f

0x20

0x0a

0x0a

What is preventing the DP159 from outputting the HDMI signal?

And how can we force it to output the signal?

  • 0
    TI__Expert 5381 points

    Adding to the opening post: The customer noticed some differences in registers 0x44, 0x48, 0x49 and 0x4a - for page 1:

    Register

    (page 1)

    Register value
    Monitor connected

    Register value
    Compliance tool connected

    0x44

    0xff

    0xea

    0x48

    0x07

    0xfc

    0x49

    0x03

    0xf8

    0x4a

    0x07

    0xfe

    Any meaningful information behind those values?

    Unfortunately this part is not documented in the data sheet.

    Best Regards
    Martin

  • 0 in reply to Martin Seeger
    TI__Guru**** 154671 points

    Martin

    Do they have an EDID emulator connected as part of the setup? The emulator emulates a sink device that enables the handshake of the signals.

    Page 1 0x44, 0x48, 0x49, 0x4A are RX CDR interloper phase codes for different lane and are expected to change.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Expert 5381 points

    Hello David,

    thanks for the reply and the details about the registers.

    Regarding the setup, please find below some more details from the customer:

    I am not using an EDID emulator. I connected the DDC, HPD and PWR to a monitor (the same monitor with which the HDMI output is functional with a standard HDMI cable).

    In this way, the DP159 can access the EDID of the monitor.

    The FPGA is outputting the TMDS signals to the DP159 (verified using scope), but the DP159 does not output the TMDS signals to the HDMI connector.

    If I connect this setup to the HDMI output of my notebook (Dell Lattitude), I measure the TMDS signals. So, at least for the notebook, this setup is working.

    Best Regards
    Martin

  • 0 in reply to Martin Seeger
    TI__Guru**** 154671 points

    Martin

    For the Tektronix P7720 probe, do they set the termination voltage to 3.3V? 

    The offset voltage range of the TekFlex solder-in tips is -4 V to +4 V, which is adjusted using the Probe Setup screen of the oscilloscope or the offset knobs on the oscilloscope front panel. Using the offset voltage controls, it is possible to make measurements within any 2.5 Vp-p window between -5.25 V and +5.25 V. For example, by setting the offset voltage to +3.0 V, it is possible to measure an HDMI signal, which has a signal swing between about +2.8 V and +3.3 V.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Expert 5381 points

    Hi David,

    thanks for the answer - below the customer's feedback:

    The problem is not in the measuring equipment/setup as it works perfectly for a laptop HDMI output.

    It really seems the DP159 is not outputting any signal (tmds/clock).

    Best Regards
    Martin

  • 0 in reply to Martin Seeger
    TI__Guru**** 154671 points

    Martin

    Please see this e2e ticket: https://e2e.ti.com/support/interface/f/138/t/568900?SN65DP159-Why-does-the-DP159-outputs-turn-off-when-a-cable-is-disconnected-.

    The DP159 works with a monitor, so it looks the design itself is OK. 

    The HDMI is a DC-coupled 3.3V interface, so the DP159 has to see the 50ohm to 3.3V in order to enable its output? Have the customer tried to put the 50ohm termination to 3.3V on the DP159 output?

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Expert 5381 points

    Hello David,

    the customer informed me that it was indeed the termination. Setting it to 3.3V solved the issue!

    Thanks and best regards
    Martin