TMDS181: HDMI 4k video in source mode setup

Hi,

Does the design work with a non-4k resolution?

For the 4k resolution, can you read the TMDS_CLK_RATIO_STATUS bit and verify it is "1"?

Can you also measure the TMDS181 clock output? What is the clock output frequency?

Thanks

David

Hello David,

Thanks for a quick response.

Without any configuration register changes through I2C, device works as is and windows considers the maximum resolution up to FHD only not 4k.

TMDS clock on the HDMI connector displays 150MHz.

Hello David,

Thanks for a quick response.

Without any configuration register changes through I2C, device works as is and windows considers the maximum resolution up to FHD only not 4k.

TMDS clock on the HDMI connector displays 150MHz.

Hi,

Are they trying to do 4k@30Hz or 4k@60Hz? 

For 4k@60Hz, the TMDS_CLK_RATIO_STATUS bit must be set to 1. 

When changing to 4k@60Hz, does the source turn off its output, make sure the TMDS_CLK_RATIO_STATUS bit being set to 1 before enable its output again?

Thanks

David

At first, we tried to write the TMDS_CLOCK_RATIO_STATUS to 1 however the screen doesnot flicker.

we tried to write register 0x0A to value 0x33 and register 0x0B to value 0x1A.

we tried to read every 1 sec the control registers with address 0x09, 0x0a and 0x0b however the values we read 0x02, 0x00 and 0x00 every time respectively.

Hi,

Is this 4k@30Hz or 4k@60Hz video resolution? 4k@30Hz is still HDMI1.4 and you would leave TMDS_CLOCK_RATIO_STATUS bit to 0. For 4k@60Hz, you don't have to set it. The source will write to the TMDS_CLOCK_RATIO_STATUS bit in the monitor DPCD registers and TMDS181 will snoop it and set its own TMDS_CLOCK_STATUS bit accordingly.

Thanks

David 

Hello David,

We tried to verify almost all the aspects.

1. power up is in the nominal range with delays respected.

2. DDI channel has EDID data transferred and HPD is also reflected as per the source mode.

3. Without configuring, we tried to read the ctrl registers 0x9 to 0x0C and values are always 0x02, 0x0, 0x0 and 0x0 respectively.

4. if we configure the addresses 0x0A with 0x12 and 0x0B with 0x31 yet the same results as shown in the point 3.

moreover, there is no flickering of the display even when we configure register 0x0A and 0x0B.

From the results above, seems that the retimer always snoops and configures the TMDS_CLOCK_RATIO_STATUS in 0b0 value.

Any thing we can suffice to get the testing further?

Hi,

Looking at the schematic, the input is AC coupled. In this case, you do not want to use TMDS181 as the TMDS181 input supports DC-coupled. You need to use DP159 which supports AC-coupled input.

Thanks

David

We will give a try with SN65DP159 since it is pin compatible IC.