i.MX8 Display Port Interface

[joséviníciusmel]

Hi,

I am working with the MCIMX8M-EVK and I need to use Display Port (DP). The i.MX8 processor supports DP through interface HDMI Display Interface.

My first question is aboug this interface. I was unable to find any information about DP pins in i.MX8 documents. However, in some SOMs (System-On-Module) datasheets this information can be find. In the Figure 1 it is possible see this relation. Are these pins correct to DP connection?

My second question is related the MCIMX8M-EVK HDMI connector. My intent is used this connector (with a adapter) to use like DP output. But in the schematics it is possible see that HDMI_HPD and HDMI_AUX_N are tied together. Is it possible use some adaptor with this limitation?

Thanks!

[Alex1990]

Hi. I`m working with my own board with IMX8M and want to use DisplayPort inteface through usb type-c alt mode. Is attached schematic right for my case? Are there any news about linux bsp updates for dp support? Thanks!

[guido_gunther]

bernhardfink‌ are there any gerbers / boms for the above adapter that i could grab to build one?

[bernhardfink]

No, sorry, just the schematic.

Regards,

Bernhard.

[bernhardfink · Accepted solution]

Besides the physical conversion between the HDMI and the DP signal mapping, the software BSP needs to support the Display Port as well.

And this is not the case, neither in the current Linux BSP nor in Android. It might come in the future, but for now it's not supported.

For basic system verification during validation we used a small plug which converts the HDMI plug into a DP plug:

[sanum19]

Could you please provide any information on whether the software BSP now supports DisplayPort? 

[joséviníciusmel]

Hi guys!

Thanks for your answer.

I will use this HDMI-DP Bridge like model, but I have some questions.

1) In my first figure, the pair HDMI_TX_M_LN_0/HDMI_TX_P_LN_0 is referred like DP LANE 0 NEG/DP LANE 0 POS, but in the HDMI-DP Bridge example the HDMI_TX_M_LN_0/HDMI_TX_P_LN_0 was used to this lane. Do I need be careful with this pins?

2) In MCIMX8M-EVK the four DP lanes are pulled down through 604 ohms resistors. Is it a problem to used this DP adaptor with these pulldown resistors?

3) In the HDMI-DP Bridge example the we can be see that DDC and CEC pins need be pulled down, but in the MCIMX8M-EVK these pins are pulled up. Is it a problem keep these pins pulled up?

4) The fact that software support to DP will be released in the future is not a problem, but the do NXP have some date to this software release?

[bernhardfink]

Hi José,

1. The lane order in DP is different than in HDMI:
   -  HDMI D0 goes to DP2
   -  HDMI D1 goes to DP1
   -  HDMI D2 goes to DP0
   -  HDMI CK goes to DP3
2. The pulldowns on the HDMI lines on the 8M EVK must be removed when used for DP purposes
3. Yes, if you work with an add-on plug converter you need to change these pull-ups into pull-downs, so remove them from the 8M EVK
4. I don't have a clear date yet, but I will keep you informed.

The connection based on this adapter looks like this:

-  an 8M EVK is prepared for this setup (resistors mentioned above changed/removed)

-  from the 8M board a short HDMI cable goes to the HDMI-DP adapter board (HDMI-A to HDMI-A)

-  the required remapping of the signals take place on the adapter board

-  the DP jack on the adapter board connects directly to a DP connector of a monitor

Regards,

Bernhard.

[Banderson]

Hi Bernhard,

Does your answer to point 1. remain the same if using a 2-lane displayport (eDP) connection?
i.e:
- HDMI D2 goes to DP0
- HDMI D1 goes to DP1

[smusserRosen]

Hi Banderson,

Was this found to be true? It should be. I currently have a two-lane setup with eDP. The auxiliary communication works well, and the link training detects two lanes. However, I am unable to get transmission.

Thanks

[joséviníciusmel]

Thanks Bernhard!

[igorpadykov]

Hi José

for eDP signal descriptions and connections one can look at eDP specification

since Reference Manual sect.13.4 described that hdmi module complies with DisplayPort Specification,

Version 1.3. As for HDMI_HPD and HDMI_AUX_N, there are no issues for eDP usage, as they muxed

with eDP_HPD and eDP_AUX.

Best regards
igor
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[joséviníciusmel]

Hi Igor! Can you answer the questions below?

Thanks!