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I am designing a board which converts DisplayPort to LVDS, in order to drive cheap panels from older notebooks or off ebay. DP is free of charge, compared to HDMI, and a simple converter IC is available using the PTN 3460.

My first draft used a full size DP connector. Pins 15+17 for aux, pins 10+12 for lane0 and 7+9 for lane1. It is the sink-sided pinout of the DP specification, as wikipedia states:

https://en.wikipedia.org/wiki/DisplayPort

It works... kind of... The mechanical tolerances of DP plugs seem to be pretty bad, or I bought a bad series. I really have to press the connector in, with a lot of force and I need both hands to achieve a stable image. I couldn't take a picture because of that :) Thats why I removed the DP and added an mDP receptacle. Saves some space as well, so why not.

Again I used a pinout from the web, e.g. wiki egain:

https://en.wikipedia.org/wiki/Mini_DisplayPort

The lanes are again crossed, I just did a continuity test. The mDP is connected to my board, and I am probing into the open end (full size DP) I unplugged from my notebook:

Pins 1+3 end up on the PTN's lane0 input, pins 4+6 on lane1 and aux on pins 15+17. Ground, config1 and config2 and hot plug are also connected correctly.

But: nothing. The board is not even getting recognized. Where can I start to search for the the problem? The only thing I did was replace a dp receptacle with the mini dp version of it. I also tried several cables, no change.

I also attached two images, showing both board versions from the top. Blue is top layer, green is the third layer and red is the bottom one. The resolution is 1600x1200 for my test panel.

Displayport

mDP

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  • \$\begingroup\$ Do you have a ground plane below the differential pairs? Does the aux pair has a ground plane? What are the two components connected to pins 4 and 6? \$\endgroup\$
    – Lior Bilia
    Jun 23 '20 at 20:36
  • \$\begingroup\$ perhaps you are purchasing junk plugs \$\endgroup\$
    – jsotola
    Jun 23 '20 at 20:38
  • \$\begingroup\$ Looks like you may have your AUX N & P reversed on the mini pinout. \$\endgroup\$
    – brhans
    Jun 23 '20 at 20:46
  • \$\begingroup\$ Concerning to en.wikipedia.org/wiki/Mini_DisplayPort, the Auxiliary pins have to be exchanged. \$\endgroup\$ Jun 23 '20 at 20:55
  • \$\begingroup\$ My bad, one thing I forgot: I can swap the P/N in software on both the lanes and the aux. But I have to swap them all, right? \$\endgroup\$
    – PhreakShow
    Jun 23 '20 at 21:01

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