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I noticed that several contacts on a typical HDMI connector are listed as unused. I'm curious, does this mean they are unused in typical HDMI communication protocol, or does this mean they are physically unused?

I'm attempting to re-purpose an HDMI connector and cable to send non standard HDMI signals, thus I'm curious if I can actually use the unused pins.

Question: do HDMI cables have conductors for the 'unused' pins?

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    \$\begingroup\$ If this cable was manufactured for a specific purpose, not needing some signals, there is a good chance that there won't be corresponding conductors, as extra conductors are increasing the cost of the cable. But! It could be that the manufacturer of the whatever appliance the cable if from, just decided to use some off-the-shelf ready made standard cables. So you should make your tests.. \$\endgroup\$
    – Eugene Sh.
    Commented Jul 22, 2016 at 14:15
  • \$\begingroup\$ I hope you are doing this adaptation of the HDMI connector for your own use in an single use application. There is nothing worse that you can do to take a standard protocol/usage connector and bend it to an alternate application on a mass produced product. There are already plenty of connector types available that are general purpose in nature or types that have been forced into general purpose usage by industry. The Dsub-9 connector is an example of the latter. \$\endgroup\$
    – Michael Karas
    Commented Jul 22, 2016 at 15:40
  • \$\begingroup\$ @MichaelKaras Hello, thanks for the response. There were several reasons why I've decided to go with an HDMI connector. 1) Form factor - I need a connector that is less than 1/4" in height and is compact. 2) I need a connector that has at least 12 conductors. 3) This device will only be used by a limited group of technicians and engineers, thus I'm not concerned with improper usage of plugging stuff in. I've also looked into edge connectors but the dimensions were just too bulky. I'm very open to finding a different connector, however, I've just had no luck. \$\endgroup\$
    – Izzo
    Commented Jul 22, 2016 at 16:35

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On a normal Type A HDMI connector, all pins have an assigned usage. Except for pin 14, which depending on the HDMI version is Reserved (unused) or used for Ethernet or other odd uses. While an individual device may not use all 19 pins, a typical HDMI compliant cable should have at least 18 of those pins wired on both ends.

If you are trying to use an HDMI connector for your own purposes, that's up to you, but if you want it to work as HDMI AND your custom wiring at the same time, it won't be possible.

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There are no "unused" pins in an HDMI cable. A device may not use all of the pins (like Ethernet or return-audio, as examples), but those functions are assigned to pins. So, for a cable manufacturer to be able to use the HDMI logo, the would have to have all 19 pins wired-up.

Keep in mind that many pins are for differential signaling (8) and some are shields (4), so you need to select the pins that you use carefully.

Here is the HDMI pin-out from Wikipedia: https://en.wikipedia.org/wiki/HDMI

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