Good afternoon everyone.

I am trying to control a Samsung TV via Serial from a remote processor and I am trying to use spare installed HDMI cabling to do it.

Samsung does not have an open API for IP control of the TVs but this TV does have a "service" (RS232C) port. The processor is located near the AVReceiver and there are 3 HDMI cables between this location and the TV of which only 1 is in use. I do not want to run any new cabling between the two locations and instead want to repurpose one of the spare HDMI cables.

The info I have found on this can be found here:

Questions regarding using an HDMI cable to transmit SPI, I2C, and UART serial data?


SerialDB9 to USB > USB to HDMI > HDMI Cable > HDMI to USB > USB to SerialDB9 Serial DB9 to Serial 3.5mm seems like a massively overengineered solution to this problem. Deconstruction of the HDMI cable is possible. I'd like to avoid it as my hands struggle to manipulate any cabling thinner than an undersea power cable but its a backup option!

I've also got a backup to the backup which is to use an ethernet run. I would very much like to avoid this as ethernet is too useful to waste IMO but at least it's a solid and proven option should everything else fail.

If anyone has had any experience in this then please let me know.

  • \$\begingroup\$ How long is the cable run? RS422 on an HDMI cable seems like a better idea, then you're sending differential signals on a cable designed for differential signalling. \$\endgroup\$
    – Ben Voigt
    May 14, 2017 at 14:57

1 Answer 1


Using an HDMI cable for rs232 isn't a problem. A cable is a cable is a cable. As long as you are sure it won't be plugged into an HDMI device by mistake (typically not a problem in one off hobby projects). And length may be an issue, as forgiving as rs232 is. A few feet isn't a problem though.

Making your own adapters is the only practical solution you have. Get a db9 dongle and a HDMI connector. If wiring small pins is an issue, there are prewired db9 pigtails and something like this

enter image description here enter image description here

The second adapter would be HDMI to a 3.5mm Jack or pigtail.

  • \$\begingroup\$ this is pretty much exactly what I was hoping for. you mentioned cable length; we're looking at (roughly, I'm not entirely sure of the run) 20-30ft. I'm pretty sure I've used cables of 50ft before for serial comms so I dont think this should be a problem \$\endgroup\$
    – eto.ttnflt
    May 14, 2017 at 15:51
  • \$\begingroup\$ @eto.ttnflt just keep in mind there are other options. CEC over HDMI is one. And a IR solution is wireless. An arduino and IR diode would be enough. \$\endgroup\$
    – Passerby
    May 14, 2017 at 15:59

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.