HDMI as General Purpose Input/Output(GPIO)

[arielcosep1996]

I was kind of wondering if I could able to make its pins as Input/Output. E.g. All data pins output is high that could able to lit an led connected to them.

 

[Someone Somewhere]

Not that I know of. Differential outputs aren't meant to deliver much current, and are probably floating, not DC coupled.

 

[InvalidError]

The cables and connectors are just dump wires and metal, you can put whatever you want through them up to their current and voltage rating if you use custom boards at both ends.

If you want to drive the HDMI cable using a GPU though, the GPU's TMDS transmitter is not designed to send DC, it is designed to send DC-neutral differential signals by expanding the coding space to ensure the total number of 0s and 1s sent over a two words window is always equal - every byte in gets expanded by two extra bits and if the next word would increase any existing imbalance, the pattern gets inverted to prevent the DC bias from increasing. TMDS also guarantees a minimum number of 0-1 transitions per word to help PLLs recover the clock signal and maintain lock.

As SS said, the GPU's outputs into the cable are also most likely capacitively coupled.

You won't be able to directly drive LEDs from a TMDS driver since TMDS signaling is designed specifically to eliminate DC bias from its output.

 

[arielcosep1996]

So in other words it is impossible? I thought that I could able to manipulate the data like Parallel port.

 

[Someone Somewhere]

Don't think so. Parallel ports are a pretty slow and basic method of communication. HDMI ports are way way way faster, and they need to do very clever things with the circuitry to make that happen.

 

[InvalidError]

So in other words it is impossible? I thought that I could able to manipulate the data like Parallel port.

All the modern IO standards are based on TMDS signaling and to interface anything with those, you need a controller of some sort. Your best bet for low speed stuff would be a USB-to-RS232 serial port emulator chip.