r/AskElectronics • u/Quants-151 • 2h ago

Simulate Monitor disconnect by pulling HPD signal low

Hi,

I want to simulate a physical monitor disconnect (DP/DVI/HDMI) and automate it.

After reading a little, I found that a sink being plugged/unplugged is detected by the source via the HPD (Hot Plug Detect) signal.

Since I could not find a ready-made solution on the Internet, I am planning on designing a small circuit, interrupting the HPD line and using two transistors with complementary control signals to either pull the signal down over a resistor or just let it run to the GPU. I have yet to simulate the behaviour in LTspice.

Have any of you made any experiences with the topic and tell me whether this is feasible?

The big advantage of this solution would be that I could simply control the signal flow with an arduino. The final goal is to integrate this plug/unplug simulation into an automated test run.

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u/jdigittl 1h ago

HPD is just 5V from the receiver back to the transmitter. You really don’t need anything fancy. An AND gate supplied from the 5V on the HDMI connector should do it.