Dummy Plug Gets Smarter with Raspberry Pi

[Doug Brown] had a problem. He uses a dummy HDMI plug to fool a computer into thinking it has a monitor for when you want to run the computer headless. The dummy plug is a cheap device that fools the computer into thinking it has a monitor and, as such, has to send the Extended Display ID (EDID) to the computer. However, that means the plug pretends to be some kind of monitor. But what if you want it to pretend to be a different monitor?

The EDID is sent via I2C and, as you might expect, you can use the bus to reprogram the EEPROM on the dummy plug. [Doug] points out that you can easily get into trouble if you do this with, for example, a real monitor or if you pick the wrong I2C bus. So be careful.

In [Doug’s] case, he wanted to drop a 4K dummy plug to 1080p, but you could probably just as easily go the other way. After all, the plug itself couldn’t care less what kind of video you send it. It drops it all anyway.

Want to know more about HDMI? We can help out with that.