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Modifying an HDMI dummy plug's EDID using a Raspberry Pi

cently found myself needing to change the monitor that a cheap HDMI “dummy plug” pretended to be. It was a random one I had bought on Amazon several years ago that acted as a 4K monitor, and I needed it to be something simpler that didn’t support a 4K resolution.

It was a random one I had bought on Amazon several years ago that acted as a 4K monitor, and I needed it to be something simpler that didn’t support a 4K resolution. In general this entails a pull-up resistor on pin 19 (HPD) to +5V, as well as a little I 2 C EEPROM chip containing the Extended Display Identification Data (EDID). As a quick explanation, this reads the entire EDID (probably 256 bytes in size) from the dump file created earlier, and formats it into an array of two-digit hex strings using od.

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