Normally all HDMI source device will stop transmitting the signal if there is no sink device connected. For the source measurement to make the source transmit the signals following steps needs to be taken: Connect the HPD pin to 5V using a pull-up resistor (500 Ω to 1KΩ ) Connect the 3.3V power supply to the VCC input (In the test fixture). Connect and configure the EDID emulator to the required device resolution.