Updating readme with a note on HDMI Out cable.

README.md

@@ -8,7 +8,7 @@ This branch contains sources for the Arty Z7-20 Out-of-Box Demo.
 
 This repository contains the Out-of-Box Demo for the Arty Z7-20. It similar to the demo that comes preprogrammed on the board when shipped to customers. The demo uses a wide range of the board's peripherals, including the HDMI video inputs and outputs, audio output, LEDs, buttons, and USB-UART bridge.
 
-The demo forwards signals from the HDMI input port to the HDMI output port. To use this feature of the demo, an HDMI capable computer and an HDMI capable monitor are required, as well as two HDMI cables.
+The demo forwards signals from the HDMI input port to the HDMI output port. To use this feature of the demo, an HDMI capable computer and an HDMI capable monitor are required, as well as two HDMI cables. If there is no image on the monitor, please disconnect and then reconnect the HDMI Out cable.
 
 When any button is pressed, an audio sample is generated by the Zynq processor and is streamed out over the audio output jack for approximately 4.5 seconds. The sample generated is a 261 Hz sine wave, also known as the musical note C4.