Explaining how to generate a fairly high resolution composite video signal from an Arduino UNO (or Nano or similar) using just three resistors. The signal is up to about 380 pixels wide by 270 pixels high. The UNO doesn't have enough RAM to hold bit mapped graphics that size, so you're limited to text or other block-graphic style displays. The Arduino Mega 2560 has much more RAM, and four serial ports (the video generation ties up one of the serial ports), so is better suited to this kind of task. The resistor values aren't that clear because of my scribbly handwriting. The one from pin 1 is 1000 ohms, the one from pin 5 is 47 ohms, and the one from pin 9 is 1200 ohms.
You can download the sketch using this link: https://ceptimus.co.uk/CompositeVideo...