Bare Bones VGA Signal

I’m trying to set up VGA signal timing in the simplest way possible. I’m just trying to display a few simple, still patterns - I’m working on building a custom video adapter and I’m trying to use the Arduino to test out timing. I made a simple sketch that’s supposed to display the left of the screen white and the right black. Pin 10 controls pixels, and is attached to a 4.7kohm resistor that’s attached to the R,G, and B pins of the VGA port. HSYNC and VSYNC are plugged directly into the Arduino’s IO header.

I hooked up a cable to my monitor, and it’s giving me a flashing message box that says the signal is out of range. I think I’ve got some of my timing off, but I’m not sure how to correct it.


void setup() {
  pinMode(10, OUTPUT);
  pinMode(9, OUTPUT);
  pinMode(8, OUTPUT);

  digitalWrite(10, LOW);  //pin 10 is VSYNC
  digitalWrite(9, LOW);   //pin 9 is HSYNC
  digitalWrite(8, LOW);   //pin 8 is pixel data

void loop() {
  digitalWrite(9, HIGH);
  for(int i=0; i<480; i++)
    digitalWrite(8, HIGH);
    digitalWrite(8, LOW);
    digitalWrite(9, HIGH);
    digitalWrite(9, LOW);
  digitalWrite(9, HIGH);
  digitalWrite(10, HIGH);
  digitalWrite(10, LOW);
  digitalWrite(9, LOW);

Does anyone know what might be happening? Is delayMicroseconds not precise enough?

Delay microseconds only has resolution of 4 microseconds. Also digital write takes about 65 clock cycles so you need to use direct port addressing.