Recently, I could generate successfully a 640x480 @70Hz via Mega 2560. I do not focus on pixel information, but on the stable V and H sync. That works good (time to time a small glitch... but it's ok).
The thing is, that code is very tight to current processor speed, full of NOPs and adjustments on calculations according to the standard definition of that particular resolution, so not the best thing in the world and I want to code this properly.
I thought that having an external crystal oscillator at the proper frequency could solve the problem, so I got a few, and tried to connect one of them.
The system is basically:
+3.3 -> Crystal -> Input Pin (2) with attachInterrupt on CHANGE.
The problem is... the ISR is not being fired. I am not an expert in electronics, obviously, so I googled a lot about how to plug crystals into circuits, but not much information about specific details (i.e. you need a resistor blahblah...).
So, basically, I would love if somebody could help me out understanding how a crystal needs to be connected to the Arduino to successfully be able to get its pulses.