I would seriously consider the above advice on the 1881 chip. However, if you just *must* do it with a pic, here is one way...
Schematic:
Basically, detect the horizontal sync pulses and then look for the wide ones that denote vertical sync.
Don't even go here. Just get yourself a sync separator chip like an EL1881 and the whole job is done for you.
dPearce Consulting
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martin
"An eye for an eye makes the whole world blind" Gandhi
Hi,
What would be the simplest way to detect the vertical sync with a pic (16f628) chip on a PAL video signal ?
Everything i google up is quite complex as it does a whole lot more than i want. The only thing i care about is to trigger an event for each vertical sync that passes my way.
Any suggestions would be great :)
Alex.
Hello Alex,
Assuming you are dealing with composite video I second the opinion of the others, to get a decent sync separator chip such as the LM1881. Ok, it's over a Dollar but consider this:
For a decent V-Sync locking under noisy conditions you need to run at least an integrator. Sometimes I went as far as a PLL (which low cost sync chips usually don't have). More important is that in nearly any video application you need to clamp the black level because most incoming signals will arrive AC-coupled. Chips like the LM1881 generate a black level clamp pulse. Sometimes that is called black porch clamp. This is also the time slot where the chroma burst is found.
Regards, Joerg
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