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[on:]

Hey. Two main questions.

If I increase the PWM frequency, noise on nearby wires should reduce? I'm running a twisted pair carrying composite video next to my power cable running PWM, and at around 40% duty cycle, the picture gets so corrupted that it's unviewable. Would increasing PWM frequency help?

I've read the following thing.
http://arduino.cc/en/Tutorial/SecretsOfArduinoPWM

As far as I know, Serial is also dependent upon Timer0. I'm only changing the prescaler bit, so Serial shouldn't be affected whatever I do to the prescaler?

Cheers.

[Reply #1 on:]

Would increasing PWM frequency help?

No.

I'm only changing the prescaler bit, so Serial shouldn't be affected whatever I do to the prescaler?

Why not, it is a prescaler if affects everything that follows it.

[Reply #2 on:]

Well, to be honest, I thought Serial drew it's clock directly from the main 16MHz crystal. There's also this post by RuggedCircuits

http://arduino.cc/forum/index.php?topic=96479.0 (2nd Post)

I was under the impression that changing timer0 only changed the delay() and millis() functions.

[Reply #3 on:]

Hey. Two main questions.

If I increase the PWM frequency, noise on nearby wires should reduce? I'm running a twisted pair carrying composite video next to my power cable running PWM, and at around 40% duty cycle, the picture gets so corrupted that it's unviewable. Would increasing PWM frequency help?

I guess you are assuming that there is a "coupling" of sorts between the pair carrying the PWM signal, and the pair carrying the video...what Category cable are you using?

If you are using good quality CAT-5 or even CAT-6, I think this should not be the case....but if it is, then I think you should use the twisted cable to carry say the digital signal, and maybe break out your video signal to a good quality shielded cable....

this might resolve your issue... varying the frequency will have an effect on the coupling, but if you really have this much interference, I do not think it will help much...

[Reply #4 on:]

Lets be clear, do we mean the hardware serial or some software serial library?  Hardware serial is self-contained circuitry, it doesn't share with anything else and has its own baud-rate prescaler register.