I don't waste my time trying to help anyone anymore. All I get is insults, irrelevant "facts" and complaints about how what I said "won't work" (even though I've been doing it for eons).
It's like those green EE kids fresh out of school. They want to power an LED, run the numbers through Ohm's law and then start searching for the proper resistor... to three decimal places, then wonder why they can't seem to find a 121.294 ohm resistor (and if an old timer tells them that it's not so critical and that a 120, a 100 or even a 150 will work just fine), they don't want to hear it. After all, what can a guy who knows what a 5U4 is possibly know about those "silicon thingies"?
It's always worthy if it is free.Make sure the scope probe has good band width too..
Krupski, its an old threadI only revived it to discover what bandwidth scope was used.I have the chance to play with a 2GHz scope over the next couple of weeks and wondered if it is worth repeating some of the experiments.
Personally, I have used ccts. with and without a series resistor over quite a few years.I wouldn't jump up and down saying a resistor is needed, but if it makes someone feel better to do it their way, all the power to them.It's always nice to compare things.Having a high and low quality scope looking at the same signal might be interesting.OTH a series resistor is dirt cheap, oh what to do? .
Why repeat the experiments? I think they showed reasonable data. In fact, they proved "the point"... yes there is an
Also, what nobody seemed to mention (although I may have just missed it) is that the output drivers for the AVR pins, every time they switch, go through a very short period where they are BOTH conducting and placing virtually a short circuit across the Vdd supply (hence the need for bypass capacitors).
Us mortals do not get to play with this sort of equipment normally. Resistor may slow down switching but around here i think it best to suggest it as it gives some protection to the outputs from the inevitable silly mistake that the newbies (and others) make.
Agreed - another point I have not seen discussed is RFI from the switching transients.
"True for the hobbyist, but no engineer will spec a useless component for a mass produced product where the extra 1 cent is multiplied by millions of devices."A SMD resistor is 0.2 of a cent at 10,000 pieces. You are correct with this, but we are a home brew kind of place.Didn't think you were concerned about comerial manufacturing numbers.Engineers: allow vehicle ignition switches to fail resulting in death, allow faulty air bags manufacture causing death, allow software to circumvent pollution laws, allow a bridge to fall down. I just don't care about this damn resistor thing and I think you are there too..