I wonder if it would be Schroedingers cat? or Delthe Cat?

Bill

I agree with you, Del. Synchronous communication is especially sensitive to noise, because any parasitic transition in the clock line may corrupt a big chunk of data being transmitted. And scopes very often seem to "fix" the problem.

For long wirings an RC termination may help. I mean a capacitor (roughly around 100 pF) connected in series with a resistor of 470 Ohm – 1K. These values are, of course, just estimates. Ferrite beads may be helpful, too.

However it would be worth to spend first a little time on the root of the problem:

- Keep the wiring as short as possible.

- Make sure you are using proper ground connections.

- Use shielded cables (except for very short distances). Ground the shield at only one end (usually the transmitter's, in this case the master).

- Keep the wiring away from noise sources. In doubt, consider any electric/electronic device as a potential source of noise.

- Be aware that shielding may be 100% effective for electric noise isolation, but magnetic noise won't be totally cancelled.

For many years I've been using piezoelectric lighters to test noise immunity in communication lines. It is really amazing how easily you can freeze an old-style PC keyboard (which communicates synchronously) by simply triggering a piezo lighter near the cables (not necessarily close to them). As the uC communicating with the KB was also used for other internal purposes, the whole PC could get frozen!

For many years I've been using piezoelectric lighters to test noise immunity

Me too

Del

I've been working with serial comms for quite sometime; integrated data acquisition systems. Never heard of using a piezo' lighter to test noise immunity though. I'm adding one to my field kit. Thanks for the tip y'all.

I have never had any luck getting a piezoelectric to burn, how do you light one?