1. Home
  2. Electronics Design
  3. Clean-up RS232 Signal

Clean-up RS232 Signal

Hello All,

This may be more suited to .basics, but I'll try here and prepare for the possibility of being chastised for not addressing the appropriate group :-).

Couple of questions regarding a RS232 signal, btw this is on both sides of the 232 shifter. When looking at the signal on the 'scope the leading edge over shoots by about 10-15% of the total level before it settles.

  1. Does this matter? (i.e. is it sloppy?)

  1. How does a non-EE correct the problem... I would assume it would be quite similar to the way an EE would, but it would be explained in laymans' terms and possibly at a slower pace for the cognitively impaired?

Thanks,

John

Reply to
jecottrell65
Loading thread data ...

Meaningless without knowing the setup and how it's being probed.

1) Is your probe compensated? 2) Is your ground lead short? 3) What about the falling edge?

No, it's fine if it's the signal. There's no return on investing time and thought to get textbook waveforms in this situation.

He opens a beer because if that's all you have to worry about, your project works great!

Reply to
a7yvm109gf5d1

You are probably seeing an artifact of a poorly adjusted 'scope probe. Find the little screwdriver adjustment and turn it until the overshoot just disappears. See the bottom of the following page:

formatting link

-- Joe Legris

Reply to
J.A. Legris

Fluke 199B

10:1 probes, stock length

This is more of a curiosity thing than anything else. I've always had good success with my projects but as I get deeper into things I'd like to learn more.

Thanks,

John

Reply to
jecottrell65

Welllll.....

I wouldn't calibrate a scope probe using the signal under test as the reference. I'd probe the scope's own calibrator, if it has one. I don't know how to calibrate a probe without a "trusted" reference, although a reference could probably be made pretty easily with today's CMOS and stuff. :-)

Good Luck! Rich

Reply to
Rich Grise

On a sunny day (7 Dec 2006 13:45:16 -0800) it happened snipped-for-privacy@gmail.com wrote in :

Assuming you calibrated the scope probe :-) no it does not matter. the signal is limited, and sampled halfway the bit time anyways.

Reply to
Jan Panteltje

Isn't this just Gibbs Phenomenon? If that is the case your equipment is working fine and calibrated correctly. The overshoot is just a consequence of trying to make a waveform with a discontinuity. Mathematically I think the overshoot is 9%. Just do a wikipedia search to see if that is what is happening to you.

formatting link

Reply to
white.brad

That should be a clue-- It's unlikely a line driver IC is going to by concidence seem to act as an analog amplifier and preserve the ringing. Try a direct connection to your scope thru a short piece of coax and it will probably look better.

Aalso don't worry about the ringing, the RS-232 specs require the signal to be sampled at the + and minus 3 volt points IIRC, so any ringing at the 12 volt extremes is just eye-candy.

When looking at the signal on the 'scope the

Reply to
Ancient_Hacker

On a sunny day (10 Dec 2006 15:43:02 -0800) it happened snipped-for-privacy@gmail.com wrote in :

I think Gibbs is the other way around, from that page: J. Willard Gibbs pointed out in 1899 that the oscillations were a mathematical phenomenon, and would always occur when synthesizing a discontinuous function with a Fourier series.

He is not doing a reverse Fourrier.

Reply to
Jan Panteltje

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.