Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How do you capture this long waveform?

  1. Jan 20, 2009 #1
    I have a 1sec serial data stream and my cheap PC based oscilloscope cannot capture it with good enough resolution where I can read the data.

    What can I do to capture this serial data stream with good resolution? My scope has only edge trigger function.

    I'm thinking of building a circuit that will output a delayed trigger pulse. I hope that this will allow me to capture the stream part by part. Is this a good idea or is there a better way?
  2. jcsd
  3. Jan 20, 2009 #2


    User Avatar
    Science Advisor

    Can you decrease your sampling rate? Alternately, if it's serial data, why not just capture it using a terminal program (for instance, TeraTerm if you're using Windows)
  4. Jan 20, 2009 #3
    when you say decrease sampling rate, you mean increase the time/div? I can capture the whole serial stream but then I can't zoom in enough to read the serial data.

    I can't use a terminal program because it is not your typical rs232 serial data. It's some weird format that I haven't figured out yet. It's about 30-40 bit long per frame.
  5. Jan 20, 2009 #4


    User Avatar

    Staff: Mentor

    Sounds like you're trying to reverse-engineer something, without much equipment... :devil:

    Your idea of multiple delay-triggers sounds like the best alternative. You may have to do some hand-alignment of the boundaries, depending on what the data looks like, and how accurate your delayed triggers are.
  6. Jan 20, 2009 #5
    yeah, you might want to add a delay timer, then play around with resolution until you see something significant. if it's really "weird", then it may be some kind of manchester encoding where you've got a sync bit at the beginning of a transfer. and this is confusing at first because, iirc, the sync looks like two bits but is over a three bit time period. once you figure out the encoding, you might want to look into buying a special purpose bus analyzer, which probably won't be cheap.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook