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  1. #1

    Question How to ensure reliable RS-232 connection?

    I have a configuration file for a network device(2100 lines). This device is configurable only over console line. If I copy chunks of those lines into terminal(I use minicom), there will be mistakes (sometimes some characters missing, space characters added etc). Hardware flow control and software flow control doesn't help either(as I use RS232-to-USB converter, I'm even not sure, if RTS and CTS signals are implemented). I tried with cu utility, but same issues appeared. There will be mistakes even if I copy in ~100 line parts. What causes those missing/added characters? Is there a terminal emulation program under Linux, which supports pausing before each byte/line transfer?

  2. #2
    Super Moderator Roxoff's Avatar
    Join Date
    Aug 2005
    Nottingham, England
    You're already using the best tool for this, minicom. Have you tried fiddling with the settings? I've not touched a serial port for years, but here's what I can suggest from memory.

    I'd guess that your baud rate is set correctly, but that you're using the wrong parity or stop bits count or, as you suggest, it could be flow control. If you don't have details of the connection speed, you could try patiently setting each manually and then testing.

    You may also find that the drivers for your USB-RS232 converter may be a little ropy. You could try on a real serial port (this could be difficult, I know).

    The other thing to look at is your RS232 cable. I remember, back in the day, having all kinds of connection problems with a home made cable. It could be that the hardware control lines aren't connected properly, so the data is seen but the CTX/RTX isn't being caught. Buying one from a shop really helped sort my issues out, iirc, but this was fifteen or more years ago.
    Linux user #126863 - see

  3. #3
    Linux Guru Rubberman's Avatar
    Join Date
    Apr 2009
    I can be found either 40 miles west of Chicago, in Chicago, or in a galaxy far, far away.
    If the speed, parity, and flow-control (hardware or software) is correct, then there should not be errors. However, if you are running 8 bits and no parity, then interference on the wire will cause this sort of problem, flow control notwithstanding. What are your port settings?
    Sometimes, real fast is almost as good as real time.
    Just remember, Semper Gumbi - always be flexible!

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