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Re: Assist human unobtrusively in a 3rd party Windows GUI

by jmlynesjr (Deacon)
on Dec 13, 2020 at 00:22 UTC ( #11125084=note: print w/replies, xml ) Need Help??


in reply to Assist human unobtrusively in a 3rd party Windows GUI

It's a shame that your vendors didn't implement a serial protocol that would automatically restart and resync. A serial implementation of IBM's Bisync protocol works nicely.

James

There's never enough time to do it right, but always enough time to do it over...

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Re^2: Assist human unobtrusively in a 3rd party Windows GUI
by Marshall (Canon) on Dec 13, 2020 at 00:51 UTC
    The protocols run at 38400 baud which is as fast as RS-232 serial can go.
    There is no idea of a "connection" or a "packet of information".
    A multi-byte command is sent and then a multi-byte response is expected.
    There are many ways for this to go wrong!
    When the response is "nonsense" (including some time out values), a RESET is required.

    The typical serial device does not implement any kind of idea a "connection".

      Actually the RS-232 standard doesn't specify bit rates at all, although it does suggest bit rates above 20,000 aren't supported. I routinely use a baud rate just below 1e6 Baud for a debug port on embedded systems I'm working on. That connects using a FTDI serial to USB cable. It would commonly be called RS-232, even though no part of the system bears any relationship to the RS-232 standard which is all about plugs and signalling levels.

      To my way of thinking a serial cable between two devices is essentially the definition of a "connection", although that has become a much abused word in this context, rather like RS-232 actually.

      Optimising for fewest key strokes only makes sense transmitting to Pluto or beyond

      Are you receiving a checksum or CRC-16? If not, how do you know that any message is received correctly?

      Are you connecting via modems? At higher bit rates cable lengths become a problem. It's very difficult to make these open-ended systems operate reliably. Do you have any capability to run any loop-back tests on your circuits?

      James

      There's never enough time to do it right, but always enough time to do it over...

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