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EIA RS232C serial comm — Parallax Forums

EIA RS232C serial comm

nick bernardnick bernard Posts: 329
edited 2005-01-27 19:55 in BASIC Stamp
Does anyone have any experience with EIA RS232C ?
i'm considering a nifty new application for my stamp that requires this protocol (an HG2F by IDEC)
i found a link via the legendary google for the basics
http://www.science.uva.nl/faculteit/museum/rs232c.html

but if anyone has any specific advice it would be well recieved.

ROX ON

nick bernard

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League Bowling.... it's not a sport, it's a way of life

Post Edited (nick bernard) : 1/27/2005 7:58:33 PM GMT

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2005-01-27 16:24
    Sure, lots of people have experience with EIA RS-232c, that's what SERIN and SEROUT support. Note that the 'full' specification details a lot of hand-shake signals which may or may not be supported.

    The problem with this 'standard' is that there are so many slightly different implementations of it. Three-wire (TX, RX, and GND), five-wire (add RTS and CTS), eight-wire (add DTR, DSR, DCD). DB-25 (the original) DB-9 (IBM's version) RJ-45 (DEC's version). How it's used with a Modem (the original use). How it's used with a Printer (what IS the 'paper out' signal anyway? Usually DTR)

    THEN, people implement additional byte-oriented protocols on top of this. Sync characters, checksum characters, is it ASCII encoded? or binary? Message Count fields. MODBUS uses some variation, I understand. Oh, and I almost forgot the byte encoding -- 8 data bits, No parity, 1 stop bit? 7-data bits Even Parity? 2 stop bits? And of course there's baud rates. 300, 1200, 2400, 9600, 19200?

    THEN, the spec says +-12 volt signalling, or +- 10 volt, or +- 5 volt. Some people signal at 0 to 5 volts.

    The amazing thing is, the BS2 provides enough flexibility (with a MAX232 for level shifting here and there) to cope with most of this.
  • allanlane5allanlane5 Posts: 3,815
    edited 2005-01-27 16:31
    http://www.idec.com/Products/ENG/PDF/annoucements_all/HG2F.pdf

    Hmm, dude, if this is what you're trying to interface, it looks like it was designed to control or be controlled by PLC platforms. This is not a show-stopper, but I'm not sure what resources the controlling processor has to have. It looks like the 26 bytes on the BS2 might be not enough to do the job.

    You'll need the manual to find out what byte-level protocol it implements with the PLC's, to know if the BS2 can handle it. The HG2F looks like a really cool device though -- a small (8"? 4"?) touch-screen serial terminal with graphic display.
  • nick bernardnick bernard Posts: 329
    edited 2005-01-27 19:55
    thx guys
    i assumed EIA RS-232c was a specific flavor of rs232 with specific parameters such as baud, voltage levels, encoding, and flow control. but i was wrong. i am now comfortable enough with my emotions to admit that (thats a little joke there....)

    http://www.brod.dk/products/hmi/idec/displays/main/manuals/hg234f.pdf
    page 7 mentions DM Link communication and states that the screen can be controled by non plc-host devices
    page 16 has some protocol info

    i have my idec sales rep looking into the sentence structure for me. I think that will be the determining factor. i have some bs2p's and javelin's to work with. I should stop starting all my sentences with 'I'.

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    League Bowling.... it's not a sport, it's a way of life
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