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ps/2 port on a pc

Discussion in 'Electronic Basics' started by Randy Day, Aug 24, 2013.

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  1. Randy Day

    Randy Day Guest

    I have an old DOS (yes, DOS) laptop that I want
    to use in a project. I want to have two-way
    communication, but the ONLY port this thing has
    is a ps/2 port.

    I can find lots of info on sending chars TO the
    PC, but I can't find anything on sending
    characters OUT the port to my micro. Is there a
    register I can POKE, an interrupt I need to call?

    I have QBasic on the laptop, so I can PEEK and
    POKE as necessary.

    Any advice is greatly appreciated.
     
  2. Jasen Betts

    Jasen Betts Guest

    the port doesn't communicate in characters it commnicates in bytes,
    if you haven't got a copy of RBIL yet, get one.

    IIRC this is covered in PORTS.TXT
    There were things you could do on some keyboards that would crash
    GW-BASIC, I don't recall if QBASIC was also succeptible,


    It it possible you will need to write an ISR, so youd'd need something
    stronger. I know "Turbo C 2.0" is a free download from Embacadero after
    registration. or DJGPP if you have a 386
     
  3. Randy Day

    Randy Day Guest

    I've seen any number of sites that say you CAN
    send characters, and that describe the protocol
    for communicating, but none of them talk about
    the how-to's from the pc side.
    Believe it or not, this laptop only has one
    i/o port: the ps/2 port. No serial, no lpt.

    I will do some searching on the blinking
    lights thing, though. Thanks.
     
  4. Randy Day

    Randy Day Guest

    [snip]
    Oo! Interesting! There is indeed a
    section on the 804x keyboard controller.

    I'd be ecstatic if all I had to do was
    check a status bit, drop a byte into
    60h, and have the controller handle the
    actual signalling. Can it really be that
    simple? Time to fire up the 'scope!
    If it is, I'm sure I'll find out! ;)
     
  5. Jasen Betts

    Jasen Betts Guest

    That's sounds about right, it's been 20 years.
     
  6. What kind of laptop has no serial port or parallel port, or PCMCIA slot
    for such an interface?

    For that matter, what kind of laptop doesn't have any of that, but has a
    PS/2 port? The PS/2 port is used for a keyboard, and I can't think of any
    laptop from back then that had the port for an external keyboard, that
    sort of thing came only when USB started becomiing the norm. Or PS/2 is
    used for connecting a mouse, but a DOS laptop isn't likely to have much
    use for a mouse to have the port, and before mice were standard, often
    other interfaces were used (like serial port, and a card the expansion
    bus).

    It seems most likely you think you have a ps/2 port but likely it's
    something else.

    If the laptop has a parallel port, back then the parallel port was
    generally one way, except it had a bunch of status lines to read from the
    printer, so one could do an odd two-way communcation through a parallel
    port, there was a whole "standard" for this. If it's serial, then you
    just communicate over it, everything's in place.

    Michael
     
  7. whit3rd

    whit3rd Guest

    Probably a contracted model that just acts a a terminal to a
    bar-code scanner. That kind of setup was pretty common for a
    few years, for inventory and warehouse folk to hang on their necks.
     
  8. Randy Day

    Randy Day Guest

    It does have 2 pcmcia slots, but I'm not
    going to spend money on cards or time on
    finding drivers. The port only has to
    transmit a few command bytes to the micro
    once in a while, so emulating a kbd is more
    than adequate.
    The brand may give you a clue to its age: "Digital".

    The port does work with an external keyboard, and
    there's a mouse symbol as well as a kbd symbol next
    to it, so I assume it can do double duty.
    No, it works with a keyboard. The machine does have
    an integrated trackball, but I've never tried to
    test that.

    Now, *maybe* the unit ran an early version of
    Windows, but it's got DOS loaded, and even
    navigating menus in QBasic shows some lag, so I
    don't think it was a speed demon even in its day.

    However, the display (320x240!) is flawless, and
    the unit does a mean spreadsheet, so I'd like to
    repurpose it; it'd make a good console for a
    logic analyzer or other uC project.
     
  9. Jasen Betts

    Jasen Betts Guest

    barcode scanner could be RS-232 or PS/2,
     
  10. Jasen Betts

    Jasen Betts Guest

    With the right a splitter cable you you should be able to attach both
    simultaneously.
    What CPU? if it's got ps/2 mouse I'd expect at-least 80286
     
  11. Found RBIL no problem but not PORTS.TXT.
    Suppose this document covers the problem as well,
    http://www.computer-engineering.org/ps2keyboard/
    though I like to find PORTS.TXT as well.

    petrus bitbyter
     
  12. Randy Day

    Randy Day Guest

    [snip]
    The doc I used was PORTS.A in Inter61D.zip.
     
  13. Randy Day

    Randy Day Guest

    [snip]
    According to the interwebs, it has a 486DX2/50.

    Maybe the fact that it has a 'government salvage'
    sticker on the back means it picked up a few bad
    habits working for the government! <g>
     
  14. Found thanks.

    petrus bitbyter
     
  15. T

    T Guest

    I've got a magnetic card reader/writer. I have an old Inspiron 4100 that
    I have to use with it since it has both the PS2 plug and a real serial
    port.

    All the PS2 connector does is supply the 5V current for the thing. The
    serial port is where the action happens.
     
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