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PC Printer Port Controls Data Logger

Discussion in 'Electronic Design' started by Animesh Maurya, Apr 27, 2004.

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  1. Hi all,

    http://www.maxim-ic.com/appnotes.cfm/appnote_number/142

    Please see the above link, a PC printer port data logger system, built
    around with MAX132 (±18-Bit ADC with Serial Interface).

    I am very keen to have such a data logger for my project work,
    but over there it is written that data acquisition rate is 1data/sec,
    which is quite slow to work with.

    I don't know whether it is a software limitation or a hardware one,
    which freezes it to 1data/sec.

    But if this is hardware one, how can I increase the data capturing
    rate up to 1data/msecs.

    Finally if all above said cannot be done, someone please suggest a
    appropriate link to have some other data logger.

    Any help is strongly appreciated.

    Thank you

    Best regards,
    Animesh Maurya
     
  2. budgie

    budgie Guest

    If you don't really need an 18-bit ADC but can surviuve with 12-bit (that's 0 to
    4095 unipolar) and eight channels, with four binary outputs, have a look at

    http://www.kitsrus.com/kits.html#k118
     
  3. Bob Masta

    Bob Masta Guest


    I have not studied this circuit carefully, but I've
    used similar serial ADCs before. The ones I've
    used were 12 bit (LTC1285), and the problem
    is that you are trying to send serial data over a
    parallel port, where your software has to take care
    of all the handshaking. For each and every bit
    of each data conversion, you have to do a complete
    handshake, which means a *lot* of I/O traffic.
    In pure assembly language I was able to nurse
    the LTC1285 up to about 15 kHz overall sample
    rate for a single channel, but that was about the limit.
    If you also have to send channel control signals,
    as well as trasnfer additional bits, your top speed
    will be less. Don't know about the Maxim chip,
    but on the LTC it was possible to reduce resolution
    by simply not reading the LSBs and get a speed
    increase.

    All things considered, I'd guess you could expect
    at least a few thousand samples per second.
    Note that this is not especially dependent upon
    CPU speed, since the I/O bus cycles are around
    1 usec each and I don't think that faster systems
    run the port I/O any faster than that. However,
    if you are writing in a high-level language instead
    of assembly, then the CPU speed might make a
    difference in burning through all the high-level
    deadwood.

    Also note that this will require DOS in order to get
    direct access to the I/O ports, which means you
    can't do this in WinNT, 2K, or XP. However, there
    are generic I/O drivers available for these that are
    supposed to give you access to the ports. I haven't
    tried these. One name that comes to mind is GIVEIO.
    Check out Jan Axelson's site <www.lvr.com> for more
    info on these drivers, as well as all sorts of port info.

    Hope this helps!



    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
     
  4. .....
    Also consider the settling time when switching channels (for the port to
    settle).
    If you are after a single stream things can happen alot faster.
     
  5. When using a par port input you need to consider the task switching
    and interrupt times of the operating system.
    We are talking milliseconds here.
    It could be done, but you would have to buffer first in hardware after
    the AD.
    I do not know if that MAX 132 has somne build in buffering.
    Any micro controller with some RAM (internal or external) would do.
    So, you would have to read say samples from the buffer with the PC
    until that buffer is empty, the micro would do the timing.
    JP
     
  6. Thanks all for those nifty ideas.

    This time I was looking for cooked food, I have to do a lot of reading
    work before implementing any for yours above thought.

    Thanks for your time

    Regards,
    Animesh Maurya
     
  7. Soeren

    Soeren Guest

    Hi Animesh,
    Nope, 15 bits (or ±14 bits if you will).

    That depends on what you are doing.
    HAve you considered one of the (freeware) oscilloscopes (some with FFT-
    analysis as well), which utilizes your sound card for the A/D ?

    <URL:http://polly.phys.msu.su/~zeld/osc251.zip> is one.
     
  8. Bob Masta

    Bob Masta Guest


    One additional thought: You might want to check out
    the Dataq "starter" system. It's under US$30 and
    comes with a demo of their Windows software. Plugs into a
    serial port and acquires 4 channels at a few hundred
    samples per second. Or at least the ones they were giving
    away free did, a few years ago. They might be even
    faster now. At the time, the only option was to use their
    software, but I think there was a lot of user interest in
    developing other applications. I'd recommend checking
    the Dataq site to find out about the model number and specs,
    then Googling for what others might have done with it.

    Just a thought....



    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
     
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