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DAC software

Discussion in 'Electronic Design' started by DL, Apr 2, 2008.

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  1. DL

    DL Guest

    Hi,

    I would like to incorporate a DAC in a board design so as to provide
    some biases in the rest of the circuit and was wondering if anyone
    knows if any company provides software that could program their DAC
    through the serial or parallel port. Unfortunately, there is not much
    time for designing and testing so I don't have time to write the
    program myself. There are no tight specifications on the DAC
    (preferably running at 3.3V and accuracies of 10bits and up are fine)
    so basically any DAC will do as long as it has ready software to
    program it.

    Thanks in advance for any suggestions.
     
  2. nyboard

    nyboard Guest

    Hi, I guess you need to look for the sample program from the
    microprocessor datasheep or application note. If you are using PIC,
    perhaps you can find the program from the microchip website or just
    google it. Good luck!
     
  3. DL

    DL Guest

    Sorry, I forgot to mention that I meant discrete DACs rather than
    embedded into a microprocessor. Ideally I would like 8 of them in one
    package. LTC and Analog Devices have some but the software they
    provide is meant only for their evaluation kit.
     
  4. Guest

    The fact products get designed and sold with such a lackadaisical
    attitude is mind boggling. I expect this in software, but not
    hardware.

    Personally, this sounds like an application for those digital
    potentiometers made by Microchip and others. Also, 10 bits for bias
    sounds excessive. If trim is being done, you get close with resistors
    then tweak with the pot.
     
  5. DL

    DL Guest

    Joel is partly right. I indeed am a hardware design guy, but there is
    nobody else who will do the software. So it should be either available
    by the company that makes the DACs or I have to write it on my own.

    I have programmed in the past similar devices (e.g. ADCs) and one can
    directly program them using a computer and the parallel or serial
    port. The program can be written in any language and is easy in its
    concept. The problem is that I don't have time much time and that's
    why I was wondering if there is a ready solution.

    [email protected] you are right. A 10bit accuracy is not needed but 10bit (or
    actually 8bit) is the lowest you can find available anyways for a DAC.
    Using pots to tweak the bias values has the problem of drifting and
    adjustment is needed every once in a while. DACs don't have this
    problem and if ones with memory are used, then they just need to be
    programmed once and not every time the power is turned on. Another
    aspect is that I need 8 biases and therefore an octal DAC will use
    much less space than 8 pots.

    So basically my question in the post was if anyone has used or knows
    of a simple program that runs on a PC and uses parallel or serial
    interface and that can directly provide the right sequence of signals
    for a DAC to be programmed. A microprocessor or microcontroller is not
    needed.

    Any help will be greatly appreciated.
     
  6. Rich Grise

    Rich Grise Guest

    "Program" a DAC??? Why not just get one with a parallel interface and
    write to the silly thing? For example, one I remember from cave-man days
    is the MC1488, which just has 8 input pins, and when you write your
    data to it (via a latch, probably), it just puts out the corresponding
    current, which can be converted to a voltage with a resistor.

    Good Luck!
    Rich
     
  7. Rich Grise

    Rich Grise Guest

    It sounds like f'in homework, is what it sounds like.

    Thanks,
    Rich
     
  8. Rich Grise

    Rich Grise Guest

    .
    There is no program needed. No program at all, other than the ability
    to output an 8-bit byte out the parallel port. And latch it, of course,
    but that's hardware.

    Latch the byte, and give it to any ordinary 8-bit DAC - Digi-Key has
    hundreds, if not thousands, of them to pick from. Output the byte
    through the port, latch it, let the converter convert it, and you're
    done!

    And don't top-post.

    Good Luck!
    Rich
     
  9. Rich Grise wrote:

    Bit banging into the serial DAC from the parallel port is very simple also.
    That was in the old good cave man days. In our days, you will need a
    kernel level driver to access the PC parallel port directly. BTW, there
    could very well be no such thing as the parallel port at all :)



    Vladimir Vassilevsky
    DSP and Mixed Signal Design Consultant
    http://www.abvolt.com
     
  10. Guest

    Actually, I suggested digital potentiometers, not a real trim pot. The
    nice thing is they have eeprom, so once "trimmed", they wake up in the
    right state (value). I don't know what your project is, but some
    system designers like the box to stabilize before tweaking. So they
    wake up in the last state, then once running a while the user is
    requested if they want higher accuracy.

    Here is some random hit:
    http://ww1.microchip.com/downloads/en/DeviceDoc/22017a.pdf

    By no means is the market limited to microchip.
     
  11. Guest

    Modern OSs like to own the hardware, which makes hacking difficult.

    I'll leave the company name out of it, but we did a bit banging
    solution using the dos found on the windows boot disk. I thought it
    was cheesy, but not a particularly bad idea. Somehow a virus got on
    the boot disks we gave to customers. At that point I thought it was a
    bad idea. ;-)
     
  12. For that reason, I keep the 12-year old computer with Win98 as an OS.
    Win95/98/ME allows the direct access to ports with the interrupts disabled.

    There are the special drivers for the port hacking in WinNT/2k/XP
    (dllportio and such). It works, however the timing jitter is horrible.

    I don't know if there are the drivers like that for Vista. I am not
    familiar with Vista internal architecture, however somebody told me that
    it is very difficult to patch the I/O map there.
    Finding a floppy drive is a problem in our days. Booting MSDOS from DVD
    would be fun though. :)



    Vladimir Vassilevsky
    DSP and Mixed Signal Design Consultant
    http://www.abvolt.com
     
  13. http://www.freedos.org/freedos/files/
    I have tried it, but not sure I did a direct boot,
    maybe I only tried the virtualizer.
    Still have the CDROM, been some time.
     
  14. Didi

    Didi Guest

    LOL, I as wondering what was wrong with Richs numbering - he clearly
    meant the Motorola designation of DAC08, at least this is how I read
    it
    in the context.
    I had to see your post to think on the 1488/9 (good old
    friends) ... :).
    I believe (15+ years old memory) DAC08 was called MC1408, have not
    used
    one in a while (but until not so long ago their multiplying ability
    was
    among the best in the class, now they got outclassed, eventually...).

    Dimiter
     
  15. Rich Grise

    Rich Grise Guest

    Yeah - I realized that when I looked up the data sheet. The one I
    shouild have been thinking about was MC1408L8, but apparently for
    8-bit parallel input these days, the DAC08 is the chip of choice.

    In fact, I should have known that - the 1489 is the mating receiver, for
    something much like "RS-232"; at one company, my engineer and I were
    looking at them for a serial link, but we decided they weren't robust
    enough to go on a ship, (as in navy battle cruiser or so), so we designed
    the interface(s) with discretes - JANTX2N2222As and JANTX2N2907As. :-}

    You could plug those puppies into the wall socket and not blow them up!
    ;-)

    Thanks!
    Rich
     
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