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Basic A/D question (newbie looking for help)

  1. Oct 16, 2006 #1
    i'm a software guy trying to solve a little A/D problem i have...

    i hve a daq that has a small number of I/O's and i have an A/D that i need to get data from. is there a chip in existence that can stream over one data line? my idea was to use one line to use as the data stream and the other line to step through the A/D value.

    so if the output is 110101 i could change the state of a control line and when that state changes, the bit stream line would represent the next bit.

    does this exist? and if so how does it work... does the control line listen for just a state change or only when it goes from low to high

    thanks everyone in advnace!!
  2. jcsd
  3. Oct 16, 2006 #2


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    Staff: Mentor

    I'm not real clear on what you would like to do. It sounds like you have a DIO card for your PC with some number of digital IOs, and an A/D converter card also. And maybe a DAC card with an analog output capability too? Or is the ADC a discrete chip or board that you need to acquire data from to get it into your PC? And maybe your ADC chip has a parallel output that you want to serialize for some reason to get it into your PC via some DIO lines?

    Maybe try painting the picture again so that we can help you understand your options.
  4. Oct 16, 2006 #3
    what i have is a single board computer running linux. this is for an embedded systems application. the board has 8 I/Os on it and i need to use them sparingly i can hook up all 8 i/os to the A/D since i need to run 2 of them as well as a few other things...

    so i was thinking use 2 data lines per A/D.. one as a control line and one as a data stream line..

    any help is appreciated
  5. Oct 16, 2006 #4


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    Staff: Mentor

    What are the A/Ds? Do they have a serial interface mode like SPI or I2C? If they are only parallel (how wide? what interface?), then you might be able to use an SPI or I2C serial-to-parallel IO expander of some type to do what you want.
  6. Oct 17, 2006 #5


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    Staff Emeritus
    Science Advisor
    Gold Member

    There are many low-cost ADCs which use I2C (a two-wire protocol) and SPI (generally a three-wire protocol).

    Look into, for example, the AD7476, AD7477, and AD7478. If you want more specific suggestions, you will need to tell us some of following information about your application:

    What sampling frequency, bandwidth, or accuracy (effective bits) do you need? Are there any power requirements? What voltages are you intending to sample? How fast can you toggle or read your I/O lines?

    - Warren
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