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ADC n DAC i should opt for minimum conversion time....

Discussion in 'General Electronics Discussion' started by ketanrd01, Sep 15, 2014.

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  1. ketanrd01

    ketanrd01

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    Aug 11, 2014
    Hi all!!!

    I wanted to know about ICs of certain components with minimum conversion time.

    The components include: 1. Flash/SAD type ADC (8 input and either 8/10 bit)
    2. R-2R DAC (either 8/10 bit)
    3. Demux

    would you please suggest me the ICs please....

    Thanks guys.....:)
     
  2. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Moved from PM:

    I don't have anything off the top of my head.
    How are you looking to interface with these devices? Are you looking to use a serial communication method?
    Also, how 'fast' are you looking. I can see what I can find.
    Directly to the Pi how?
    The Pi has no analogue IO. Are you planning to use the Digital IOs in parallel to communicate with your peripherals?
    There is also I2C, UART, and SPI.

    A direct connection could mean a few things.
    Well, electrically, the PI needs to communicate to the ADC and DAC somehow.

    There are multiple ways of doing so.
    Some ADCs will read an analogue value, and toggle the output of anywhere from 4-16 pins as the digital equivalent of what was read. This is inefficient, so communication is usually done with serial data.
    Regardless of the method used, the PI will still need to be instructed or configured to tell it how you connected the ADC and DAC.
    Telling it 'GPIO' is not good enough, as that is a generic balloon term to cover all of the available pins, and you need to specifically tell it what pins are used.
    The link I sent you above shows you what each GPIO pin does.

    Do you follow? Or is this still a little fuzzy?
    GPIO is not as easy as USB sadly, it's like telling someone to plug a device in the back of the PC without telling them if its USB, Serial, Parallel, PS/2, DVI, VGA, HDMI, etc.

    Im going to move this into the thread you started, and will continue there
     
  3. ketanrd01

    ketanrd01

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    Aug 11, 2014
    yep, planning to use digital IOs in parallel....
    I can specifically mention to which pins of R.Pi the digital output of ADC goes....and i still dont get what is the need for either I2C, UART, and SPI.
     
  4. ketanrd01

    ketanrd01

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    Aug 11, 2014
    Also, please tell me which ICs should i opt for.....
     
  5. Gryd3

    Gryd3

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    Jun 25, 2014
    Well. This is the list I am looking at so far : http://www.digikey.ca/product-search/en?FV=fff40027,fff80183,2640002,2640003,3cc0018,3cc0020,3cc0082,3cc008c,3cc009f,3cc00a0,a6c0006&k=adc&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=0&pbfree=0&rohs=0&quantity=&ptm=0&fid=0&pageSize=25

    If you want a 10-bit resolution, you will need at least 10 digital inputs on the RaspberryPi to convert parallel data to/from an ADC/DAC. (If you used one of the serial methods above, you could just use 2 pins to get all the data from a high resolution ADC/DAC) I have not yet gone through the list, as I am still unsure how fast you want it, you have not yet answered that question. Are you looking to make lots of samples a second, or to make a single sample?

    A little patience goes a long way. If you want to rush this, you can pick your own ADC using the selection tools from any of these suppliers : https://www.electronicspoint.com/resources/component-suppliers.34/
    Just fill out the list and tell it how many inputs/outputs, how fast, what kind of package, etc.
     
  6. ketanrd01

    ketanrd01

    74
    7
    Aug 11, 2014
    Yep, i have a R.pi B+ module and dont mind using 8/10 GPIOs for ADC. The reason why i dont want to opt for either I2C, UART, or SPI is that the pi is already quite worked up....

    As for speed, i want the conversion to be real quick since this data too is being sent via internet.. Also i am looking for more samples per second......
     
  7. ketanrd01

    ketanrd01

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    Aug 11, 2014
    Na i can wait....sorry for the impatience Gryd3 sir....
     
  8. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
  9. ketanrd01

    ketanrd01

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    Aug 11, 2014
    na, even something between 250k-2M would do...know any suitable IC?
     
  10. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Something like this http://www.digikey.ca/product-detail/en/MAX155BCPI+/MAX155BCPI+-ND/1701469
    Meets your requirements that you have listed. Flash or SAR.
    8-input, 8-bit. 250k samples per sec.
    Other packages are available here : http://www.digikey.ca/product-searc...ee=0&rohs=0&quantity=&ptm=0&fid=0&pageSize=25

    Of course, you should really try out one of these selection tools :
    http://www.digikey.ca/product-searc...tion-analog-to-digital-converters-adc/2556291

    Just go through the lists and select what you want and hit apply. You can slowly filter the massive list down, then sort by price to get a cost effective solution.

    250k samples is quite high.. what are you trying to track/transmit?
     
  11. ketanrd01

    ketanrd01

    74
    7
    Aug 11, 2014
    I am giving 8 inputs to the ADC.....5 inputs from 5 flex sensors,1 from encoder and 2 from accelerometer.
    Thanks for the information Gryd3....
     
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