Help on DA system needed please

Discussion in 'The Projects Forum' started by yeezhihao, Sep 30, 2007.

  1. yeezhihao

    Thread Starter Member

    Sep 30, 2007
    11
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    hi

    i have a data acquization HW in place, consisting of op-amps and filters.

    What i would like to do now is pass this output to an ADC(successive approximation) which would output the 8 or 10 bits into a Parallel to serial shift register.

    This shift register will then push out the bits serially and i intend to send these bits to a blue tooth module so tat it will send the data to PC or mobile phone eventually.

    Question:
    1. Is my above idea realistic?
    2. Is it possible to achieve the above without any microController? Cause what i perceive here is that no microcontroller is needed as the ADC simply converts and pass it to shift register...Or is microcontroller needed to tell ADC when to sample, how fast to sample etc etc??
    3. Is there a need for serial interface like Max-232?? Why is there a need for 232? can't i just use the shift register and send the bits to the bluetooth module?

    I also understand that shift register requires clock to move the bits, and since my proposal is without a microcontroller, i was thinking of using clock generator to clock the register? Am sure there are such products in the market right? Or am i wrong to say so??

    I really dun wanna use a microController cause its gg to add to the size and power consumption of my system, which is suppose to be portable.

    Your comments on this matter please.

    Thank you very much!
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Sure, why not?

    You can get IC's that combine those functions.

    Take a look at Maxim's MAX7651/MAX7652 family. Dual 12-bit ADC with serial and parallel outputs. Uses an 8051 processor core. Perhaps that's a bit overkill for what you're trying to do, but such IC's do exist.
     
  3. yeezhihao

    Thread Starter Member

    Sep 30, 2007
    11
    0
    Hey! thanks for the prompt reply...

    hmmm...was actually wondering if it would be totally possible to control these chips without any microcontroller...

    since u mentioned about the Maxim range, it still has an in built MCU.
    What i want is to reduce cost and complexity as well, no MCU at all....just an ADC, shift register and maybe a serial interface to hook it up with bluetooth...

    is it possible to built such a DA system with these simple components and controlled by some simple logic gates??
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,136
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    Possible - yes. Practical - probably not. As soon as you move from raw data to protocol it will become impractical without a microcontroller.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Yep, what Papabravo said.

    It COULD be built with "simple components" and "simple logic gages".

    That's the way it used to be done.

    But when you can obtain programmable microcontroller IC's like the PICAXE, nearly the cost of a single "simple component" IC, why would you want to go to that extra trouble and expense?
     
  6. yeezhihao

    Thread Starter Member

    Sep 30, 2007
    11
    0
    thnx agian 4 ur prompt reply...
    ok, i'll try to explore using MCU, but wld like to ask a v basic que, the pins on the MCU are not like the regular IC pins, how can i get them to be fixed onto my test breadboard?? sorry if this sounds a little dumb but this simple que has been bugging me for quite a while...

    also another reason why i'm trying to avoid MCU is i really have fear in Assembly...setting the timers for sampling, reading it frm ADC, interrupts, ports....gives me shivers...

    think i'm too use to using simple component ICs to get things done...guess i'll have to change my mindset tat a MCU isn't really that complex afterall
     
  7. yeezhihao

    Thread Starter Member

    Sep 30, 2007
    11
    0
    yes i fully agree with u...i ever did a really really simple calculator using FPGA...it was hell! way too too tedious...but it was a really great experience..

    anyway,coming back to my case, i dun think my operations are that complicated, so thats why i thought of using gates to control the logic...cause i believe many instructions can be achieved via a clock generator and playing with its pulse width....

    btw, lets say i managed to handle the protocols w/o a MCU, can i ask wat is the purpose of having a serial interface or rather is there a need for having a serial interface like (old ACIA or max232) when i already have a shift register that pumps out individual bits?
     
  8. Distort10n

    Active Member

    Dec 25, 2006
    429
    1
    TI has the MSC family which is a 8501 ADC/DAC combo.
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Funny, the Maxim family I suggested in the first reply suggested nearly the same thing ;)

    Yeezhihao, I can only presume (assume) by your name and your atrocious (very bad) spelling that English is not your primary (first) language. That may make things more difficult - although I can assure (give you certainty) you that I would be COMPLETELY lost in trying to communicate in YOUR language! ;) While you are here, it would help/assist communications if you will try hard to spell things out instead of using Internet-style "shorthand" or abbreviated (short hand) spelling. People will take you more seriously; if that is important to you.

    Assembly-type language is intimidating (fearful, frightening) only at first. Within a month or so, you will begin to discover how powerful it is. After that, you will never want to return to "the dark days" of being forced to accept only what was offered/featured in a single integrated circuit.

    Empower yourself (give yourself the power) and learn the programming language. In reality it is not difficult (hard) to learn.

    You will be ready for much more complex problems if you master even one single microcontroller.
     
  10. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    Microcontrollers and assembly language both are well worth your time and effort to learn. Microcontrollers open up many design paths that would otherwise be difficult to implement. Add to this the flexibility to quickly alter your design to cope with a design change and you have a recipe for success not to mention fun.

    Learn to design with and program micros and you are likely never to regret it.

    hgmjr
     
  11. yeezhihao

    Thread Starter Member

    Sep 30, 2007
    11
    0
    I'm so sorry that you found difficulty in comprehending my posts.
    I should have realized earlier that I'm not speaking to someone from my own country. Will be extra careful from now onwards.

    Yes, I will also avoid using any short-hand and try to make myself as clear as possible.

    Please allow me to repeat my question once more:

    I would like to know how can I connect a MCU (eg: from TI) to a breadboard for testing purposes as these MCUs have pins which are much "finer" than the ones which you would usually find on a simple IC component.

    Please do not tell me that the only solution is to solder the pins individually to the required wires? That would sound like a really tedious and slow process!

    Another question.
    If i were to purchase an MCU, do they come with any development programs for me to write my asm and download them to the MCU? Do I have to built a separate serial interface to download my program to the MCU? Where to find the compilers and linkers for the MCU?

    Please enlighten.
    Thank you.
     
  12. yeezhihao

    Thread Starter Member

    Sep 30, 2007
    11
    0
    Hey Sgt!

    Thanks for the heads up. Did a google of PicAxe and it seems like a great low cost MCU. Its simple to understand, the programs are easy to write and most importantly, it serves my needs well without the extra complexity.

    However, I had some difficulty in searching for the detailed data sheet of the PICAXE. All of them seem to be very brief.

    I'm trying to find out information like whether a SampleHold circuit is embedded within the MCU and how can I go about selecting the sampling frequency. In addition, would like to know whether the sampling frequency of PicaAxe is high enough(to meet nyquist frequency) to prevent aliasing.

    Would you happen to know where I could find these detailed information on PicaAxe.

    Thanks once again!

    Cheers!
     
  13. Distort10n

    Active Member

    Dec 25, 2006
    429
    1
    I am assuming you are alluding to surface mount packages like a QFN, SOIC, LCCC, or a BGA...although I could not imagine a microcontroller in a BGA type of package. You have several choices:

    1. ZIF socket for a specific type of surface mount package. The MSP430 from TI should still have their own development board with a ZIF socket. Other manufacturer's may as well.
    2. Design your own PCB board with the component.
    3. You could also solder a surface mount part to a DIP adapter, but you are still soldering. These would be impractical for large pinout microcontrollers.


    TI's MSP430
    Atmel's AVR
    Microchip's PIC

    All of these have development tools: boards, software, interface.


    Most modern ADC's have a sample and hold integrated into the silicon. This also means that ADC's integrated into devices like a DSP, microcontroller, or CODEC will have a sample and hold.

    To answer you on selecting the sampling frequency it would be a register you would have to write a value to in your code.
     
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