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interfacing 8051 with adc

Discussion in 'Electronic Design' started by gautham, Jan 9, 2007.

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  1. gautham

    gautham Guest

    hi,i am working project where i have interface a microcontroller with
    an adc & an rf transceiver.what are the steps that i have to take to
    interface the
    microcontroller with the adc and the rf transmitter?i am planning to
    use an atmel product.what series would be best for my
    project?microcontrollers with inbuilt ADC'S are also fine.
     
  2. mkaras

    mkaras Guest

    You probably need to be a lot more specific as to what your project is
    going to be,
    what your intending to sample with the ADC, resolution you hope to
    attain and the
    sample rate that will be required. On the RF side we have no idea what
    you think the
    RF would be expected to be for. For all we know you hope to have the
    microcontroller
    enter into communications with your microwave oven.

    - mkaras
     
  3. Ken Smith

    Ken Smith Guest

    If about 8 bits is good enough, look at www.cygnal.com and pick the one
    that does what you need. Beware that because they are on the same ship as
    the micro, they are noisy.

    If you need better, go to www.linear.com and look at the ADCs they offer.
    Some interface like external memory and others use a serial connection.
    For the serial ones, you need to step through the timing diagram with
    code. Fortunately, in the 8051 this is very easy to do.
     
  4. Guest

    Hey Gautham,

    Please be more specific. I see that you want to interface an ADC. But
    unless you are completely aware of the signal characteristics you want
    to digitize, it would be extremely difficult to comment on the design
    part of it.

    It is my understanding that you want to convert the Analog data and
    transmit it through some RF transceiver

    Well first find out the signal data characteristics. Determine the
    resolution required. It is quite possible that the Microcontroller you
    choose may have an inbuilt ADC (on chip). If you need a higher
    resolution, you may have to use some other ADC.

    About the RF part, you have find out the characteristics of the
    Transceiver then determine how you have to design that part of the
    interface.

    Good luck in your design.
    Bye
     
  5. Eeyore

    Eeyore Guest

    Have you previously used a microcontroller's data bus to interface to any other
    devices ?

    Graham
     
  6. SFC

    SFC Guest

    avr are easy to use/program.

    SFC
     
  7. gautham

    gautham Guest

    well,to be more specific,the data input to the microcontroller comes
    from a 220v, 50Hz power line,representing the power flow,voltage
    etc.this analog data is interfaced with the microcontroller with an
    adc.the frequency of the signal being less,any frequency on the upward
    of 1MHz would work very fine.the resolution that i want is in the order
    of a few hundred millivolt.therefore,i am planning to use a 14 bit
    adc.my question is regarding the hardware interfacing of this adc with
    the microcontroller. for example,how do i tune the microcontroller to
    the frequency of the adc?would the results be accurate?the rf segment
    is to connect the microcontrolller wireless to a remote host computer,
    where detailed analysis of the data would be done.
     
  8. gautham

    gautham Guest

    i have worked on a robotics project, where i interfaced the
    microcontroller with an ir sensor module and a motor module(to run the
    bot).my doubt is mostly in the hardware interfacing of the
    microcontroller.the signal frequency is 50Hz,and i plan to use a 14 bit
    adc.how do i synchronise the adc with the microcontroller? would a
    simple timer routine(software) suffice?i also don't know as to how to
    set a constant supply voltage to the adc ?(because resolution of the
    adc is highly sensitive to the supply voltage).also would the AT89c51
    series of atmel provide the solution?or is a better version required?
     
  9. Eeyore

    Eeyore Guest

    Synchronise ? Do you mean 'handshake' ?

    The question is impossible to answer without knowing the ADC. You probably need to
    send a start conversion signal and monitor it for a conversion completed signal.

    This is basci microcontroller stuff.

    The 89C51 is just a common 8051 family variant. Nothing special there !

    Graham
     
  10. Eeyore

    Eeyore Guest

    What's that got to do with interfacing ?

    Graham
     
  11. Eeyore

    Eeyore Guest

    You don't.
    How much microcontroller experience do you have ?

    Graham
     
  12. Guest


    Hi Gautham, Now in most of the microcontrollers, you sure to find not
    one, but two or three ADCs with average of 14 to 16 bit resolution.
    Have a look at this report where latest microcontrollers are listed
    with some specs. Here is the link
    http://www.emittsol.com/section/market-analysis/ma100001.html
    EMITT Solutions also can provide a list of RF trasceivers provided you
    give exact specifications.
    Check with www.freescale.com, in case you need short range RF
    transceivers.

    Atmel is fine for 8051 based MCUs. If your MCU need to handle more of
    Audio and Video than go for RISC based.

    Srinivasa Reddy N.
    EMITT Solutions
     
  13. Guest


    Hi Gowtham,

    Let me get this correctly. You actually want to connect the 220V 50 Hz
    mains (AC) to the ADC and digitize it. Is that what you want to do?(pl
    confirm)

    Well, I have not come across an application like that. But I dont think
    there is a ADC which can directly accept that kind of voltage (220v).

    There should be some kind of scaling system in between. If that becomes
    the case, I dont see how a 14 bit ADC will help. The margin of error
    may be quite large (due to scaling sys).


    Regards.
     
  14. Guest

     
  15. Nico Coesel

    Nico Coesel Guest

    I recommend staying away from any 8051 controller. There are much
    better (faster and easier to program) microcontrollers available. Like
    the LPC2000 series from NXP, the MSP430 / MSP470 from Texas
    Instruments, etc, etc.
     
  16. The first step is to select an ADC that suits your task, and is easy
    to interface. I've used ADCs and DACs that communicate with the 8051
    using SPI bus. I did the SPI communications using "manual
    bit-banging", but there may be some 8051 (or other micro) versions
    with a SPI interface.

    Depending on the accuracy you need, you may want a voltage reference
    IC to provide the reference voltage for the ADC - but some ADCs have
    an internal reference.
     
  17. Rich Grise

    Rich Grise Guest

    Something prompted me to bother to go and look up the MSP430 data sheet,
    and looking at the architecture and register set made me drool. ;-)

    No, not because I'm an imbecile, but because it reminded me of the
    PDP-11 and IMP-16. Looks like a neat processor. ;-)

    Cheers!
    Rich
     
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