Looking for that perfect microcontroller

Discussion in 'Embedded Systems and Microcontrollers' started by sjkim0329, Dec 16, 2008.

  1. sjkim0329

    Thread Starter Member

    Oct 19, 2008
    12
    0
    Hi, guys

    I'm just getting to learn about microcontrollers recently.
    I ran into a couple problems choosing a controller.
    I'm asking for your help and suggestions from your knowledge and experience.

    Two cases,
    I need to read two analog sensors at 100Hz, average about 5 samples, output serial status message.

    I need to read in 8 sensors at 16 bit resolution at 1kHz, Measure state at 100Hz with a Kalman filter, control 3 actuators with a PWM, update state info over CAN.

    I had Luminary Micro LM3S8961 in mind for 2nd case, but what do you guys think?

    Thanks for your time,
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Have you looked at the PIC or the AVR?

    hgmjr
     
  3. sjkim0329

    Thread Starter Member

    Oct 19, 2008
    12
    0
    Yes, I did try to find something at PIC. Other than going through all the data sheet and try to find out which controller works the best, is there any other way to find one?
    Because there are a lot of controllers out there.
    Thanks.
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Don't know about the PIC but the AVR only has a 12-bit A-to-D converter. Is it possible for you to get away with 12 bits of resolution?

    hgmjr
     
  5. sjkim0329

    Thread Starter Member

    Oct 19, 2008
    12
    0
    I could try. So AVR can be done with 12 bit of revolution?
    if it has to be 16 bit. Do you think PIC would have it tho?
     
  6. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    I took a second look at the AVR device list and while there is an AVR with a 12-bit A-to-D, the device is not in a through-hole package. The through-hole device only has a 10-bit A-to-D.

    hgmjr
     
  7. sjkim0329

    Thread Starter Member

    Oct 19, 2008
    12
    0
    I wanted to make sure. I'm looking for 2 different controllers.
    Not both cases have to be working for one.
    I think you might have misunderstood it.
     
  8. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    I was thinking that the second case was the more stringent of the two cases. My thought was that the solution for the second case would be a shoe-in for the first case.

    hgmjr
     
  9. nanovate

    Distinguished Member

    May 7, 2007
    665
    1
    The Luminary Micro stuff is only 10-bits.

    PIC18 might be an option but it is only 10MIPS and you need to implement a Kalman filter
    PIC24 is another option -- 40MIPS and 12-bit 500kSPS 10-ch
    student compilers (certain optimzations reduced)

    AVR XMEGA
    dual 2MSPS 12-bit ADC (16-ch)
    32MIPS
    DMA
    unlimited free compiler

    Silabs
    25 MIPS C0805F064 has dual 1MSPS 16-bit ADC
    DMA
    limited free compiler
     
  10. AlexR

    Well-Known Member

    Jan 16, 2008
    735
    54
    Both AVR and PIC limit their DtoA to 10 or 12 bits (depending on the part). If you really need 16 bits you have to go to an external AtoD chip but that leads to the question do you really need 16 bit, that's 65 thousand voltage steps! Is you reference voltage stable enough to get meaningful results from a 16 bit conversion or is this a case of the more bits the better the specs look.
     
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