Searching SBC/DSP board/microcontroller; 4ADC/1kHz/USB Host

Discussion in 'Embedded Systems and Microcontrollers' started by Yoreki, May 7, 2009.

  1. Yoreki

    Thread Starter New Member

    May 7, 2009
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    Hello,

    I am looking for something along the lines of a Single Board Computer (SBC), a Digital Signal Processing (DSP) board, or a microcontroller. Though I am open to any other suggestions, but what I essentially need to be able to do is the following.

    Requirements:
    - 4 channel ADC
    - Sample rate of 1kHz; meaning I want to be able to sample from all 4 channels at a rate of 1kHz, whether that means sampling each input individually (in a round-like fashion at a higher rate in order to complete sampling all 4 channels at an overall rate of 1kHz), or sampling all 4 channels at the same time each at a rate of 1kHz.
    - Can write to USB (USB Host port)​
    Project Breakdown: I have 4 analogue signals I need converted to digital signals, and stored on a USB key, at a rate of 1kHz.

    I am very new to working with these pieces of equipment, so please be understanding if I make any errors in talking about them, or am completely mistaken about the components to use.

    I have so far been steered in the direction of using a SBC or a DSP board. However, I’ve been searching for days going over board after board, and I can’t find anything that has a high enough sample rate. The closest I’ve found to what I need is a series of ARM single board computers, the TS-7000 series.

    http://www.embeddedarm.com/products/arm-sbc.php#ts-7800-series

    Other than the TS-7800, the others didn’t seem to come close enough. Even the TS-7800, after reading the manual closely and inquiring about the meanings of some parts, I still found that when operating with 4 channels the overall sample rate would only be 0.5kHz (2kHz/ch).

    I would really appreciate any advice, or experience that anyone can share with me. If you know of an actual component that fits my requirements that would be amazing, but even if you’re just able to steer me in a good direction it would be greatly appreciated.

    Thanks a lot, hope I can get some feedback soon,

    Tyler
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. Yoreki

    Thread Starter New Member

    May 7, 2009
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    First of all, thanks for the reply beenthere :)

    I took a look at the DI-710 and 720, and they both only seem to have the ability to connect/communicate to a computer through USB.

    What I'm looking for is the ability to write/record data (voltages) to a USB memory stick. Thus the need for a USB host port.

    I'm also looking to have to build something myself (I have an amplifier and bandpass filter already designed, and now I'm looking for the means to record the data) , while it's nice to be able to get this all in a ready made product I'm looking to make my own device for a specific task. That being said, my final device needs to be portable, and I think I would have trouble doing so if I was to use something the size of those data loggers.

    Any other ideas?

    Thanks again!
     
  4. nanovate

    Distinguished Member

    May 7, 2007
    665
    1
    What is the required resolution of the digitized signals?

    If all you need is to digitize the 4 signals then it might be easy -- the Atmel XMega or Silabs C8051F064 or external ADC + MCU . If you need to process them then you need to let us know what that processing is to determine if a DSP is really necessary.

    BTW the TS-7800's ADC is actually much faster than 2 kSPS but that is the speed they have programmed the AVR to sample at.
     
  5. Yoreki

    Thread Starter New Member

    May 7, 2009
    5
    0
    about 10-16 bits.

    I don't plan to do any processing before recording the data to the USB memory stick. All processing will be done on a PC afterward.

    *NOTE*: I had thought I'd already replied to this message earlier today, but apparently never posted it. I can't remember the devices clearly that you mentioned (I'm pretty sure I looked at the Atmel). I have to go for now, and I wont be back until Monday, but I wanted to make a post for now to let you know what I could quickly. Thanks for all your help, I'll post again Monday!*END NOTE*

    Does that mean I could program it to sample faster? Do you have any resources I could read up on to learn how to program the AVR to do that?
     
  6. John Luciani

    Active Member

    Apr 3, 2007
    477
    0
    You didn't mention the accuracy that you require for the conversion.

    The Atmel ATmega168 will do 15kSPS at 10bits resolution and 2LSB of accuracy.
    The device has either six or eight inputs depending on the package. Doing
    four channels at 1kSPS should not be a problem. If you need higher
    accuracy you would need an external A/D.

    To get to USB you would just use a serial to USB IC like the FTDI232RL.

    Take a look at the ADC section of the ATmega168 datasheet (pgs 243-258).

    (* jcl *)
     
  7. Yoreki

    Thread Starter New Member

    May 7, 2009
    5
    0
    Thanks for the suggestion John :)

    That does look like a good way to go. I actually was able to find a SBC with my desired specs: the APF27 dev_light board. Which I think will simplify some of the coding I'll need to do. So atm I'm leaning towards that.

    However, I am still curious, do you know what nanovate meant by

    I'd like to know more about how I can increase the sample rate by changing the code...

    Thanks again!
     
  8. nanovate

    Distinguished Member

    May 7, 2007
    665
    1
    The TS-7800 has an ATMega168 on the board which can do at least 15kSPS ( as Mr Luciani mentioned). Maybe the nice folks at Technologic can give you a version of the firmware for it with faster settings.
     
  9. Yoreki

    Thread Starter New Member

    May 7, 2009
    5
    0
    Oh, thanks. I hadn't realized the ATMega168 was what was on the TS-7800. Yea, I'll see what they say, otherwise I'll try to fiddle with the code myself.

    Thanks a lot you two.
     
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