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How to use SPI only with ADS1247

Simon Westphahl
Prodigy 40 points
Other Parts Discussed in Thread: ADS1247, ADS1220

Hi all,

I'm currently evaluating the ADS1247 and I want to test the SPI interface without dealing with the ADC part for now. I'm using a BeagleBone Black (BBB) as the SPI master. Is it enough to connect the ADS1247 like follows?

  • DVDD -> +3.3V
  • DGND -> GND
  • SCLK -> 1MHz @ BBB
  • DIN -> MOSI @ BBB
  • DOUT -> MISO @ BBB
  • CS -> CS @ BBB

Do I also have to pull RESET to GND? What about the START pin?

Thanks for your help!

Best regards,
Simon

  • 0
    TI__Guru** 113765 points

    Hi Simon,

    Welcome to the forum!  RESET must be high or the device will be held in reset.  START must also be high to read and write register values.  The CLK must be tied low for use of the internal oscillator, or you must provide a clock.  I would also suggest that you connect AVDD and AVSS to the +3.3V and GND at this time as well.

    One other consideration and that is CS must be low throughout the entire communication transaction (not just each byte portion of a multi-byte communication transaction).

    You might also take a look at the ADS1220, which is very similar to the function of the ADS1247 but has simpler operation.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 40 points

    Hi Bob,

    thanks for your suggestion. I now connected the ADS1247 like follows:

    1. DVDD -> +3.3V
    2. DGND -> GND
    3. CLK -> GND
    4. RESET -> +3.3V
    5. (unused)
    6. (unused)
    7. (unused)
    8. (unused
    9. (unused)
    10. (unused)
    11. (unused)
    12. (unused)
    13. AVSS -> GND
    14. AVDD -> +3.3V
    15. START -> +3.3V
    16. CS -> CS@BBB
    17. (unused)
    18. DOUT -> MISO@BBB
    19. DIN -> MOSI@BBB
    20. SCLK -> CLK@BBB @ 1MHz

    It now works perfectly fine. I think the problem was that I did not connect the START pin. I will also have a look at the ADS1220.

    Thanks for your help!

    Best regards,
    SImon