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ADS7851: SPI Data Acquisition with Beaglebone Black

Part Number: ADS7851

Hello team,

I'm working on a design that utilizes the ADS7851 and Beaglebone Black for data acquisition. I'm a bit unfamiliar with SPI communication so I am a little confused on how to wire up these devices.

The ADS7851 has two SDO SPI outputs: SDO-B, SDO-A

and two SPI inputs: SCLK and CS 

The Beaglebone Black has two SPI intefaces on the expansion header:

####SPI0 :

  • CS0 : P9_17
  • MISO : P9_21
  • MOSI : P9_18
  • SCLK : P9_22

####SPI1 :

  • CS0 : P9_28
  • CS1 : P9_42
  • MISO : P9_29
  • MOSI : P9_30
  • SCLK : P9_31

Would it be okay to make these connections from the ADC7851 to the Beaglebone Black expansion header?:

SDO-A to P9_21  

SDO-B to P9_29

SCLK to P9_31

CS to P9_28

Regards,

I.K. 

  • Hi I.K.,

    Your SPI connections are correct, but you will need to connect the SCLK output from SPI1 to the SCLK of SPI0 and set SPI0 as a slave. I recommend reaching out to the BB Black team for details on how to do that.

    Let me know if you have any further questions about SPI for this device.
  • In reply to Evan Sawyer:

    Thanks, Evan. I'll crosspost this to the BB Black team as well.

    Regards,
    I.K.
  • In reply to Evan Sawyer:

    Hi Evan,

    It turns out I can't configure the SPI interface on the BB Black as a slave.

    If I use two of the ADS7054 instead (www.ti.com/.../ads7054.pdf) do you think it'd be better to configure it like the below picture, where I have the BB Black SPI interfaces acting as master and the two ADS7054 as slaves?

    In this case, it looks like I'd need to have SPI0 and SPI1 provide separate 24MHz clocks for the ADC SCLK inputs. Is this a plausible solution?

    Regards,

    I.K.

  • In reply to I.K. Anyiam:

    Hi I.K.,

    Yes, you can most certainly use 2x ADS7054 to simultaneously sample two signals. We have a design that interleaves multiple ADS7056 devices (a faster, single-ended version of the ADS7054) to achieve a higher throughput. While not identical to what you are doing, the channel to channel sampling is just as critical in an interleaved application as a simultaneous sampling one.

    If interested, here is a link to that design. It may help you with your system.

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