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ADS130E08: SPI-EDMA Interface - ADS130E08

Bhaskar Reddy
Intellectual 980 points
Part Number: ADS130E08


We are planning to interface ADS130E08 to a DSP with SPI and use EMDA to pull in the data at every 250usec. We'll be connecting multiple ADCs (around 10 ) to one SPI in daisy chain mode.

The concern here is with the bit pattern.

As per the data sheet, in continuous conversion mode for every DRDY, each ADC sends 152 bits + 1 extra bit.

"Status and Data from the first ADS130E08 appear first on DOUT, followed by a don’t care bit, and finally by the status and data words from the second ADS130E08 device"

This extra bit is a concern while using EDMA.

Any suggestions other than reshuffling the bits, on how to handle this extra bit while using daisy chain mode with SPI and EDMA. 

  • 0
    TI__Guru 66816 points

    Hello Bhaskar,

    Thanks for your post.

    Unfortunately, this is a known bug in the digital and there is just isn't an easy workaround. Whether you are using EDMA or not, I believe the only way to handle this is to account for 153 total bits per device times 'n' devices, then parse the data later to separate the status words, channel data, and "don't care" bits.

    Please let us know if you have any further questions.

    Best Regards,

  • 0 in reply to Ryan Andrews
    Intellectual 980 points

    Thank you Ryan,

    Can you please suggest efficient way to parse these 153xN bits. 

    From 20th byte on words, every byte need to be processed to re-arrange the bits. Thats lot of software overhead.

    DSP gets such data from 12 ADCs every 125usec.

  • 0 in reply to Bhaskar Reddy
    TI__Guru 66816 points
    Hi Bhaskar,

    I understand that this bug creates a lot of overhead for our customers who wish to use this device in a daisy-chain configuration. For that I apologize, there just isn't a simple way to work around it.

    The only other option I can think of is to use independent /CS signals from your DSP and allow the ADCs to share the same SPI bus. However, I understand that you will not be able to use the EDMA in this case.

    Best Regards,
  • 0 in reply to Ryan Andrews
    Intellectual 980 points
    Thank you Ryan for the quick answers.
    We are planning to use CS signals from DSP.
    I hope we can still use EDMA by sending out CS signals on "Transmit event linked EDMA" using SPIDAT1. Correct me if I'm wrong.
    DSPs like c6746 have 8 CS pins on SPI1 and 6 CS pins on SPI0.
  • 0 in reply to Bhaskar Reddy
    TI__Guru 66816 points

    Hi Bhaskar,

    If you have multiple /CS pins available, then perhaps that is the simplest solution for you. I'm not familiar with our DSPs, but I was under the assumption that EDMA would not allow you to use multiple /CS - if I'm wrong, then you are good to go!

    Best Regards,