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ADS131A04: Initialization Assumptions and Questions

Todd Anderson3
Intellectual 370 points
Part Number: ADS131A04

All:

I will be working with the ADS131A04, and I have some questions.

Based on the datasheet and the example code, here is what I have seen for recommended initialization:

1. Set RESET pin high.

2. Wait for nDRDY to go low, or wait ~5 msec.

3. Send NULL.

4. Receive READY.

5. Send UNLOCK.

6. Receive UNLOCKED.

7. Send D_SYS_CFG contents.

8. Verify contents of D_SYS_CFG.

9. Send CLK1

10. Verify contents of CLK1

11. Send CLK2

12. Verify contents of CLK2

13. Send ADC_ENA

14. Send WAKEUP.

15. Receive 4 values first for output buffers to fill.

Questions:

1. Does the part assume 8bit SPI mode? (with Null output between received bytes?)

2. If the A_SYS_CFG needs to be configured, is that done before D_SYS_CFG?

3. If multiple ADCs are being used, does each ADC value need to be read 4 times after initialization?

Probably more questions to come...

Regards,

Todd Anderson

  • 0
    TI__Guru 63995 points

    Hi Todd,

    Thanks for the interest in the ADS131A04.  A number of our lead team members are out for the US holidays including our main support members for this product.

    Please expect some delays in the replies until the engineers return.  Until then, here are a few comments:

    1.)  Most processors we work with still have 8-bit shift registers in the SPI engines and this will work along with other frame lengths that build to the full frame length.

    2.)  Not 100% sure, but I don't believe so.  Recommend adding the write/read to this register between steps 12 and 13 so the digital is configured fully and then the analog gets configured and then enabled afterwards with the "ADC_ENA" command.

    3.)  I believe so as the requirements are for the internal shift buffers to fill with data which would only happen when converting. 

  • 0 in reply to Collin Wells
    Intellectual 370 points

    More questions:

    Can I expect Status at the same frame as Command out, or is Status offset until first zero goes out?

    Do you get 24 bit data only in 24-bit and 32-bit word sizes?  If 16-bit word size, result is 16 bits?

    Regards,

    Todd Anderson

  • 0 in reply to Todd Anderson3
    TI__Guru 66516 points

    Hello Todd,

    The Status and Command words will be aligned to the beginning of the data frame and are always present whether in Standby Mode or without ADCs enabled (Figures 53 and 54). When the previous frame includes an SPI command input, the Status word in the next frame will contain the response to that command.

    Yes, 24-bit data is only available for word sizes of 24 bits or 32 bits. The 16-bit word size truncates the data to include only the most-significant 16 bits.

    Best regards,