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ADS1120: daisy chaining

andrea palamara
Prodigy 20 points
Part Number: ADS1120

Good morning everybody.

I'm about to use ADS1120 in a new design. Because of lack of Chip Select, I'd like to know if these devices are daisy chainable.

On the datasheet there no mention about it, but in the parametric search of the website, choosing "daisy-chainable" as a parameter, the ADS1120 is one of the proposed devices.

If the device is really usable in daisy chain mode, any suggestion / caution on the link among devices?

Thank you for helping.

Regards

Andrea Palamara

  • 0
    TI__Guru** 113765 points

    Hi Andrea,

    Welcome to the E2E forum!  Unfortunately the ADS1120 is not daisy chainable.  We will have to check into why this device shows up in the search.  Thanks for letting us know.  There are some ways to get around the CS issue.  How many devices do you need to use?  Can you share more about the application?

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    TI__Guru** 113765 points
    Hi Andrea,

    Just so that we are thinking the same, I took your original post to mean that you do not have a GPIO available to be used as a CS and wanted to know if the device is daisy chainable. Just so that we are clear, the ADS1120 does have a CS pin. It is possible to connect many ADS1120 on the same SPI bus using the CS pin. If you have GPIO available, then you should be able to use the ADS1120.

    Best regards,
    Bob B
  • 0 in reply to Bob Benjamin
    Prodigy 20 points

    Hello and thank you for your reply.

    Actually, I've been not so clear. My problem is that i need to use four ADS1120, controlled through an SPI. The SPI is a so called MibSPI from Texas microcontroller, so with additional features on data self managemet. Unfortunately because of internal pin muxing on microcontroller, only 3 out of 4 chip selet on the MibSPI are available in my project. Using a GPIO as CHIP SELECT for the device is obviously possible, but nullifies the advantages of using the MibSPI instead of a "simple" SPI.

    By the way,

    thank you for the support,

    regards

    Andrea

  • 0 in reply to andrea palamara
    TI__Guru** 113765 points
    Hi Andrea,

    Thanks for the updated information. I'm not a MibSPI expert, but my basic understanding is the frame can be 1 to 16 bits. The ADS1120 is a 16-bit device, with communication in byte increments. However the communication transaction requires that CS stay low throughout the entire transaction. Some commands are a single byte, while others can be as long 5 bytes. For this reason it is usually easiest to control CS using GPIO.

    Best regards,
    Bob B