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ADS1196 problem

Jonathan Whitfield
Prodigy 70 points
Other Parts Discussed in Thread: ADS1196

I am interfacing an ADS1196 with an ATxmega256a3B and I am having an issue reading and writing to the registers.  There was an issue with the design of the PCB and the CLKSEL pin no the ADS was left unattached to the MCU.  An attempt to fix it was to tie it to DVDD with a small wire.  Could this be the root of the problem?  I know on page 64 of the datasheet it clearly states that all inputs must be tied low on start up which is why I'm worried that this pin is causing the problems.  I'm just trying to find out if this is the issue before I spend the afternoon on an oscilloscope trying to check the SPI lines.

 

thanks,

 

Jon

  • 0
    TI__Guru**** 171626 points

    Hi Jon,

    Sorry for the delay in getting back to you.  The CLKSEL pin of the ADS1196 being open should not have damaged the device, it should only cause possible erratic behavior and may be the root cause of you not being able to read/write to the registers.  Floating pins can sometimes drift high enough that the device acts like the pin is high and enables the internal oscillator - they can also go low and shut it off, so fixing the pin to the DVDD rail with a small wire is the right approach here. 

    There have been others posting here that have had trouble getting the SPI timing right, so you might want to review these logic analyser plots:

    http://e2e.ti.com/support/data_converters/precision_data_converters/m/videos__files/358662.aspx

    One additional thing that I'd like to mention is that the RESV1 pin needs to be tied to ground.  I've seen a few others miss that connection on their PC boards and that can cause problems with the SPI communication.

     

  • 0 in reply to Tom Hendrick
    Prodigy 70 points

    Thanks for the reply.  I finally got the initialization up and running.  The CLKSEL pin is permanently tied high and delays had to be added to get the timing right (shown below)  One issue that was unexpected with my design was using PORTB on the ATxmega.  Fair warning to anyone using an ATxmega, pins 4-7 on PORTB, these are also used by JTAG.  The JTAGEN fuse has to be disabled before these pins can be fully controlled and unfortunately for me PWDN, START and RESET were on PORTB pins 4-6.  After a lot of frustration its all worked out and works perfectly now.

    Thanks for the help

     

  • 0 in reply to Jonathan Whitfield
    TI__Guru**** 171626 points

    Hi Jon,

    Again, my apologies for the delay in getting back to you but I am happy to hear that the ADS1196 is now working in your setup!

    Let me know if you want more detail on one of our controllers - I'd be happy to try and talk you into using a Stellaris or MSP430 device on this or perhaps your next project.