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ADS1248 SPI command problem

bart loeters
Prodigy 20 points
Other Parts Discussed in Thread: ADS1248

Hello,

I am trying to get the ADS1248 working. I've set up all the SPI communication pins, but the chip won't seem to "listen".

Instead it keeps converting at 5 SPS (I can see the DREADY pin latching at 200mS). When i send a SDATAC or WREG command, nothing happens.

What am i doing wrong?

This is a screenshot from an SDATAC command, now the ADC should stop converting but it doesn't.

  • 0
    TI__Guru* 98025 points

    Bart,


    The SDATAC command does not stop the ADC from converting, it simply stops the ADC from putting the output data on DOUT with every conversion. In comparison, without RDATAC, you need RDATA to tell the device to put the data onto the DOUT register each time you want to read the data.

    If you want the device to stop converting, you can either issue the SLEEP opcode, or pull the START pin low.


    Joseph Wu

  • 0
    TI__Guru* 98025 points

    Bart,



    Also, the waveforms you posted look correct. If you're having problems with WREG, let me know what you're clocking in and what the issue is.


    One thing you could try would be to issue the SLEEP command to make sure the /DRDY clocks stop after the conversion. Or you could change the data rate to see that the /DRDY clocks change their period.


    Regardless, let me know if that answers your question. If you have other questions, feel free to post back to the forum.

    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 20 points

    Hello Joseph,

    Thanks for the reply.

    After trying everything, i just realize that my RESET pin timing was not correct.

    After using an 20 mS delay timer when the RESET pin is pulled high, everything starts working like a charm ;)

    About the SDATAC command, it makes sense now. I will use the START pin for creating a "waiting state"

    Thanks,

    Bart