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ADS8681: Incorrect Adc count

Ginc Geo
Prodigy 10 points
Part Number: ADS8681

I am trying to interface ads8681 with pic24f. I am using 3*vref input range and for that i had configured the register RANGE_SEL register. I am getting incorrect adc values.I configured my spi module with CKE = 1 and CKP=0 and Iam sending NOP signals for providing clock signals from the master for the slave to send adc count values. I have checked the

RVS line which is toggling while running my code

 the reset pin is pull uped by a resistor to 5v

AVdd = 5V

DVdd = 3.3v

Can someone help me with this??

  • 0
    TI__Mastermind 45595 points

    Hello Ginc,

    I list a couple of things which need your check and your confirmation, thanks.

    1.  How about your CONVST/CS signal? this pin should be controlled by your MCU, a rising edge will bring ADC from acquisition phase to conversion phase and initiate the conversion, when /CS is low, ADC takes control of the data bus and MCU can retrieve the conversion data.

    2.  Are you sending any command to get the data?

    3. Have you configured SDI_MODE[1:0] in SDI_CTL_REG resister?

    4. What's your analog input signal you are testing and what's  the output code your are getting?

    Please upload your schematic to check, thanks.

    Best regards

    Dale