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Interfacing AD7730 to PIC 16F877

Question asked by swasthika.manaram on Mar 24, 2012
Latest reply on Oct 30, 2012 by TejaN

Dear All,

 

I'm doing a project of interfacing AD7730 with PIC16F877.

 

I am successfully communicating with internal registers of AD7730, but the problem is when I am going to read the data register it is showing only 0.

 

And RDY pin is not going to low, that to indicate new data is available.

 

Then I put some break points in codes and found that when I give the command to internal calibration, it is not performing.

 

Because if it is performing it should reset the Mode registry first three bits to 000, in my case all the time it is showing my last command only.

 

I used 5V for excitation and power-up the IC

ref+ and ref- are supplied same as VDD and VGND, and after voltage regulator 7805 , it is supplying 4.96V to those pins.

crystal oscillator for AD7730 is 4.952MHz ,and 15pF capacitors are fixed.

my load cell is 10mV full range with 5V excitation.

 

Procedure I used is

Write to the filter register first.

Then write to the Mode register for calibration.

 

Pls help me

 

  adc_write_byte(3);//Filter

   adc_write_byte(16);//00010000

    adc_write_byte(3);//00000011

     adc_write_byte(0);//00000000

 

         adc_write_byte(2);//Mode Internal full scale calibration

         adc_write_byte(176);//10110000

         adc_write_byte(128);//10000000

 

This adc_write_byte function was developed by myself and by writing and after reading same registry I found that communication is perfectly working.

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