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what is wrong with my program? AD7780 simple issue

Question asked by Mayer on Sep 25, 2011
Latest reply on Oct 10, 2011 by RobK

Hi all
i wish to consult you in some problems regarding the part number (AD7780)
  i am seeking your assistance please

this is a high precision 24-bit ADC.

its a 2-wire interface which makes it simple and easy to use

 

it just requires sufficient number off clock cycles and it gets out a 32 bit word.

 

i read these 32 bit word and one of them which is the most important one was the RDY bit as i checked this bit's status and waited for it to come low the outputs reading i get are completely errors as follows.

 

i made a c program that reads the 24 bits of the conversions and the 8 bits of the status check by makeing simple 32 successive  (0 1) clock.

and i am expecting the output of the 8 status bits to be 00001101 to identify my current preferences that i am useing and to identify if the conversions where performed correctly or not.

anyways

any other result but this 00001101 represents that i am doing a wrong conversion like for example the error bit which is the third bit from the Msb gives me 1 instead of 0 .

 

 

 

 

the very strange thing that happend that when i took my feedback and waited for the ready bit to go low which is the Msb (first bit of the 8 status bits) it gave me wrong output and the result was nothing almost.

 

 

and when i took the feedback(waited for this bit to go low) on the last bit the (lsb of the 8 status bits) which is just a normal bit to identify if the conversion has went with no errors or not the out put was correct and the 8 status bits was 00001101 but there was a very annoying problem that the output noise was very high almost 500/16777216 (500/(2^24))

so please someone answer me with this strange issue

thankyou.

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