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QSPI AD779x

Question asked by brian_in_nl on Apr 14, 2015
Latest reply on Apr 20, 2015 by jcolao

Hello,

 

I am hoping to daisy chain my ad779x devices.  (ad7794 right now but planning on ad7791).  The datasheets say they are qspi(tm) compatible.  What exactly does this mean?  I can find only limited information on this.  I have a hunch that it is not true because the wording seems to suggest that there are separate input and output registers in these devices?

 

I am presently working off the assumption that the /CS acts as a frame synchronization for a set of written bytes.

 

        cs=0;

        for(i=0;i<2;i++){

        spi.write(0x08);//mode register

        spi.write(0x20);//single conv.

        spi.write(rate);      

        }    

        cs=1;

 

In this case the same command is written to two devices and the /CS is used to frame them similar to what is discussed in AN-1248 pg. 6-7.  When I go to read the conversion out I've been writing two read commands and clocking out 6 bytes but I am not getting anything out.

 

        cs=0;

        spi.write(0x58);//read data reg 

        spi.write(0x58);//read data reg  

        for(i=0;i<3;i++){

        datain[i] = spi.write(0x00);

        }    

        for(i=3;i<6;i++){

        datain[i] = spi.write(0x00);

        }       

        cs=1;

 

Any help here would be appreciated. 

 

Brian

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