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ADAU17xx Data Readback format

Question asked by kautt on Oct 10, 2014
Latest reply on Oct 16, 2014 by mmmike

Hello All,

I have an ADAU17xx part talking to a microcontroller in my application. I'm trying to use the readback tool to read out some rms values from the codec over the I2C bus. I read that the format of this data is 5.23 here Numeric Formats [Analog Devices Wiki]


Lets take an example:-


From within Sigmastudio, I notice that the value 0x0F, 0x81, 0xB1, 0xC2 gets converted to -0.98676....


I cannot understand how that would be.


0x0F and 0x81 would mean that the 5 bit integer part is 11111 thereby making it -1 in decimal (negative twos complement) :-


   0        F        8       1

0000 (1111 1)000 0001


Yet the converted value in Sigmastudio is -0.98676....


What am I missing ?


Thanks for your time.