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How are the signed floating point values read from the ADC stored in 14 bits?

Posted: Sun Aug 16, 2020 7:41 am
by Schrodinger1933
Hello all.

I am writing a custom app and would like to do processing on the signals from the ADC as well as configure the signals the DAC generates. I understand that the ADC and DAC have 14 bit resolution, but I do not understand how to work with this data. The IEEE standards I have seen for representing signed floating point values in binary have a standardized format for 32 and 64 bit data, but I am unsure how to apply that to 14 bit data. Any help is appreciated

Re: How are the signed floating point values read from the ADC stored in 14 bits?

Posted: Tue Aug 18, 2020 6:53 pm
by alex123go
Hello,

In page 25 of the ADC's datasheet (https://www.analog.com/media/en/technic ... 4314fa.pdf), you can see a table of the voltage to binary representation.

The ADC chip is setup for offset binary: 14'b0 = -1V, 14'b1 = +1V

The process is similar for the DACs (https://www.idt.com/us/en/document/dst/ ... -datasheet). Its nominal output is in current, but the "Amplifier & filter" block makes the conversion in Volts. For the DACs, I'm not sure if 14'b0 = 1V or -1V.

How to work with these data depends on what you want to do. If everything is done in the PL part (FPGA) you can always keep 14 bits and define your signals as signed(14-1 downto 0). If you want to interface with the processor, you might want to extend your data to 16 bits by adding 0s to work with integer.

Hope this helps.

Alex

Re: How are the signed floating point values read from the ADC stored in 14 bits?

Posted: Thu Aug 20, 2020 3:02 am
by Schrodinger1933
Thank you so much! I have been looking for that information for a while, that helps a lot :)

Re: How are the signed floating point values read from the ADC stored in 14 bits?

Posted: Thu Aug 20, 2020 8:47 pm
by alex123go
You're welcome! :)