Converting from 5.19 (Hardware readback) Format
I am attempting to find the relation between the 5.19 values I receive and the strength of the signal that I input. When I put in a 1 V rms signal I get the values of 0x00, 0x79, 0xdf, 0x6b which when converted from hex to integer is 7987051, but when I put in a .5 V rms signal I get a value of 0x00, 0x72, 0x13, 0xF4, which when converted from hex to integer is 7476212. So the relation between those two values is 0.936 rather than 0.5. Is there some equation that relates these two values?
Any help is much appreciated. Thank you.
Hello,
Which SigmaDSP are you using, and how are you reading back the value? Are you using a peak envelope? Please post some more information and I will be glad to help.
Oh, and also, this thread contains lots of useful information on reading back signals:
https://ez.analog.com/message/7669
And this thread contains a description of the number formats in SigmaDSP:
I am using an ADAU1761. Below is a picture of the setup I am running in SigmaStudio, I am not running the simulation in the picture.
I am using a function generator to create the 1 V rms and 0.5 V rms signals. My goal is to place another board in between the generated signal and the inputs to my SigmaDSP and read the new signal strength.
Hello,
The cell you are using has a built-in filter that limits the measurement to a certain frequency band. This means that the readback level will vary depending on the frequency content of your input signal. You can change the filter by clicking on the small red "Wnd" button in the lower left corner of the cell.
To get a frequency-independent level measurement, please try using the running average cell (plus the DSP readback cell) as described in this thread: https://ez.analog.com/message/7669
In particular, check out the Envelope Implementations section of that thread.
Also note that the ADAU1761's readback format is 5.23, not 5.19, so you have some additional accuracy on the low end.
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