Sigma 300 (ADAU145x) Slew Volume Rates

     Slew volume controls can filter noisy control inputs and minimize clicks.  Often the desired slew rate can be found by experiment.  However, in some applications it would help to know the actual slew rate a given setting yields.  For example, the ADAU1701's slew rates are described at https://ez.analog.com/message/156092#156092

    The -1452's slew volume controls are different (and more versatile) than those of older SogmaDSPs,  There's separate rise and fall settings, each with several curves to choose from.  The "RC" curve setting shown here provides slewing similar to that of the older slew volume blocks, thus the slew rates can be measured the same way (see the post cited above).  Although this RC curve is exponential in nature (it follows the RC characteristic that includes the term e^(-t/RC), the -1452 slew block also offers a separate exponential choice. Testing the -1452's RC slewing this way results in the table below.  Slew times are given as a time constant as well as the dB/s rate often specified for SigmaDSP dynamics processors.

The Sigma 300's Exponential slewing operates in ways both similar to, and different from, the RC slewing.  The post at Sigma 300 (ADAU145x) Exponential Slewing describes the differences.



    Linear slew settings yield these 10 -- 90 % rise and fall times.  If you prefer 0 -- 100 % times, multiply these times by 1.25..

Parents
    •  Super User 
    on Feb 25, 2016 8:52 AM

         Hello,

         Yes, I checked the Wiki and found not even the GUI slew rate info I had worked out, let alone anything about uC control of this very useful block.  So it looks like we'll have to figure this out on our own.  You're on the right track with your trying different settings while noting the resulting four-byte parameter register value.  Rather than viewing the PARAMS.dat file after each change, you can get immediate feedback from the Capture Window:

         With the default linear slew modes as shown, setting "1" in first the rise and then the fall boxes caused the parameter words shown in the Capture Window.  Based on this and a few additional trials, I concluded that the linear slew settings appear like this:

         In accord with the extent of the runtime adjustments your system requires, you can work this method to deduce what register values correspond to the GUI settings.  Sorry that you need to reverse engineer these parameters!

         Best regards,

         Bob

Reply
    •  Super User 
    on Feb 25, 2016 8:52 AM

         Hello,

         Yes, I checked the Wiki and found not even the GUI slew rate info I had worked out, let alone anything about uC control of this very useful block.  So it looks like we'll have to figure this out on our own.  You're on the right track with your trying different settings while noting the resulting four-byte parameter register value.  Rather than viewing the PARAMS.dat file after each change, you can get immediate feedback from the Capture Window:

         With the default linear slew modes as shown, setting "1" in first the rise and then the fall boxes caused the parameter words shown in the Capture Window.  Based on this and a few additional trials, I concluded that the linear slew settings appear like this:

         In accord with the extent of the runtime adjustments your system requires, you can work this method to deduce what register values correspond to the GUI settings.  Sorry that you need to reverse engineer these parameters!

         Best regards,

         Bob

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