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Entry  Wed May 22 15:48:56 2013, Jamie, Update, SUS, Turn off zero padding in DAC outputs 
    Reply  Thu May 23 10:20:33 2013, Jamie, Update, SUS, Turn off zero padding in DAC outputs 
Message ID: 8625     Entry time: Thu May 23 10:20:33 2013     In reply to: 8617
Author: Jamie 
Type: Update 
Category: SUS 
Subject: Turn off zero padding in DAC outputs 


After the results of the analysis in the #8598 thread, I have added the "no_zero_pad=1" flag to the cdsParameters block of all SUS models:

  • c1mcs
  • c1sus
  • c1scx
  • c1scy

The upsampling to the 64 kHz DAC output will now be done with sample-holds, instead of zero-pads.  This should reduce the 32 kHz lines we were noticing in the analog DAC output.

I note, though, that Brian Lantz points out that this might actually introduce a delay of about a half sample.  We will continue to investigate.

In any event, I have rebuilt and installed all models listed above.  I will restart as soon as opportunity allows.

I have restarted all the suspension models with the new no_zero_pad flag for the DAC upsampling.  Everything came up fine and all optics are damped as expected (except for concerns about c1scy which I'll note in a followup).

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