SynthModules

Dave,

The file is located in Files/miscellaneous/gc-sah-sr-qua.bas


http://launch.groups.yahoo.com/group/SynthModules/files/PSIM-1%20Programs/Miscellaneous/


gary



--- In SynthModules@yahoogroups.com, "djbrow54" <davebr@...> wrote:
>
> I'd be happy to look at it.  It's not an error with the PSIM but 
> rather different scales for input and output.
> 
> For input, the range is 1024 steps over 10 volts, or 9.76 mV 
> increments.
> 
> For output, the range is 4096 steps over 10.666 volts, or 2.60 mV 
> increments.
> 
> Thus to pass an input to output, the scale factor is (10/1024)X
> (4096/10.666) which is 3.75.
> 
> Thus to scale the input to output, it needs to be multiplied by 
> 3.75, (not 4).  I typically multiply by 15/4 to keep the math 
> integer based.
> 
> Note that 10.666 volts was chosen  to calibrate to semitone voltages 
> which are increments of 83.33 mV, or 32 increments.  Thus to 
> quantize to semitones, you simply zero the right 5 bits of the 
> output value.
> 
> I have a FAQ on my page which details a number of things I've 
> learned both with the PSIM and the AtomPro24 and 28.  It's right 
> below the header for my DJB PSIM Programs on
> http://www.modularsynthesis.com/modules/synthmodules/synthmodules.htm
> 
> In my quantizing (only) program, I did both the conversion and the 
> quantizing in the actual DAC output code.  Zeroing the right 5 bits 
> is the same as dividing by 32 and then multiplying by 32. 
> Multiplying by 3.75 and dividing by 32 is the same as multiplying by 
> 2 and dividing by 17 (ok, reasonably close).  The code I used to 
> scale, quantize, and output J1 to the DAC is:
> shiftout ser_data,clock,4,[((((in_j1*2)/17)*32)+49152)\16]
> 
> This keeps the code reasonably fast although I could have also 
> multiplied by 15/4 and zero'd the last 5 bits with code like:
> shiftout ser_data,clock,4,[((((in_j1*15)/4)&$0FE0)+49152)\16]
> 
> I couldn't find the program you were referring to.  Where is it?
> 
> Dave
> 
> --- In SynthModules@yahoogroups.com, "Gary Chang" <gchang@> wrote:
> >
> > Dave,
> > 
> > What seems like an eternity ago I mentioned that in a typical PSIM
> > application such as gc-sah-sr-qua.bas, there was an discrepency
> > between the input and the quantized voltage outputs when sending an
> > already quantized voltage through the PSIM.  You had commented on 
> the
> > fact that there was an error on the perceived voltage range of the
> > PSIM input, which is why the quantization error occurs.
> > 
> > Does this conversation sound memerable to you, Dave?  With Woody's
> > permission, I would love to have you look at this program to see if
> > you can correct this issue - otherwise, gc-sah-sr-qua.bas (stands 
> for
> > sample and hold - shift register - quantizer) is a really rockin
> > version of a Serge Sual Analog Shift Register...!
> > 
> > Gary
> >
>