[sdiy] ATSamD4 Breakout Board

nvawter nvawter at media.mit.edu
Mon Nov 9 23:06:43 CET 2015


On 2015-11-09 16:32, Eric Brombaugh wrote:
> It works fine but the 12-bit output might be limiting in some 
> situations.


IIRC this app note correctly:     
http://www.atmel.com/Images/doc8003.pdf

It shows how N bit sampling can be turned into N+M bit samples through 
oversampling at (4^M) times.  I think this would work well for DACs, 
too.

That (4^M) sounds very expensive to do, but there is a sweet spot in 
turning 12-bit into 14-bit by upsampling 16x.  14-bit = 12-bit * (2^2).  
That would mean a 44 kHz output routine would have to run a 705 kHz 
routine to upsample and synthesize a new sample every 16 times (@44kHz), 
but I believe the oversampling math is nearly the same as linear 
interpolation.  (you don't have to re-synth the whole synth loop at 705 
kHz, only do the interp).

Something to think about!  I'd love to try it sometime...   could be an 
easy experiment even with something like my Teensy 3.1....


Also on the topic STM and oversampling: I took a seminar on the STM32L4 
(low-power STM32F4) last month...  The newer parts have *built-in* 
oversampling on the ADC side!  I think it went up to 256x?  I haven't 
researched what other parts have this as well, but I wouldn't be 
surprise to see it propagate into others.  It also has a built-in 
convolution for up to 1024x sigma-delta samples!  amazing age we live 
in...



> http://ebrombaugh.studionebula.com/synth/f373_mod/index.html

oh my god, Eric, knocked it out of the park again.  we're getting closer 
and closer to Lego synth modules/max/msp in a Eurorack module all the 
time....




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