[sdiy] FracRak digital module?

[Paul Burns]

And then there is this ... the potential successor to FPGAs
http://www.technologyreview.com/computing/37406/?p1=A1&a=f

regards

Paul

-----Original Message-----
From: synth-diy-bounces at dropmix.xs4all.nl
[mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Scott Gravenhorst
Sent: 22 April 2011 15:57
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] FracRak digital module?

David Betz <dbetz at xlisper.com> wrote:
>I'm thinking of building a FracRak format modular synthesizer and would 
>like to find a module in that format that has some analog inputs and 
>outputs and a microcontroller or DSP with open source firmware that can 
>be loaded with custom code. Actually, something with an FPGA would be 
>even nicer. Does anyone know of something like that that would fit into 
>a modular system? A few years ago there was a module called PSIM-1 that 
>had a PIC chip but it is no longer being made.

If you're interested in PIC processors, I'd look at the Microchip dsPIC
device which is 16 bit and can have nice audio capable devices right inside
the chip such as ADC, DAC and UARTs.  These have some true DSP capacity with
a degree of parallelism allowing for such things as single cycle per tap FIR
filters.  They are even available in DIP.  I understand there is a useful
free C compiler available as well.  Not sure about "open source firmware",
but I would think/hope there is public domain code out there that could be
used directly or modified to your special purposes.  (Please note that I'm
an assembly language guy)

Since you mentioned FPGA (as even nicer) I would consider using an FPGA
development board behind the panel.  They can be very economical because
they are subsidized by the FPGA mfr.  These boards can have some nice
peripherals already available (such as DRAM, DAC, ADC).  As you may know
from my previous postings, I use FPGA development boards to implement
monophonic and polyphonic synthesizers.  It's been a while since I've looked
at that market, but when I bought mine, the bang-for-buck factor was quite
high (IMO).  I use Xilinx, but I'd bet there are similar offerings for
Altera.  As for "open source", not sure what you would mean in an FPGA
world, but at least for Xilinx, the "compiler" can be free (or paid for to
get somewhat more advanced features).  In fact, the software I've used to
generate my designs is all $0.00 stuff and does the job quite well.  The
boards I have all incorporate a Flash bit-file loader that can be user
programmed to allow the device to assume functionality when powered on.  The
downside of the boards I have is that the FGPAs are all BGA package and not
easily soldered by human hands, but they have the advantage of being
potentially internally large.

Alternatively, if you are interested in making your own PCB, there are some
FPGAs available in TQFP that are still large enough to make a reasonably
powerful polysynth (16 voices...).

-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
-- FPGA MIDI Synthesizer Information: home1.gte.net/res0658s/FPGA_synth/
-- FatMan: home1.gte.net/res0658s/fatman/
-- NonFatMan: home1.gte.net/res0658s/electronics/
-- When the going gets tough, the tough use the command line.

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