Re: [oc] 1-bit DAC Project

["Carl van Schaik" <carl@openfuel.com>]

Hi All,

I over this weekend wrote an experimental 1-bit DAC
from some literature I had.
Wired it up with a FIFO and wrote a program for the
host PC to dump data across the PCI bus.

all I do is:
"mpg123 -s /dir/MusicFile.mp3 | dacoutput"
dacoutput is a program that monitors the
fifo size on the FPGA and sends data when
necessary.

All, I can is... WOW!
I was totally amazed at the quality you can yet, all from
about 10 lines of VHDL for the actual modulator.
I made a simple RC filter and sent the audio to my
speakers.

I'll post the code when I workout how (under
an "experimental" directory).... Need to make a new project?
Code should be usable by others.
It implements a wishbone interface (I use a bus converter,
I wrote a MemAD bus --> wishbone bus master)

No docs as yet. I'm busy this week with Thesis work
but I'll try get to them.

regards
Carl

----- Original Message ----- 
From: "Ravi Nimmagadda" <gnd_zro@yahoo.com>
To: "Carl van Schaik" <carl@openfuel.com>
Sent: Monday, August 27, 2001 8:15 AM
Subject: Re: [oc] 1-bit DAC Project


> Hi Carl,
> Thanks a lot for your reply. Please do let me know
> once you have additional information(specifications,
> plan of actions etc).
> Regards
> Ravi
> 
> --- Carl van Schaik <carl@openfuel.com> wrote:
> > Ravi,
> > 
> > I think there is a possibility for a reasonable
> > sized project.
> > I'll start by first writing a VERY simple test
> > version
> > to play with the sigma-delta modulation (encoding),
> > but the
> > design should ultimately contain a wishbone
> > interface with DMA capabilities, sample/bit rate
> > conversions, stereo, mono, volume, ?3D?... etc
> > 
> > also, is an A/D converter possible, for sound
> > input???
> > (may need more external hardware)
> > 
> > I'll test the code on my PCI card, make a simple
> > sound card  /dev/dsp type device for the host PC.
> > 
> > help would be gladly appreciated.
> > The various encoders can be developed
> > along the way, allowing people to choose the
> > encoder with complexity, speed and resource
> > requirements
> > for their budget.
> > A lot of theoretical work can go into the
> > sigma-delta encoders to optimise the efficiency,
> > qualtily (SNR), resource requirements etc.
> > 
> > Hopefully we can discuss the project in more
> > depth soon, get some specifications together
> > and some plans for action.
> > 
> > regards
> > Carl
> > 
> > > Hi Carl,
> > > What would be the size of the DAC project? If it
> > > involves multiple designers I would like to work
> > on
> > > the project. I have been working as an ASIC
> > designer
> > > for the past three and half years primarly on
> > chips
> > > for networking systems/devices. Please let me know
> > > your thoughts.
> > > Regards
> > > Ravi
> > > --- Carl van Schaik <carl@openfuel.com> wrote:
> > > > Hi
> > > > 
> > > > Talking about new projects, I am keen on
> > > > implementing
> > > > a 1-bit DAC, that is produce sound output
> > directly
> > > > from an FPGA. It's an interresting project
> > because
> > > > of the scope for optimisations and algorthyms. A
> > > > good
> > > > 1-bit DAC is quite difficult to design.
> > > > 
> > > > regards
> > > > Carl van Schaik
> > > > --
> > > > OpenFuel Pty Ltd.
> > > > 
> > > 
> > > 
> > > __________________________________________________
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> 
> 
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