Bob:

See my other message referring to the Motorola analog parts.

I don't have the software readily available. (It was a long time ago on
an Apple ][). The basic idea is that you A/D convert the audio then
compare it in software to the output of a counter used to approximate
the "leaky" integrator. The integrator is driven from the 3 or 4 bit
shift register implemented as shown in the block diagram for the
MC3418/MC34115.

I did a direct translation of the hardware to software without any
clever tricks needed. This shouldn't be hard to implement with a
PIC12C671 and an external DAC. Since the data rate is low, the DAC can
probably be a PWM type. One of the neat things about CVSD is that it is
very highly oversampled by its very nature. This makes anti-aliasing
filters easier.

If this isn't enough help, I can try to find the old 6502 software.


-- Rich


Bob Ammerman wrote:
>
> Hey, I've got the same problem. A system that contains a CVSD chip that has
> been obsoleted.
> I'm wondering if it is possible to do CVSD in firmware on a PIC.
>
> Does anybody know of a software implementation of CVSD on any platform
> whatsoever for which I can obtain the source code?
>
> Or a detailed description of the algorithm?
>
> Bob Ammerman
> RAm Systems
> (contract development of high performance, high function, low-level
> software)
>
> ----- Original Message -----
> From: Jinx <joecolquitt@CLEAR.NET.NZ>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Saturday, November 11, 2000 7:47 PM
> Subject: [EE]:Syllabic Integrator
>
> > Can someone please explain estimate and syllabic integrators. I've
> > looked around and keep coming up with the same three very similar
> > web pages eg
> >
> > http://www.users.zetnet.co.uk/ross/radio/iaru-4.htm
> >
> > I'd like to replace a DSP chip that performs CVSD  (Continuously
> > Variable Slope Delta) functions for converting waves to SRAM data.
> > The block diagram of the chip's input section shows the 10-bit ADC,
> > comparator, estimate integrator, and syllabic integrator. The output
> > is an adder + 10-bit DAC
> >
> > The chip produces a stream of 1-bit differences between samples
> > on audio range frequencies at 64k samples/sec. Is it possible to do
> > this in s/w (with external ADC/DAC) ? I like what the chip does and
> > would want to keep the same specs
> >
> > --
> > http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> > use mailto:listserv@mitvma.mit.edu?body=SET%20PICList%20DIGEST
> >
> >
> >
> >
>
> --
> http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> use mailto:listserv@mitvma.mit.edu?body=SET%20PICList%20DIGEST

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu