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| Fred... |
 Posted: Sun Oct 25, 2009 4:46 pm |
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Guest
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I was wondering what DSP chip would be appropriate for a guitar pedal
effect. I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result. |
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| Fred... |
| Posted: Sun Oct 25, 2009 5:26 pm |
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On Oct 25, 11:08 pm, "mook johnson" <m... at (no spam) mook.net> wrote:
[quote]"Fred" <frederick.br... at (no spam) gmail.com> wrote in message
news:2c03acbb-9d7a-45b6-adc8-2e6924b1ff87 at (no spam) b18g2000vbl.googlegroups.com...
I was wondering what DSP chip would be appropriate for a guitar pedal
effect. I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result.
How simple is simple? A number of devices can do that. If you care about
audio quality I wouldn't use the build int ADCs and DACs though.
[/quote]
The function will be floating point and contain trig functions. Each
sample is run through the function once and outputed.
ADC and DAC convertion will need to either be contained in the chip or
sorted out separately.
I understand there are PICs out there and other similar things that
can do this, I'm just unfamiliar with there devices and trying to wade
though the websites to figure out what would work is kinda rough when
your clueless. :)
Fred |
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| miso at (no spam) sushi.com... |
| Posted: Sun Oct 25, 2009 6:17 pm |
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Guest
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On Oct 25, 9:04 pm, hal-use... at (no spam) ip-64-139-1-69.sjc.megapath.net (Hal
Murray) wrote:
[quote]In article <ae3a0936-286a-4a0f-9830-42a5ddf52... at (no spam) e18g2000vbe.googlegroups..com>,
Fred <frederick.br... at (no spam) gmail.com> writes:
On Oct 25, 11:08 pm, "mook johnson" <m... at (no spam) mook.net> wrote:
"Fred" <frederick.br... at (no spam) gmail.com> wrote in message
news:2c03acbb-9d7a-45b6-adc8-2e6924b1ff87 at (no spam) b18g2000vbl.googlegroups.com....
I was wondering what DSP chip would be appropriate for a guitar pedal
effect. I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result.
How simple is simple? A number of devices can do that. If you care about
audio quality I wouldn't use the build int ADCs and DACs though.
The function will be floating point and contain trig functions. Each
sample is run through the function once and outputed.
ADC and DAC convertion will need to either be contained in the chip or
sorted out separately.
I understand there are PICs out there and other similar things that
can do this, I'm just unfamiliar with there devices and trying to wade
though the websites to figure out what would work is kinda rough when
your clueless. :)
Are you going to build one or a million? If the latter, the cost of
the silicon is important. If you only build a few, the silicon is free..
The expense is the time to develop the software so you should look
for an software environment you like.
You said 96kHz. Call that 100 kHz, or 10 microseconds per sample.
You need a CPU that is fast enough to run your algorithim in the
alloted time. Trig functions can be messy. I'd suggest getting
a development board and timing things. (If you might buy a million,
the FEs will be helpful. If not...)
Why do you think you need floating point? The input isn't floating.
The output isn't floating.
As a (probably crazy) straw-man, you could consider table lookup.
It doesn't take much time, but it sure eats memory. It might be
worthwhile to implement the algorithim on a PC and look at it on
a graph. Can you compress that graph? Think interpolation,
or curve fitting. A cheap CPU with external memory might be less
expensive than a CPU fast enough to do the trig functions.
--
These are my opinions, not necessarily my employer's. I hate spam.
[/quote]
Coordic. |
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| Fred... |
| Posted: Sun Oct 25, 2009 8:48 pm |
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Guest
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On Oct 26, 12:17 am, "m... at (no spam) sushi.com" <m... at (no spam) sushi.com> wrote:
[quote]On Oct 25, 9:04 pm, hal-use... at (no spam) ip-64-139-1-69.sjc.megapath.net (Hal
Murray) wrote:
In article <ae3a0936-286a-4a0f-9830-42a5ddf52... at (no spam) e18g2000vbe.googlegroups.com>,
Fred <frederick.br... at (no spam) gmail.com> writes:
On Oct 25, 11:08 pm, "mook johnson" <m... at (no spam) mook.net> wrote:
"Fred" <frederick.br... at (no spam) gmail.com> wrote in message
news:2c03acbb-9d7a-45b6-adc8-2e6924b1ff87 at (no spam) b18g2000vbl.googlegroups.com...
I was wondering what DSP chip would be appropriate for a guitar pedal
effect. I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result.
How simple is simple? A number of devices can do that. If you care about
audio quality I wouldn't use the build int ADCs and DACs though.
The function will be floating point and contain trig functions. Each
sample is run through the function once and outputed.
ADC and DAC convertion will need to either be contained in the chip or
sorted out separately.
I understand there are PICs out there and other similar things that
can do this, I'm just unfamiliar with there devices and trying to wade
though the websites to figure out what would work is kinda rough when
your clueless. :)
Are you going to build one or a million? If the latter, the cost of
the silicon is important. If you only build a few, the silicon is free.
The expense is the time to develop the software so you should look
for an software environment you like.
You said 96kHz. Call that 100 kHz, or 10 microseconds per sample.
You need a CPU that is fast enough to run your algorithim in the
alloted time. Trig functions can be messy. I'd suggest getting
a development board and timing things. (If you might buy a million,
the FEs will be helpful. If not...)
Why do you think you need floating point? The input isn't floating.
The output isn't floating.
As a (probably crazy) straw-man, you could consider table lookup.
It doesn't take much time, but it sure eats memory. It might be
worthwhile to implement the algorithim on a PC and look at it on
a graph. Can you compress that graph? Think interpolation,
or curve fitting. A cheap CPU with external memory might be less
expensive than a CPU fast enough to do the trig functions.
--
These are my opinions, not necessarily my employer's. I hate spam.
Coordic.
[/quote]
I need to look at the different ways possible to do this, and hardware
to implement it.
Cordic looks interesting, I still need to figure out how to get the
ADC and DAC conversion done and the chip to run the function,
I also need to be able to have one user variable parameter a setting
knob that the the micro-controller would track in real time.along with
the input signal. |
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| mook johnson... |
| Posted: Sun Oct 25, 2009 9:08 pm |
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Guest
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"Fred" <frederick.brown at (no spam) gmail.com> wrote in message
news:2c03acbb-9d7a-45b6-adc8-2e6924b1ff87 at (no spam) b18g2000vbl.googlegroups.com...
[quote]I was wondering what DSP chip would be appropriate for a guitar pedal
effect. I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result.
[/quote]
How simple is simple? A number of devices can do that. If you care about
audio quality I wouldn't use the build int ADCs and DACs though. |
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| Hal Murray... |
| Posted: Sun Oct 25, 2009 10:04 pm |
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Guest
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In article <ae3a0936-286a-4a0f-9830-42a5ddf52564 at (no spam) e18g2000vbe.googlegroups.com>,
Fred <frederick.brown at (no spam) gmail.com> writes:
[quote]On Oct 25, 11:08 pm, "mook johnson" <m... at (no spam) mook.net> wrote:
"Fred" <frederick.br... at (no spam) gmail.com> wrote in message
news:2c03acbb-9d7a-45b6-adc8-2e6924b1ff87 at (no spam) b18g2000vbl.googlegroups.com...
I was wondering what DSP chip would be appropriate for a guitar pedal
effect. I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result.
How simple is simple? A number of devices can do that. If you care about
audio quality I wouldn't use the build int ADCs and DACs though.
The function will be floating point and contain trig functions. Each
sample is run through the function once and outputed.
ADC and DAC convertion will need to either be contained in the chip or
sorted out separately.
I understand there are PICs out there and other similar things that
can do this, I'm just unfamiliar with there devices and trying to wade
though the websites to figure out what would work is kinda rough when
your clueless. 
[/quote]
Are you going to build one or a million? If the latter, the cost of
the silicon is important. If you only build a few, the silicon is free.
The expense is the time to develop the software so you should look
for an software environment you like.
You said 96kHz. Call that 100 kHz, or 10 microseconds per sample.
You need a CPU that is fast enough to run your algorithim in the
alloted time. Trig functions can be messy. I'd suggest getting
a development board and timing things. (If you might buy a million,
the FEs will be helpful. If not...)
Why do you think you need floating point? The input isn't floating.
The output isn't floating.
As a (probably crazy) straw-man, you could consider table lookup.
It doesn't take much time, but it sure eats memory. It might be
worthwhile to implement the algorithim on a PC and look at it on
a graph. Can you compress that graph? Think interpolation,
or curve fitting. A cheap CPU with external memory might be less
expensive than a CPU fast enough to do the trig functions.
--
These are my opinions, not necessarily my employer's. I hate spam. |
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| Jan Panteltje... |
| Posted: Mon Oct 26, 2009 6:41 am |
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Guest
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On a sunny day (Sun, 25 Oct 2009 19:46:54 -0700 (PDT)) it happened Fred
<frederick.brown at (no spam) gmail.com> wrote in
<2c03acbb-9d7a-45b6-adc8-2e6924b1ff87 at (no spam) b18g2000vbl.googlegroups.com>:
[quote]I was wondering what DSP chip would be appropriate for a guitar pedal
effect. I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result.
[/quote]
Whatever you choose, keep in mind that digital processing introduces delays.
'Latency' is the word.
That may cause very undesirable effects in the end result.
So a bleeding fast DSP should be at an advantage here (read power guzzling).
Or maybe do some of the processing in hardware, say use an FPGA.
Depends on all you want to do.
Maybe an analog circuit makes more sense for a guitar...
But then again if your name or preference in Jimmy Hendrix., maybe all the artefacts will help a bit 
grin |
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| Tim Wescott... |
| Posted: Mon Oct 26, 2009 8:18 am |
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Guest
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On Sun, 25 Oct 2009 20:26:21 -0700, Fred wrote:
[quote]On Oct 25, 11:08 pm, "mook johnson" <m... at (no spam) mook.net> wrote:
"Fred" <frederick.br... at (no spam) gmail.com> wrote in message
news:2c03acbb-9d7a-45b6-
adc8-2e6924b1ff87 at (no spam) b18g2000vbl.googlegroups.com...
I was wondering what DSP chip would be appropriate for a guitar pedal
effect. I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result.
How simple is simple? A number of devices can do that. If you care
about audio quality I wouldn't use the build int ADCs and DACs though.
The function will be floating point and contain trig functions. Each
sample is run through the function once and outputed.
ADC and DAC convertion will need to either be contained in the chip or
sorted out separately.
I understand there are PICs out there and other similar things that can
do this, I'm just unfamiliar with there devices and trying to wade
though the websites to figure out what would work is kinda rough when
your clueless. :)
Fred
[/quote]
Floating point at 100kHz? Ick!
If you must do this with floating point you'll need a floating-point DSP
chip like an Analog Devices Sharc or a TI 6000 series ($$$, but maybe not
too much of a differential for a one-off). I'd see if I couldn't do this
with a fixed-point chip and some sort of approximation, or clever fixed-
point math. The design work is harder, but it may be worth it.
--
www.wescottdesign.com |
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| Vladimir Vassilevsky... |
| Posted: Mon Oct 26, 2009 8:36 am |
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Guest
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Fred wrote:
[quote]I was wondering what DSP chip would be appropriate for a guitar pedal
effect. I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result.
[/quote]
I am going to build Space Shuttle. It uses diodes. Would 1N5404 be a
good diode for Space Shuttle?
VLV |
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| ChrisQ... |
| Posted: Mon Oct 26, 2009 9:50 am |
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Fred wrote:
[quote]
I need to look at the different ways possible to do this, and hardware
to implement it.
Cordic looks interesting, I still need to figure out how to get the
ADC and DAC conversion done and the chip to run the function,
I also need to be able to have one user variable parameter a setting
knob that the the micro-controller would track in real time.along with
the input signal.
[/quote]
A lookup table for sin / cos is much faster and may allow the use of a
cheap micro, rather than a dsp and you can generate the table with a
page of C utility.
You only need to store one quadrant, so a 16k x 16 bit table gives
16bits + sign sin() or cos() function. 32 Kbytes of rom space...
Regards,
Chris |
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| ChrisQ... |
| Posted: Mon Oct 26, 2009 9:56 am |
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Vladimir Vassilevsky wrote:
[quote]
I am going to build Space Shuttle. It uses diodes. Would 1N5404 be a
good diode for Space Shuttle?
[/quote]
No, a 1N3712 would be *far* better for traveling through time and space,
especially if you encounter wormholes along the way ...
Regards,
Chris |
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| ChrisQ... |
| Posted: Mon Oct 26, 2009 10:07 am |
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Fred wrote:
[quote]
I need to look at the different ways possible to do this, and hardware
to implement it.
Cordic looks interesting, I still need to figure out how to get the
ADC and DAC conversion done and the chip to run the function,
I also need to be able to have one user variable parameter a setting
knob that the the micro-controller would track in real time.along with
the input signal.
[/quote]
The other point being avoidance of floating point and do it in fixed
point if at all possible. If you use a cheap micro, fp will be too much
of a performance hog with many C libraries, not to mention the amount of
code space it takes up...
Regards,
Chris |
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| Frank Buss... |
| Posted: Mon Oct 26, 2009 10:33 am |
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ChrisQ wrote:
[quote]The other point being avoidance of floating point and do it in fixed
point if at all possible. If you use a cheap micro, fp will be too much
of a performance hog with many C libraries, not to mention the amount of
code space it takes up...
[/quote]
Maybe you can attach an old 80287 to a microcontroller, there are still
some cheap ones at eBay:
http://tinyurl.com/80287-ebay
Many years ago I had to choose to add more RAM or a FPU chip to an Intel
80386 based computer. I decided to add 2 MB RAM, which was great, because
then Windows 3 worked :-)
--
Frank Buss, fb at (no spam) frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de |
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| Fred... |
| Posted: Mon Oct 26, 2009 10:42 am |
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OK guys,
The floating point math is a moot, now that I have been introduced to
CORDIC.
Futhermore even that is moot now that I just found the FV-1 by
SpinSemi.com It includes ADC and DAC on the die. It looks like just
what I want.
I'm off to investigate further... |
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| Tim Wescott... |
| Posted: Mon Oct 26, 2009 11:58 am |
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Guest
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On Sun, 25 Oct 2009 21:17:51 -0700, miso at (no spam) sushi.com wrote:
[quote]On Oct 25, 9:04Â pm, hal-use... at (no spam) ip-64-139-1-69.sjc.megapath.net (Hal
Murray) wrote:
In article
ae3a0936-286a-4a0f-9830-42a5ddf52... at (no spam) e18g2000vbe.googlegroups.com>,
 Fred <frederick.br... at (no spam) gmail.com> writes:
On Oct 25, 11:08 pm, "mook johnson" <m... at (no spam) mook.net> wrote:
"Fred" <frederick.br... at (no spam) gmail.com> wrote in message
news:2c03acbb-9d7a-45b6-
adc8-2e6924b1ff87 at (no spam) b18g2000vbl.googlegroups.com...
I was wondering what DSP chip would be appropriate for a guitar
pedal
effect. Â I need to sample the incoming signal preferably at 96kHz
perform a simple numeric function upon each sample and output he
result.
How simple is simple? Â A number of devices can do that. Â If you care
about audio quality I wouldn't use the build int ADCs and DACs
though.
The function will be floating point and contain trig functions. Â Each
sample is run through the function once and outputed.
ADC and DAC convertion will need to either be contained in the chip or
sorted out separately.
I understand there are PICs out there and other similar things that
can do this, I'm just unfamiliar with there devices and trying to wade
though the websites to figure out what would work is kinda rough when
your clueless. Â :)
Are you going to build one or a million? Â If the latter, the cost of
the silicon is important. Â If you only build a few, the silicon is
free. The expense is the time to develop the software so you should
look for an software environment you like.
You said 96kHz. Â Call that 100 kHz, or 10 microseconds per sample. You
need a CPU that is fast enough to run your algorithim in the alloted
time. Â Trig functions can be messy. Â I'd suggest getting a development
board and timing things. Â (If you might buy a million, the FEs will be
helpful. Â If not...)
Why do you think you need floating point? Â The input isn't floating.
The output isn't floating.
As a (probably crazy) straw-man, you could consider table lookup. It
doesn't take much time, but it sure eats memory. Â It might be
worthwhile to implement the algorithim on a PC and look at it on a
graph. Â Can you compress that graph? Â Think interpolation, or curve
fitting. Â A cheap CPU with external memory might be less expensive than
a CPU fast enough to do the trig functions.
--
These are my opinions, not necessarily my employer's. Â I hate spam.
Coordic.
[/quote]
Dunno about cordic -- to get that kind of speed from an inexpensive DSP
you probably need to go with something like a polynomial best-fit. This
would make the "knob" adjustment easy, as you'd just change the
coefficients of the polynomial.
--
www.wescottdesign.com |
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