Chip with simple program for Toy

[Ben Bradley]

On Sat, 21 Jun 2008 22:05:32 -0700, "BobW"
<nimby_NEEDSPAM@roadrunner.com> wrote:

You should seek some professional help for your design and/or take a class
in high-speed signal integrity.

At the very minimum, get this book, and pay for the fastest
shipping so you can hurry and get started reading it:
High Speed Digital Design: A Handbook of Black Magic
http://www.amazon.com/High-Speed-Digital-Design-Semiconductor/dp/0133957241
Much of this book is about board layout, and exactly this sort of
thing.

Bob

 

[Rube Bumpkin]

Talal Itani wrote:

Hello,

At work we have an Intronix Logicport PC based logic analyzer. It is good,
I like using it, but it has very little memory (2048 samples). Can you
recommend something?

Thanks,
T.I.

Have a look at the Agilent 1690 series. It has the same triggering and
GUI as the rest of Agilent LA's, connecting to the PC through FireWire.
The cheapest is the 1693A, 34 channels, 200 MHz state, 400/800MHz
Timing, 1M depth.
The link is long and ugly, so go to www.agilent.com and type 1693A in
the search field on the right.

RB

 

[Joerg]

Paul Keinanen wrote:

On Sat, 21 Jun 2008 15:25:38 -0700 (PDT), bill.sloman@ieee.org wrote:

On Jun 22, 5:52 am, Paul Keinanen <keina...@sci.fi> wrote:

Are you sure that these are ordinary inductors or just a wire through
a ferrite bead?

While the ferrite will increase the inductance, a suitable ferrite
material is also quite lossy at higher frequencies, reducing the risk
for unwanted resonances with the capacitors.
Sadly, you can't rely on this. I've had to put little resistors in
series with ferrite bead to kill a resonance - admittedly at a few
hundred kHz, where the bead doesn't look that lossy.

It would be quite hard to find material that would be lossy at such
low frequencies. For instance materials listed at
http://www.fair-rite.com/newfair/materials.htm start at 1 MHz
(material 31), while the common material 73 have significant losses
only above 10 MHz.

I am lossy at low frequencies. Met my wife at an ultrasound company and
she was quited stunned that my body would absorb even 3.5MHz to the
point where she couldn't get a decent ultrasound image. Never seen it
this bad before. She married me anyway.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

On Jun 22, 8:01 am, "Talal Itani" <tit...@verizon.net> wrote:

Hello,

Somebody recommended a Rigol mixed signal oscilloscope. I checked the Rigol
website. Do you know anything about this company, these scopes? Thanks.http://www.rigolna.com/products_oscilloscopes.aspx

T.I.

They are not bad. Actually I find them to be good value for the money.
email them, they will gladly send you a demo unit.

 

[Vladimir Vassilevsky]

Tim Wescott wrote:

WHAT? You mean that semiconductor companies hire kids with no real
experience fresh out of college to be applications engineers?

Don't you know? Those who can't be the real engineers take the position
of the application engineers.

Now THAT would imply that they look at their applications engineers as a
marketing expense, not a profit center.

Of course they are. Application engoneer is a sales position.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

 

[rickman]

If you are going to layout the board yourself, then you need to learn
good board design techniques. Even if you let someone else layout the
board, you should be the one telling them what to do, not the other
way around. To do otherwise can result in a board that does not work
because of power decoupling and SI issues.

The inductors on this design are pretty bizarre and are likely not
even used on the real board. A 50 uH inductor is rather large and
using 15 of them would stick out like a sore thumb. I expect they
were replaced in production with 0 ohm jumpers. In general, inductors
are not needed for power supplies. Good ground planes do an excellent
job of minimizing high frequency noise. Low frequency noise is
another issue however. I used a CP Clare part once that had 0 dB
PSRR. They didn't put that in the data sheet, they let you figure it
out on your own. My analog power rail was derived from the digital
power rail and had 10 mV of 300 Hz noise from a control loop in the
DSP. The 10 mV of noise coupled directly onto the phone line and
showed up as a low level, but very distinct hum or buzz.

0 dB of PSRR is unusual in a chip of any sort (I have to take my hat
off to CP Clare). But the point is that you need to include the right
capacitance to handle noise at all frequencies. By preventing the
noise in the first place, you don't have to worry about it coupling
into other circuits.

Rick

Rick

On Jun 21, 7:43 pm, "Talal Itani" <tit...@verizon.net> wrote:

What if we are not sensible about the layout? Meaning, I layout the board
myself.

The DSP is a TI F2808. The schematics I was referring to are here
http://www.ti.com/litv/zip/sprr098. It is a zip file. Once you unzip
the file, 2 pdf files appear. The larger file has the schematics I am
referring to. The inductors are at the top-left corner of the screen.

This mediocre design is obviously made by a superstitious and
unexperienced person. There are several things in the schematics that
should be done differently. No wonder that at some time ago the designer
had burned with the EMC, and after that he sticks the inductors
everywhere. The value of 50uH is ridiculous. Never mind those inductors;
with the sensible layout the F28xx doesn't need them.

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

 

[Vladimir Vassilevsky]

MK wrote:

I designed a board with an 'F2808 about 2 years ago. Based on TI app notes I
put 100nH in series with the two ADC power pins only and 2uF to ground on
each (2 * 0603 caps - different values).

Was it necessary - I don't know - never tried it without.

Did the ADC work - yes - I was impressed at how well it worked.

The internal ADC of TI 28xx is crap. It has tremendously inacurate
internal reference and high zero offset. With 12 bits available, the
true accuracy is about 8 bits unless you have the ADC calibrated.

The board was 4 layers with careful design of gorund planes/fills around the
processor and decoupling caps on both sides.

There is no need for 4 layer board with 28xx. The layout can be done on
two layers just fine. Been there, done that.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

 

[Vladimir Vassilevsky]

Talal Itani wrote:

What if we are not sensible about the layout? Meaning, I layout the board
myself.

If you are not sensible about the layout, then God help you.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

The DSP is a TI F2808. The schematics I was referring to are here
http://www.ti.com/litv/zip/sprr098. It is a zip file. Once you unzip
the file, 2 pdf files appear. The larger file has the schematics I am
referring to. The inductors are at the top-left corner of the screen.


This mediocre design is obviously made by a superstitious and
unexperienced person. There are several things in the schematics that
should be done differently. No wonder that at some time ago the designer
had burned with the EMC, and after that he sticks the inductors
everywhere. The value of 50uH is ridiculous. Never mind those inductors;
with the sensible layout the F28xx doesn't need them.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

 

[Vladimir Vassilevsky]

rickman wrote:

If you are going to layout the board yourself, then you need to learn
good board design techniques. Even if you let someone else layout the
board, you should be the one telling them what to do, not the other
way around. To do otherwise can result in a board that does not work
because of power decoupling and SI issues.

It is not a big deal to lay out the board for TMS28xx. Two layers work
fine. With 28xx, the very important thing is the power sequensing on
startup and shutdown.

The inductors on this design are pretty bizarre and are likely not
even used on the real board.

Indeed. Especially as the power pins of the chip are supposed to be
connected directly.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

 

[Jamie]

Bob Monsen wrote:

"Talal Itani" <titani@verizon.net> wrote in message
news:6zk7k.871$9J.437@trnddc06...


One model that I have used is this one:
http://www.dynoninstruments.com/products_elab080.php
It's a DSO, logic analyzer, and waveform generator all in one.
It's only 80 MS/s but for $500 you can't expect much more. I've
actually found
myself using the digital waveform generators on this thing quite often.


Thanks, this is nice, yet I wished it had a higher sampling rate. Are
you aware of any others?



I have a SDS 200A from softDSP. The windows software is crap. The FFT
feature is basically unusable. The triggering is unreliable. The claim
of a 200MHz bandwidth is blather, they do 'statistical sampling', which
is basically adding in some random jitter to the sample clock and
correlating it somehow.

OTOH, the unit is small enough to go with your laptop in the same case,
and is useful therefore as an onsite scope. It can store a fairly large
buffer, and allows the possibility of doing things like line monitoring
with a very slow signal (like 1s per division).

It was also very cheap, less than $1k.

I'm not sure I'd buy it again. It does have an SDK (for $200 extra) that
allows the possibility of doing special kinds of monitoring with a
custom display.

$0.02

Regards,
Bob Monsen

In other words, it's a paper weight to be used at the site as things are

blowing around!


http://webpages.charter.net/jamie_5"

 

[Terry Given]

Tim Wescott wrote:

Joerg wrote:

Tim Wescott wrote:

Talal Itani wrote:

Hello,

I was looking at the schematics for a DSP-based board, running at
100 MHz. They have a tiny inductor with every bypass cap around the
DSP. Do you think this is necessary? This DSP has analog stuff
built-in. If we do not need analog, can the inductors be eliminated?

Thanks,
T.I.

Search for newsgroup postings with "Jeorg" and "ground" or
"grounding" in them.

You'll get a load of (AFAIK) good opinions.


Thanks for the kudos. It would have to be "Joerg" though. Sometimes I
wish I had an easier name.

'O' before 'E' unless I'm at sea?

Dunno why I can't keep it straight.


Inductors in series with the caps would tend to isolate the power
supply from noise in the DSP, but it would also create a bunch of odd
resonances. It's not how I'd want to isolate a power supply from a
chip.


It will become really interesting when the DSP exhibits a somewhat
burst-like load behavior. On the scope it'll look like Dolphins
frolicking in the ocean.

That's kinda what I thought. Plus I see no reason to do each power line
individually, and some good reasons not to (Different versions of VDD at
different points in the circuit, oh boy!).

they are also probably ferrite beads, rather than inductors per se. but
I have corrected a few designs where the "engineers" really did use
inductors. nasty little bobbin core things. yuk!

I've seen quite a few app notes with FBs liberally sprinkled everywhere.
I presume this is because its easier than thinking. that being said, I
have a design thats soon to undergo EMC testing where I have exactly
followed the manufacturers recommendations for the FPGA & HY ships, but
I plan on muntzing most of the FBs during a day at the EMC lab. odds on
I can leave ALL of them off...

Cheers
Terry

 

On Jun 23, 6:46 am, Joerg <notthisjoerg...@removethispacbell.net>
wrote:

Paul Keinanen wrote:
On Sat, 21 Jun 2008 15:25:38 -0700 (PDT), bill.slo...@ieee.org wrote:

On Jun 22, 5:52 am, Paul Keinanen <keina...@sci.fi> wrote:

Are you sure that these are ordinary inductors or just a wire through
a ferrite bead?

While the ferrite will increase the inductance, a suitable ferrite
material is also quite lossy at higher frequencies, reducing the risk
for unwanted resonances with the capacitors.
Sadly, you can't rely on this. I've had to put little resistors in
series with ferrite bead to kill a resonance - admittedly at a few
hundred kHz, where the bead doesn't look that lossy.

It would be quite hard to find material that would be lossy at such
low frequencies. For instance materials listed at
http://www.fair-rite.com/newfair/materials.htmstart at 1 MHz
(material 31), while the common material 73 have significant losses
only above 10 MHz.

I am lossy at low frequencies. Met my wife at an ultrasound company and
she was quited stunned that my body would absorb even 3.5MHz to the
point where she couldn't get a decent ultrasound image. Never seen it
this bad before. She married me anyway.

One of my colleagues in the ultrasound group at EMI was a rower with
lots of muscle around the trunk - made him a lousy test subject for
ultrasound imaging. I played field hockey, which mainly builds up the
running muscles, and was much more transparent.

--
Bill Sloman, Nijmegen

 

[David L. Jones]

On Jun 23, 9:58 am, "Talal Itani" <tit...@verizon.net> wrote:

Talal
You are running around like a headless chook!
Do you even *know* the budget your company has set for you to buy this
oscilloscope/logic analyser?
You *need* to know that, so find out and then tell us so we can help you.

You said your boss asked you to buy this scope. Does he/she have *any*
idea of the specs required, or are you free to suggest something yourself
?

Yes, Rigol are pretty good as far as a low end Chinese designed and made
scope goes. Agilent rebadge them under their own brand name (3000 series),
so they must be pretty confident in the design and manufacture quality
plus the firmware stability.

Yes, I am running like a headless chook, untill I know what we need, what is
out there, what our budget is. So, it is ok to ask all sorts of questions,
even before knowing what we really need.

Fair enough, I know what it's like not being able to get management to
commit to anything!
I've lot count of the number of times they agree "we need one of
these" and then I get a quote and they say there is no budget for it.
Management will happily blow $100,000 on some production jig, but
won't fork out for a $50 multimeter.

In this case its often best to shoot for low price, you stand a better
chance of at least getting something for your lab!

Are Rigol much cheaper than the brand names?

Yes.
Rigol and Instek(Goodwill) are the two big "cheap professional"
brands.
You get a lot of value for your dollar with those brands. Shop around
too, prices vary. Use Froogle (http://www.google.com/products) to find
comparative prices.

The exact same Rigol scope is more expensive when you buy it from
Agilent.

Dave.

 

[Robert Baer]

Talal Itani wrote:

"Robert Baer" <robertbaer@localnet.com> wrote in message
newsSdnXt4z_WBlsPVnZ2dnUVZ_gadnZ2d@posted.localnet...

Talal Itani wrote:

Hello,

I need to have a 4-layer board made, a prototype, 2 boards, nothing
fancy. I did some research in this newsgroup and I narrowed it down to
Sierra Pro Express, ExpressPCB, and AC Advanced Circuits. Do you think I
made the right choice? Do you have any recommendations? I would like to
receive the board 3-5 days.

T.I.

One usually has to pay a premium for anything less than 10 days, and
certainly for 3 days.
Besids, transportation will take anywhere from 2 days to 5 days (total
turn-around time).
Are you Russian?



No.


The Q was "why the rush"?

 

[Robert Baer]

Joerg wrote:

Robert Baer wrote:

Joerg wrote:

Talal Itani wrote:

Can ExpressPCB receive files from other PCB software?


I've had good experiences with Advanced Circuits (http://www.
4pcb.com/). Make sure to use their free FDM service
(http://www.freedfm.com/), even if you don't end up going with them
for
manufacturing.

ExpressPCB is only good for quick-and-dirty stuff. Their advantage is
that they're cheap and their design software is pretty simple to use,
but the big disadvantage is that it locks you in to their software.
Also I've never done 4-layer stuff with them; I believe they're also
kind of limited in that department. They're great for quick-and-dirty
stuff though.

Regards,
-- Hauke D

On Jun 21, 4:19 pm, "Talal Itani" <tit...@verizon.net> wrote:



Hello,
I need to have a 4-layer board made, a prototype, 2 boards,
nothing fancy.
I did some research in this newsgroup and I narrowed it down to
Sierra Pro
Express, ExpressPCB, and AC Advanced Circuits. ?Do you think I
made the
right choice? ?Do you have any recommendations? ?I would like to
receive the
board 3-5 days.
T.I.- Hide quoted text -


- Show quoted text -



I've used ExpressPCB for small projects before, but always 2-layer
stuff.
I've never had a problem with them, or their boards.

As for being "locked-in" to their software, for an extra $60 (last
time I checked), they will send you the Gerber files. From there, you
can import to many of the other programs avail.


Then if you need to make a little change it'll be another $60?


Also, I recall hearing a while ago that a lot of these PCB prototype
houses are all built at the same place anyway. So, while you might
see 10 different company names (i.e., resellers), the boards
themselves all come from the same place. Sorry, I don't remember the
names of the companies involved, and don't know whether ExpressPCB is
one of them.


I have also used 4PCB, quite happy so far. They only messed up once
(unapproved Gerber edits) but made good on that with an additional
fast run, on the house. The nice thing is that I always have a real
contact person there. She really helped us when they defaulted to
this dreaded RoHS process which we absolutely did not want.

Not much differnce between tin/lead solder on pads and silver plate
*IF* one is not going above (say) 150C.
Tin/lead solder and tin/silver solders act esentially the same, so
what is the beef?



Non-RoHS parts on a RoHS PCB usually isn't a good idea.

Give at least one good reason...

 

[René]

On Sun, 22 Jun 2008 08:23:43 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

For regular digital/embedded stuff, on a 100 MHz scope, any probe will
work. When the fuzzies start to matter, a good fet probe is magical.

Depends on the hardware on hand, I have found (not the easy way, I
might add , that the act of putting a std probe on a wayward adress
/ data line, changes the conditions enough to make the measurement
invalid.
Sometimes the fault does not occur with the probe in place (which in
it self tells you something), sometimes the device stops working
completely.

Or all seems OK. But when the probe is removed, the system crashes
after 5 minutes..

I had good results with the 1K resistive low cap probe, showing
artefacts <100 MHz the std probe would not reveal.
(spikes, shoot troughs, oscillations etc.)

A good fet probe is nice to have, but IMHO the 1K probe was almost as
good. (with *very* short ground lead off course)

And as everybody surely knows here - to resolve a 100 MHz artefact,
one needs as scope with BW magnitudes higher.

--
- René

 

[JosephKK]

On Mon, 23 Jun 2008 13:14:57 +1200, Terry Given <my_name@ieee.org>
wrote:

Tim Wescott wrote:
Joerg wrote:

Tim Wescott wrote:

Talal Itani wrote:

Hello,

I was looking at the schematics for a DSP-based board, running at
100 MHz. They have a tiny inductor with every bypass cap around the
DSP. Do you think this is necessary? This DSP has analog stuff
built-in. If we do not need analog, can the inductors be eliminated?

Thanks,
T.I.

Search for newsgroup postings with "Jeorg" and "ground" or
"grounding" in them.

You'll get a load of (AFAIK) good opinions.


Thanks for the kudos. It would have to be "Joerg" though. Sometimes I
wish I had an easier name.

'O' before 'E' unless I'm at sea?

Dunno why I can't keep it straight.


Inductors in series with the caps would tend to isolate the power
supply from noise in the DSP, but it would also create a bunch of odd
resonances. It's not how I'd want to isolate a power supply from a
chip.


It will become really interesting when the DSP exhibits a somewhat
burst-like load behavior. On the scope it'll look like Dolphins
frolicking in the ocean.

That's kinda what I thought. Plus I see no reason to do each power line
individually, and some good reasons not to (Different versions of VDD at
different points in the circuit, oh boy!).


they are also probably ferrite beads, rather than inductors per se. but
I have corrected a few designs where the "engineers" really did use
inductors. nasty little bobbin core things. yuk!

I've seen quite a few app notes with FBs liberally sprinkled everywhere.
I presume this is because its easier than thinking. that being said, I
have a design thats soon to undergo EMC testing where I have exactly
followed the manufacturers recommendations for the FPGA & HY ships, but
I plan on muntzing most of the FBs during a day at the EMC lab. odds on
I can leave ALL of them off...

Cheers
Terry

Mad man Muntz must be spinning in his grave.

 

[logicgeek]

On Jun 22, 10:25 pm, Rube Bumpkin <Some...@somewhere.world> wrote:

Talal Itani wrote:
Hello,

At work we have an Intronix Logicport PC basedlogic analyzer.  It is good,
I like using it, but it has very little memory (2048 samples).  Can you
recommend something?

Thanks,
T.I.

Have a look at the Agilent 1690 series. It has the same triggering and
GUI as the rest of Agilent LA's, connecting to the PC through FireWire.
The cheapest is the 1693A, 34 channels, 200 MHz state, 400/800MHz
Timing, 1M depth.
The link is long and ugly, so go towww.agilent.com and type 1693A in
the search field on the right.

RB

Also have a look at the La-Gold-36 or Logic-16 from Janatek. The Gold
samples at 1Ghz and has a mem depth of 1Meg per channel.
www.janatek.com

G

 

[Klaus Kragelund]

On 21 Jun., 20:11, n...@puntnl.niks (Nico Coesel) wrote:

"Talal Itani" <tit...@verizon.net> wrote:
Hello,

My company wants to buy an oscilloscope.  The scope that meets our needs is
around $7,000.  I am sure we can save much money if we buy a PC-based unit,
like Picoscope.  Do you have experience with PC based scopes?  Do you
recommend them for serious work?

I've used Picoscope but I think they are crappy. There is no
peak-detection which makes high frequency signals dissapear at low
sweep rates. The number of sweeps (screen updates) is around 3 or 4
per second. Way too slow. And their software crashes every now and
then.

--
Programmeren in Almere?
E-mail naar nico@nctdevpuntnl (punt=.)

I have also used the PicoScopes. The update is not as the other poster
says, I think I have like at least 50 times per second.( on a USB 1.0
connection)

That being said, some of the SW is buggy. But I live with that. The
great thing is that my 12bit scope can be programmed and I can then
use it for a test system also and even better when it is connected to
the PC the documentation of measurements are a charm.

Also the FFT is quite good

Regards

Klaus

 

[hrh1818]

On Jun 22, 7:07 pm, "Talal Itani" <tit...@verizon.net> wrote:

Are Rigol much cheaper than the brand names?

Talal,

Are you doing any research on your own or are you just being lazy? You're
not going to get much help if you just post whatever comes into your head.

Bob
--

Well, my friend, sure, I can find the information elsewhere, on google, in
the library, at work. Yet I love to post messages and hear from experts,
and most are eager to help. So, why not!

One short cut for finding information from different manufacturers of
logic analyzers and storage scopes is Ebay. Enter a phrase like logic
analyzer in the search field. You will then get a lot of hits and a
surprising amount of information about each product offered.

Howaard