Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.

Also, just out of curiosity, how many of you do your own PCB layout,
versus farming it out? It would certainly save us a lot of money to
buy the tools and do it ourselves, but it seems like laying out a
board out well requires quite a bit of experience, especially a 6-8
layer board with high pin count FPGA's.

We're just setting up a hardware shop here, and although I've been
doing FPGA and board schematics design for a while, it's always been
at a larger company with resources to farm the layout out, and we
never did anything high-speed to really worry about the board layout
too much. Thanks in advance for your opinions.

Dave

"Joerg" <notthisjoerg...@removethispacbell.net> wrote in message

news:U5MNj.6956$GE1.6193@nlpi061.nbdc.sbc.com...



qrk wrote:
On Thu, 17 Apr 2008 09:43:09 -0700 (PDT), Dave <dhsch...@gmail.com
wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.

Also, just out of curiosity, how many of you do your own PCB layout,
versus farming it out? It would certainly save us a lot of money to
buy the tools and do it ourselves, but it seems like laying out a
board out well requires quite a bit of experience, especially a 6-8
layer board with high pin count FPGA's.

We're just setting up a hardware shop here, and although I've been
doing FPGA and board schematics design for a while, it's always been
at a larger company with resources to farm the layout out, and we
never did anything high-speed to really worry about the board layout
too much. Thanks in advance for your opinions.

Dave

Sure wish there was a slick way of doing FPGA pinouts. I usually use
graph paper and figure out the FPGA pinout to other parts to minimize
routing snarls.

I do pcb layouts on my own and other folks designs. Our boards have
high-speed routing, switching power supplies, and high-gain analog
stuff; sometimes all on the same board. Unless the service bureau has
someone who understands how to lay out such circuitry and place
sensitive analog stuff near digital junk, it is more trouble to farm
out than do it yourself if you want the board to work on the first
cut.

Or find a good layouter and develop a long-term business relationship. My
layouter knows just from looking at a schematic which areas are critical.
He's a lot older than I am and that is probably one of the reasons why his
stuff works without much assistance from me. Nothing can replace a few
decades of experience.

Doing your own layout will take a lot of learning to master the PCB
layout program and what your board vendor can handle. It will take 5
to 10 complicated boards to become mildly proficient at layout. I
don't know about saving cost. Your time may be better spent doing
other activities rather than learning about layout and doing the
layouts. ...

Yep, that's why I usually do not do my own layouts. Occassionally I route
a small portion of a circuit and send that to my layouter. No DRC or
anything, just to show him how I'd like it done.

... The upside to doing your own layout - you control the whole
design from start to finish. If you have a challenging layout, you'll
have a much higher probability of having a working board on the first
try which has hidden savings (getting to market earlier <- less
troubleshooting + less respins).

---
Mark

--
Regards, Joerg

http://www.analogconsultants.com/

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

I agree with Joerg. Good high speed or mixed signal PCB layout is a career
choice, and we electrical engineers already chose our career. A good layout
requires someone who understands not just the software package, but the
details of how the manufacturing operation is going to proceed, what the
limits of the processes are, what the assembly operations require of the
board, and is anal about things like footprint libraries and solder mask
clearances and a thousand other details that I'm only partially aware of.
The more complex your design, the more critical these things become.

I have two good local outfits for farming out boards. For complex stuff,
they know I'll come to their place and sit next to the designer for a good
bit of the initial placement. While we are doing placement, we are also
discussing critical nets, routing paths, layer usage, etc. That gives us
direct face to face communication and avoids spending lots of time trying to
write/draw everything in gory detail (which gets ignored or misunderstood a
lot of the time). That investment pays big dividends in schedule and board
performance.

Don't be fooled by the relatively low cost of the software. That's not where
the big costs are.

I once laid off my entire PCB layout department and sent all the work
outside, because although my employees all knew how to use the software,
none of them could tell me what their completion date would be, or how many
hours it would take, and they certainly weren't interested in meeting
schedules. The outside sources would commit to a cost and a delivery date.
And we already knew they could meet our performance objectives. Fixed price
contracts are great motivators. Missing an engineering test window, or
slipping a production schedule because of a layout delay can be enormously
expensive.

Of course, if I had let my engineers do their own layouts, the motivation
would have been present, but the technical proficiency would not. How
proficient can anyone become if they only do layout a few times a year?
Also, on many projects engineers use the layout period for other important
things like documentation, test procedures, writing test code, etc. Doing
your own layout serializes these tasks and will stretch your schedule.

So my advice is to keep doing what you have been doing. Its far more likely
that its the cheapest approach, even though you occasionally have to write a
big check.

Steve

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.

Also, just out of curiosity, how many of you do your own PCB layout,
versus farming it out? It would certainly save us a lot of money to
buy the tools and do it ourselves, but it seems like laying out a
board out well requires quite a bit of experience, especially a 6-8
layer board with high pin count FPGA's.

We're just setting up a hardware shop here, and although I've been
doing FPGA and board schematics design for a while, it's always been
at a larger company with resources to farm the layout out, and we
never did anything high-speed to really worry about the board layout
too much. Thanks in advance for your opinions.

Dave

On Thu, 17 Apr 2008 09:43:09 -0700 (PDT), Dave <dhschetz@gmail.com
wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.

Also, just out of curiosity, how many of you do your own PCB layout,
versus farming it out? It would certainly save us a lot of money to
buy the tools and do it ourselves, but it seems like laying out a
board out well requires quite a bit of experience, especially a 6-8
layer board with high pin count FPGA's.

We're just setting up a hardware shop here, and although I've been
doing FPGA and board schematics design for a while, it's always been
at a larger company with resources to farm the layout out, and we
never did anything high-speed to really worry about the board layout
too much. Thanks in advance for your opinions.

Dave

Sure wish there was a slick way of doing FPGA pinouts. I usually use
graph paper and figure out the FPGA pinout to other parts to minimize
routing snarls.

I do pcb layouts on my own and other folks designs. Our boards have
high-speed routing, switching power supplies, and high-gain analog
stuff; sometimes all on the same board. Unless the service bureau has
someone who understands how to lay out such circuitry and place
sensitive analog stuff near digital junk, it is more trouble to farm
out than do it yourself if you want the board to work on the first
cut.

Doing your own layout will take a lot of learning to master the PCB
layout program and what your board vendor can handle. It will take 5
to 10 complicated boards to become mildly proficient at layout. I
don't know about saving cost. Your time may be better spent doing
other activities rather than learning about layout and doing the
layouts. ...

... The upside to doing your own layout - you control the whole
design from start to finish. If you have a challenging layout, you'll
have a much higher probability of having a working board on the first
try which has hidden savings (getting to market earlier <- less
troubleshooting + less respins).

---
Mark

qrk wrote:
On Thu, 17 Apr 2008 09:43:09 -0700 (PDT), Dave <dhschetz@gmail.com
wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.

Also, just out of curiosity, how many of you do your own PCB layout,
versus farming it out? It would certainly save us a lot of money to
buy the tools and do it ourselves, but it seems like laying out a
board out well requires quite a bit of experience, especially a 6-8
layer board with high pin count FPGA's.

We're just setting up a hardware shop here, and although I've been
doing FPGA and board schematics design for a while, it's always been
at a larger company with resources to farm the layout out, and we
never did anything high-speed to really worry about the board layout
too much. Thanks in advance for your opinions.

Dave

Sure wish there was a slick way of doing FPGA pinouts. I usually use
graph paper and figure out the FPGA pinout to other parts to minimize
routing snarls.

I do pcb layouts on my own and other folks designs. Our boards have
high-speed routing, switching power supplies, and high-gain analog
stuff; sometimes all on the same board. Unless the service bureau has
someone who understands how to lay out such circuitry and place
sensitive analog stuff near digital junk, it is more trouble to farm
out than do it yourself if you want the board to work on the first
cut.


Or find a good layouter and develop a long-term business relationship. My
layouter knows just from looking at a schematic which areas are critical.
He's a lot older than I am and that is probably one of the reasons why his
stuff works without much assistance from me. Nothing can replace a few
decades of experience.


Doing your own layout will take a lot of learning to master the PCB
layout program and what your board vendor can handle. It will take 5
to 10 complicated boards to become mildly proficient at layout. I
don't know about saving cost. Your time may be better spent doing
other activities rather than learning about layout and doing the
layouts. ...


Yep, that's why I usually do not do my own layouts. Occassionally I route
a small portion of a circuit and send that to my layouter. No DRC or
anything, just to show him how I'd like it done.


... The upside to doing your own layout - you control the whole
design from start to finish. If you have a challenging layout, you'll
have a much higher probability of having a working board on the first
try which has hidden savings (getting to market earlier <- less
troubleshooting + less respins).

---
Mark


--
Regards, Joerg

http://www.analogconsultants.com/

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

I tend to agree with the 'farm-it-out' crowd. Unfortunately, my
current employer doesn't want to work with my previous layout people,
so I've been trying to search for a new partner. I've found plenty of
board fab and assembly places, but not so much on the layout. It made

The opinions
look pretty split from the replies here, maybe it comes down to how
many times you do a layout each year, and how much you enjoy that sort
of work. I definitely think it's something you have to do fairly often
to keep your chops up.

Andy, I'd also like to hear more about your pin-swap FPGA design flow
- what tools do that?

"Dave" <dhschetz@gmail.com> wrote in message
news:dfc27fc0-c07f-456c-80cb-b31e867dd253@d1g2000hsg.googlegroups.com...
The opinions
look pretty split from the replies here, maybe it comes down to how
many times you do a layout each year, and how much you enjoy that sort
of work. I definitely think it's something you have to do fairly often
to keep your chops up.

I think what you're seeing is that fact that, by sheer volume of products,
guys doing relatively low-speed digital stuff completely dominate those doing
very low-level analog, RF, microwave, or truly high-speed digital. In the
former case, it just doesn't really matter that much how you layout the board.
Sure, there are definitely better ways and worse ways, but even up to clock
rates pushing 100MHz, for digital stuff I think you can give a guy about an
hour of education and he'll be able to make boards work just fine.

Another point to keep in mind is that there's a significant difference between
being able to design a board well when you're talking relatively small volume
production for high-end commercial or military customers where you can afford
to just toss in some extra layers and pay for blind or buried vias or tigether
tolerances if you're at all unsure of how well your layout skills really are
vs. designing a complex board for highly cost-competitive mass-markets. The
later requires a lot of skills that are anything but what is commonly taught!
(E.g., typically at tech seminars you'll hear people preaching, "throw in a
ground plane!" -- an action that saves many an otherwise broken design, but
one which might not be possible if your competition has already figured out
how to live without one.)

Not anymore. Part of my daily bread is earned salvaging designs where
someone thought "Oh, it's just slow stuff". But it ain't grampa's old SN7400
anymore, today's logic chips are fast.

And don't split that plane. But yes, often one has to make do with two-layer
phenolic. That is often true art.

BTW does that little switcher work?

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:ZjRNj.9697$2g1.9469@nlpi068.nbdc.sbc.com...
Not anymore. Part of my daily bread is earned salvaging designs where
someone thought "Oh, it's just slow stuff". But it ain't grampa's old SN7400
anymore, today's logic chips are fast.

OK, ok, good point. Doesn't someone now have a logic family that's purposely
been slowed down due to this "problem?"

And don't split that plane. But yes, often one has to make do with two-layer
phenolic. That is often true art.

From Thomas Lee (Stanford) in "Planar Microwave Engineering":

In extremely low-cost consumer devices (e.g., toys, pocket radios, etc.), an
even less expensive board material is not infrequently encountered. Phenolic
is often a caramel brown, typically has an "organical chemical" odor, and is
remarkably lossy. Although phenolic is occasionally used for RF toys up to
100MHz, it is totally insuitable for serious applications. It is mentioned
here simply to answer the question: "What is that cheap, malodorous board made
of?"

:-)

I know, I know, he's living in an ivory tower a bit, but he is one smart
cookie.

BTW does that little switcher work?

I've had that board back for about a week, although I haven't actually tested
out the switcher yet since the DSP guy isn't interested in working with the
new (digital) board until the new RF board comes back (and gets tested) as
well, which is still a couple weeks out. (There's this "Big Tester Board"
that's needed to test the RF board and said BTB has spent something over a
week bouncing around engineering getting tweaked/fixed/etc... we'll be paying
a premium to actually get it fabbed in time to start testing RF boards at this
point, unfortunately .) I can and probably should just put a dummy load
on the switcher, turn it on, and see if there's any obvious problems before
the DSP guy starts looking at his clock jitter. Tomorrow sounds like a good
day for that...

On Apr 17, 5:13 pm, "Steve" <sjbur...@comcast.net> wrote:



"Joerg" <notthisjoerg...@removethispacbell.net> wrote in message

news:U5MNj.6956$GE1.6193@nlpi061.nbdc.sbc.com...

qrk wrote:
On Thu, 17 Apr 2008 09:43:09 -0700 (PDT), Dave <dhsch...@gmail.com
wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.

Also, just out of curiosity, how many of you do your own PCB layout,
versus farming it out? It would certainly save us a lot of money to
buy the tools and do it ourselves, but it seems like laying out a
board out well requires quite a bit of experience, especially a 6-8
layer board with high pin count FPGA's.

We're just setting up a hardware shop here, and although I've been
doing FPGA and board schematics design for a while, it's always been
at a larger company with resources to farm the layout out, and we
never did anything high-speed to really worry about the board layout
too much. Thanks in advance for your opinions.

Dave

Sure wish there was a slick way of doing FPGA pinouts. I usually use
graph paper and figure out the FPGA pinout to other parts to minimize
routing snarls.

I do pcb layouts on my own and other folks designs. Our boards have
high-speed routing, switching power supplies, and high-gain analog
stuff; sometimes all on the same board. Unless the service bureau has
someone who understands how to lay out such circuitry and place
sensitive analog stuff near digital junk, it is more trouble to farm
out than do it yourself if you want the board to work on the first
cut.

Or find a good layouter and develop a long-term business relationship. My
layouter knows just from looking at a schematic which areas are critical.
He's a lot older than I am and that is probably one of the reasons why his
stuff works without much assistance from me. Nothing can replace a few
decades of experience.

Doing your own layout will take a lot of learning to master the PCB
layout program and what your board vendor can handle. It will take 5
to 10 complicated boards to become mildly proficient at layout. I
don't know about saving cost. Your time may be better spent doing
other activities rather than learning about layout and doing the
layouts. ...

Yep, that's why I usually do not do my own layouts. Occassionally I route
a small portion of a circuit and send that to my layouter. No DRC or
anything, just to show him how I'd like it done.

... The upside to doing your own layout - you control the whole
design from start to finish. If you have a challenging layout, you'll
have a much higher probability of having a working board on the first
try which has hidden savings (getting to market earlier <- less
troubleshooting + less respins).

---
Mark

--
Regards, Joerg

http://www.analogconsultants.com/

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

I agree with Joerg. Good high speed or mixed signal PCB layout is a career
choice, and we electrical engineers already chose our career. A good layout
requires someone who understands not just the software package, but the
details of how the manufacturing operation is going to proceed, what the
limits of the processes are, what the assembly operations require of the
board, and is anal about things like footprint libraries and solder mask
clearances and a thousand other details that I'm only partially aware of.
The more complex your design, the more critical these things become.

I have two good local outfits for farming out boards. For complex stuff,
they know I'll come to their place and sit next to the designer for a good
bit of the initial placement. While we are doing placement, we are also
discussing critical nets, routing paths, layer usage, etc. That gives us
direct face to face communication and avoids spending lots of time trying to
write/draw everything in gory detail (which gets ignored or misunderstood a
lot of the time). That investment pays big dividends in schedule and board
performance.

Don't be fooled by the relatively low cost of the software. That's not where
the big costs are.

I once laid off my entire PCB layout department and sent all the work
outside, because although my employees all knew how to use the software,
none of them could tell me what their completion date would be, or how many
hours it would take, and they certainly weren't interested in meeting
schedules. The outside sources would commit to a cost and a delivery date.
And we already knew they could meet our performance objectives. Fixed price
contracts are great motivators. Missing an engineering test window, or
slipping a production schedule because of a layout delay can be enormously
expensive.

Of course, if I had let my engineers do their own layouts, the motivation
would have been present, but the technical proficiency would not. How
proficient can anyone become if they only do layout a few times a year?
Also, on many projects engineers use the layout period for other important
things like documentation, test procedures, writing test code, etc. Doing
your own layout serializes these tasks and will stretch your schedule.

So my advice is to keep doing what you have been doing. Its far more likely
that its the cheapest approach, even though you occasionally have to write a
big check.

Steve

I tend to agree with the 'farm-it-out' crowd. Unfortunately, my
current employer doesn't want to work with my previous layout people,
so I've been trying to search for a new partner. I've found plenty of
board fab and assembly places, but not so much on the layout. It made
me think that the rest of the world did their own layout. The opinions
look pretty split from the replies here, maybe it comes down to how
many times you do a layout each year, and how much you enjoy that sort
of work. I definitely think it's something you have to do fairly often
to keep your chops up.

Andy, I'd also like to hear more about your pin-swap FPGA design flow
- what tools do that? Also curious about any timing issues that have
been caught after the pin-swap.

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.

Also, just out of curiosity, how many of you do your own PCB layout,
versus farming it out? It would certainly save us a lot of money to
buy the tools and do it ourselves, but it seems like laying out a
board out well requires quite a bit of experience, especially a 6-8
layer board with high pin count FPGA's.

We're just setting up a hardware shop here, and although I've been
doing FPGA and board schematics design for a while, it's always been
at a larger company with resources to farm the layout out, and we
never did anything high-speed to really worry about the board layout
too much. Thanks in advance for your opinions.

Joel Koltner wrote:


Totally insuitable for serious applications? Oh man. Let's see, what
have we here? A 418MHz transmitter, several matching networks, a UHF
receiver ... all on phenolic.

Sometimes I wish that professors had more nose-to-the-grindstone
industry work under the belt. I mean real design work where cost is a
big factor. Otherwise they are going to tell students they should use
Rogers for just about everything ...
Don't forget rogers is not perfect , intolerance to flexing and

On Thu, 17 Apr 2008 09:43:09 -0700 (PDT), Dave <dhschetz@gmail.com
wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.

What's the brute force method? We preassign most fpga pins for clean,
no-crossover routing to other chips. We discuss the general issues,
especially placement, with our pcb layout guy and he actually decides
which pins go where. Then he back-annotates the schematic and gives us
a file we can use to create the fpga pin constraints file. Sometimes
bank issues complicate the process, but it works pretty well.

Also, just out of curiosity, how many of you do your own PCB layout,
versus farming it out? It would certainly save us a lot of money to
buy the tools and do it ourselves, but it seems like laying out a
board out well requires quite a bit of experience, especially a 6-8
layer board with high pin count FPGA's.

We'd never farm it out. We do critical mixed-signal stuff, and need to
be near our layout guy constantly. He puts up a version on our server
daily at least, and we keep an eye on progress. And we have a lot of
mini-meetings to change the rules as needed. Besides, we have evolved
some styles (and libraries!) that we couldn't very well transfer to a
service bureau. PCB layout is too important to farm out.

We're just setting up a hardware shop here, and although I've been
doing FPGA and board schematics design for a while, it's always been
at a larger company with resources to farm the layout out, and we
never did anything high-speed to really worry about the board layout
too much. Thanks in advance for your opinions.


For really critical stuff, sometimes I'll take over and route that
part of the board myself. It's just too hard to communicate exactly
what I want.